Active transport of l-sorbose and 2-deoxy-d-galactose in Saccharomyces fragilis

Sorbose and 2-deoxy-d-galactose are taken up in Saccharomyces fragilis by an active transport mechanism, as indicated by the energy requirement of the process and the accumulation of free sugar against the concentration gradient. There are no indications for transport-associated phosphorylation as mechanism of energy coupling with these two sugars.The measured sugar-proton cotransport and the influx inhibition by uncouplers suggest a chemiosmotic coupling mechanism. Thus there are at least two different active transport mechanisms operative in Saccharomyces fragilis: transport-associated phosphorylation in the case of 2-deoxy-d-galactose and chemiosmotic coupling in the case of sorbose and 2-deoxy-d-galactose. The difference between the two mechanisms are discussed.Uncouplers do not stimulate downhill sorbose transport in energy-depleted cells and evoke an almost complete inhibition of efflux and of exchange transport.The differences between this sugar-proton cotransport system and similar systems in bacteria and Chlorella are discussed.     

Ataxia-telangiectasia: a variant with altered in vitro phenotype of fibroblast cells

The clinical and cellular phenotype of ataxia telangiectasia (AT) has been extensively documented in numerous patients of different ethnic groups and is characterized by several specific laboratory hallmarks, such as chromosomal instability, profound radiosensitivity and radioresistant DNA synthesis. Several recent reports have, however, shown variations on this theme. This article describes 2 Turkish siblings with AT, who showed a typical but somewhat more prolonged clinical course of the disease and altered characteristics of fibroblasts cells, compared to the ‘classical’ AT cellular phenotype. Fibroblasts strains derived from these patients showed a normal cellular life span, moderate degrees of chromosomal instability and sensitivity to the lethal effects of X-rays and neocarzinostatin, and lack of radioresistant DNA synthesis.

A compilation of the literature on ‘AT variants’ and ‘AT-like’ syndromes shows that in addition to the internal variability of AT, this disease occupies a limited segment within a large spectrum of clinical and cellular features, which are common to a variety of syndromes. Each of these syndromes covers a different segment in this spectrum. The genetic basis of this family of disorders might be complex.     

Characterization of gamma-glutamylamidase-glutaminase activity in Saccharomyces cerevisiae

In a foregoing paper we have shown the presence in the yeast Saccharomyces cerevisiae of an enzyme catalyzing the hydrolysis of L-gamma-glutamyl-p-nitroanilide, but apparently distinct from gamma-glutamyltranspeptidase. The cellular level of this enzyme was not regulated by the nature of the nitrogen source supplied to the yeast cell. Purification was attempted, using ion exchange chromatography on DEAE Sephadex A 50, salt precipitations and successive chromatographies on DEAE Sephadex 6B and Sephadex G 100. The apparent molecular weight of the purified enzyme was 14,800 as determined by gel filtration. As shown by kinetic studies and thin layer chromatography, the enzyme preparation exhibited only hydrolytic activity against gamma-glutamylarylamide and L-glutamine with an optimal pH of about seven. Various gamma-glutamylaminoacids, amides, dipeptides and glutathione were inactive as substrates and no transferase activity was detected. The yeast gamma-glutamylarylamidase was activated by SH protective agents, dithiothreitol and reduced glutathione. Oxidized glutathione, ophtalmic acid and various gamma-glutamylaminoacids inhibited competitively the enzyme. The activity was also inhibited by L-gamma-glutamyl-o-(carboxy)phenylhydrazide and the couple serine-borate, both transition-state analogs of gamma-glutamyltranspeptidase. Diazooxonorleucine, reactive analog of glutamine, inactivated the enzyme. The physiological role of yeast gamma-glutamylarylamidase-glutaminase is still undefined but is most probably unrelated to the bulk assimilation of glutamine by yeast cells.     

