Rapid method for enumeration of viable Legionella pneumophila and other Legionella spp. in water

A sensitive and specific method has been developed to enumerate viable L. pneumophila and other Legionella spp. in water by epifluorescence microscopy in a short period of time (a few hours). This method allows the quantification of L. pneumophila or other Legionella spp. as well as the discrimination between viable and nonviable Legionella. It simultaneously combines the specific detection of Legionella cells using antibodies and a bacterial viability marker (ChemChrome V6), the enumeration being achieved by epifluorescence microscopy. The performance of this immunological double-staining (IDS) method was investigated in 38 natural filterable water samples from different aquatic sources, and the viable Legionella counts were compared with those obtained by the standard culture method. The recovery rate of the IDS method is similar to, or higher than, that of the conventional culture method. Under our experimental conditions, the limit of detection of the IDS method was <176 Legionella cells per liter. The examination of several samples in duplicates for the presence of L. pneumophila and other Legionella spp. indicated that the IDS method exhibits an excellent intralaboratory reproducibility, better than that of the standard culture method. This immunological approach allows rapid measurements in emergency situations, such as monitoring the efficacy of disinfection shock treatments. Although its field of application is as yet limited to filterable waters, the double-staining method may be an interesting alternative (not equivalent) to the conventional standard culture methods for enumerating viable Legionella when rapid detection is required.     

Combined effect of high-pressure treatments and bacteriocin-producing lactic acid bacteria on inactivation of Escherichia coli O157:H7 in raw-milk cheese

The effect of high-pressure (HP) treatments combined with bacteriocins of lactic acid bacteria (LAB) produced in situ on the survival of Escherichia coli O157:H7 in cheese was investigated. Cheeses were manufactured from raw milk inoculated with E. coli O157:H7 at approximately 10(5) CFU/ml. Seven different bacteriocin-producing LAB were added at approximately 10(6) CFU/ml as adjuncts to the starter. Cheeses were pressurized on day 2 or 50 at 300 MPa for 10 min or 500 MPa for 5 min, at 10 degrees C in both cases. After 60 days, E. coli O157:H7 counts in cheeses manufactured without bacteriocin-producing LAB and not pressurized were 5.1 log CFU/g. A higher inactivation of E. coli O157:H7 was achieved in cheeses without bacteriocin-producing LAB when 300 MPa was applied on day 50 (3.8-log-unit reduction) than if applied on day 2 (1.3-log-unit reduction). Application of 500 MPa eliminated E. coli O157:H7 in 60-day-old cheeses. Cheeses made with bacteriocin-producing LAB and not pressurized showed a slight reduction of the pathogen. Pressurization at 300 MPa on day 2 and addition of lacticin 481-, nisin A-, bacteriocin TAB 57-, or enterocin AS-48-producing LAB were synergistic and reduced E. coli O157:H7 counts to levels below 2 log units in 60-day-old cheeses. Pressurization at 300 MPa on day 50 and addition of nisin A-, bacteriocin TAB 57-, enterocin I-, or enterocin AS-48-producing LAB completely inactivated E. coli O157:H7 in 60-day-old cheeses. The application of reduced pressures combined with bacteriocin-producing LAB is a feasible procedure to improve cheese safety.     

Cell architecture during gametophytic and embryogenic microspore development in <Emphasis Type="Italic">Brassica napus</Emphasis> L.

In this work, the cell architecture of the microspore following both gametophytic and embryogenic developmental pathways in vitro was compared with the gametophytic development in vivo in Brassica napus, at both light and electron microscopy level. The microspore reprogramming to embryogenesis involves defined changes affecting cell activities and structural organization which can be considered as markers of the microspore embryogenic pathway, but less is known about others developmental programmes followed by the microspore in vitro after both, inductive and non-inductive conditions. Low-temperature processing of the samples, cytochemical and immunocytochemical approaches to identify various cell components were performed. Differences in specific cellular features such as cellular size and shape, nuclear architecture, starch accumulation, presence of vacuoles and ribosomal population were studied to characterize sequential stages of microspore embryogenesis and other pathways occurring in vitro. The presence of abundant starch grains in a defined cytoplasmic region appeared as a specific feature of the in vitro gametophytic development, as well as of the non-induced microspores of in vitro cultures under embryogenic-inductive conditions.     

Intracellular Ca2+ dynamics in malignant hyperthermia and central core disease: established concepts, new cellular mechanisms involved

Malignant hyperthermia (MH) and central core disease (CCD) are inherited human disorders of skeletal muscle Ca2+ homeostasis. Both MH and CCD are linked to mutations and/or deletions in the gene encoding the skeletal muscle ryanodine receptor (RyR1), the intracellular Ca2+ release channel, which is essential to excitation-contraction (EC) coupling. Our knowledge on how mutations in RyR1 disrupt intracellular Ca2+ homeostasis and EC coupling, eventually leading to MH and CCD has been recently improved, thanks to multidisciplinary studies ranging from clinical, single channel recordings, patch-clamp experiments, and molecular biology. This review presents a brief historical perspective, on how pioneer studies resulted in associating MH and CCD to RyR1. The review is also focused on discussing novel results in regard to pathophysiological consequences of specific MH/CCD RyR1 mutant proteins, which are representative of the different cellular mechanisms that are linked to either phenotype.     