Quercetin prevents osteoarthritis progression possibly via regulation of local and systemic inflammatory cascades

Due to the lack of effective treatments, osteoarthritis (OA) remains a challenge for clinicians. Quercetin, a bioflavonoid, has shown potent anti-inflammatory effects. However, its effect on preventing OA progression and the underlying mechanisms are still unclear. In this study, Sprague–Dawley male rats were divided into five groups: control group, OA group (monosodium iodoacetate intra-articular injection), and three quercetin-treated groups. Quercetin-treated groups were treated with intragastric quercetin once a day for 28 days. Gross observation and histopathological analysis showed cartilage degradation and matrix loss in the OA group. High-dose quercetin-group joints showed failure in OA progression. High-dose quercetin inhibited the OA-induced expression of MMP-3, MMP-13, ADAMTS4, and ADAMTS5 and promoted the OA-reduced expression of aggrecan and collagen II. Levels of most inflammatory cytokines and growth factors tested in synovial fluid and serum were upregulated in the OA group and these increases were reversed by high-dose quercetin. Similarly, subchondral trabecular bone was degraded in the OA group and this effect was reversed in the high-dose quercetin group. Our findings indicate that quercetin has a protective effect against OA development and progression possibly via maintaining the inflammatory cascade homeostasis. Therefore, quercetin could be a potential therapeutic agent to prevent OA progression in risk groups.     

Offspring Defence in Relation to Litter Size and Age: Experiment in the Bank vole Clethrionomys glareolus

According to parental investment theory, nest defence activity should be related to the reproductive value of the offspring. Alternative hypotheses suggest that defence activity may, for example, depend upon the conspicuousness of the young. Studies concerning this topic have been carried out almost exclusively on birds and experimental data on the diversity of organisms is lacking. Bank voles Clethrionomys glareolus were used to study the effects of the number and age of offspring upon the pup defence activity of mothers. Male bank voles are infanticidal and thus an adult male was used as a predator. Defence trials were conducted in the laboratory and filmed for subsequent analysis. Litter sizes were divided into three treatment groups: reduced (−2 pups), control (±0 pups) and enlarged (+2 pups). In order to study the effect of offspring age upon maternal defence activity the trials were conducted twice: when the pups were 3 and 8 days old. Defence activity increased with the number of offspring and enlarged litters were most actively defended. This result supports parental investment theory and conclusions drawn by earlier studies of birds. However, in contrast to the conclusions of earlier studies, older offspring were defended less than the younger ones. Whilst new-born pups are totally defenceless against predators their vulnerability decreases as they age. Therefore, we suggest that maternal aggression in female bank voles is related to the value as well as to the vulnerability of the offspring. The validity of this explanation and the determinants of parental investment decisions in small mammals in general deserve further study. This revised version was published online in July 2006 with corrections to the Cover Date.     

Sequence homologies between type 1 and type 2A protein phosphatases

The Mr = 33,000 catalytic fragment of rabbit skeletal muscle type 1 protein phosphatase was digested with trypsin after reduction and alkylation. The resulting peptides were isolated, subjected to automated Edman degradation, and their sequences compared to the deduced peptide sequence of the bovine type 2A protein phosphatase cDNA. Of 10 tryptic peptides from the type 1 phosphatase that were sequenced, nine showed a high degree of homology with the type 2A phosphatase. This provides the first direct sequence comparison suggesting that the type 1 and type 2 protein phosphatases, distinguished functionally by their substrate specificities and sensitivity to inhibitors, make up part of a family of closely related gene products with similar structures.     

Adsorption effects in the decolorization of a Kraft bleach plant effluent by Phanerochaete chrysosporium

Summary Phanerochaete chrysosporium was proposed for the decolorization and degradation of chlorinated compounds (AOX) present in the E1 stage effluent of the Kraft process. We observed that pellets of the fungus inoculated in the E1 effluent, not supplemented with nutrients, strongly absorb colour and AOX. The data were in agreement with a model describing a multilayer adsorption.