Rho GTPase expression in tumourigenesis: evidence for a significant link

Rho proteins belong to the small GTPases superfamily. They function as molecular switches that, in response to diverse stimuli, control key signaling and structural aspects of the cell. Although early studies proposed a role for Rho GTPases in cellular transformation, this effect was underestimated due to the fact that no genetic mutations affecting Rho-encoding genes were found in tumors. Recently, it has become evident that Rho GTPases participate in the carcinogenic process by either overexpression of some of the members of the family with oncogenic activity, downmodulation of other members with suggested tumor suppressor activity, or by alteration of upstream modulators or downstream effectors. Thus, alteration of the levels of expression of different members of the family of Rho GTPases has been detected in many types of human tumors leading to a great interest in the cellular effects elicited by these oncoproteins. This essay reviews the current evidence of dysregulation of Rho signaling by overexpression in human tumors.     

Neurotoxic dopamine quinone facilitates the assembly of tau into fibrillar polymers

Aberrant aggregation of microtubule associated protein tau is the main characteristic of different disorders known as tauopathies. Different compounds have been described to facilitate tau aberrant aggregation. In this work, we demonstrate that oxidized products of dopamine (neurotoxic dopamine quinone), a neurotransmitter involved in Parkinson's disease, promote tau polymerization. Curiously, neurons expressing dopamine (substantia nigra) show a low content of tau protein and seldom have tau aggregation in tauopathies. In non-dopaminergic neurons, quinone oxidation products may be involved in tau polymerization. These results support a link between oxidative damage and the onset of tauopathies. (Mol Cell Biochem 278: 203–212, 2005)     

Tendon xanthomas in familial hypercholesterolemia are associated with a differential inflammatory response of macrophages to oxidized LDL

Tendon xanthomas (TX) are pathognomonic lipid deposits commonly found in familial hypercholesterolemia (FH) patients. The aim of this study was to determine whether macrophages from FH patients with TX (TX+) have higher predisposition to foam cells formation after oxidized LDL (oxLDL) overload than those from FH patients without TX (TX-), and if their differential gene expression profile could explain these different phenotypes. Total RNA pools from macrophages from FH patients TX+ and TX- were analyzed using Affymetrix oligonucleotide arrays to evaluate the gene expression profile in presence and absence of oxLDL. Also, the intracellular lipid content was measured by fluorescence flow cytometry. Results of these studies suggest that macrophages from FH subjects TX+ compared to those TX- have a differential response to oxLDL, since they show higher intracellular cholesterol ester accumulation and a differential gene expression profile. The gene array data were validated by relative quantitative real-time RT-PCR and quantitative ELISA in culture media and plasma samples. FH subjects TX+ showed increased plasma tryptase, TNF-alpha, IL-8 and IL-6 concentrations. We propose that TX formation are associated with higher intracellular lipid content, and higher inflammatory response of macrophages in response to oxLDL.     

Oxidative imbalance in alzheimer’s disease

Oxidative stress is a striking feature of susceptible neurons in the Alzheimer’s disease brain. Importantly, because oxidative stress is an early event in Alzheimer’s disease, proximal to the development of hallmark pathologies, it likely plays an important role in the pathogenesis of the disease. Investigations into the cause of such oxidative stress show that interactions between abnormal mitochondria and disturbed metal metabolism are, at least in part, responsible for cytoplasmic oxidative damage observed in these susceptible neurons, which could ultimately lead to their demise. Oxidative stress not only temporally precedes the pathological lesions of the disease but could also contribute to their formation, which, in turn, could provide some protective mechanism to reduce oxidative stress and ensure that neurons do not rapidly succumb to oxidative insults. In this review, we present the evidence for oxidative stress in Alzheimer’s disease and its likely sources and consequence in relation to other pathological changes.     

In vivo inhibition of endogenous brain tumors through systemic interference of Hedgehog signaling in mice

The full spectrum of developmental potential includes normal as well as abnormal and disease states. We therefore subscribe to the idea that tumors derive from the operation of paradevelopmental programs that yield consistent and recognizable morphologies. Work in frogs and mice shows that Hedgehog (Hh)-Gli signaling controls stem cell lineages and that its deregulation leads to tumor formation. Moreover, human tumor cells require sustained Hh-Gli signaling for proliferation as cyclopamine, an alkaloid of the lily Veratrum californicum that blocks the Hh pathway, inhibits the growth of different tumor cells in vitro as well as in subcutaneous xenografts. However, the evidence that systemic treatment is an effective anti-cancer therapy is missing. Here we have used Ptc1(+/-); p53(-/-) mice which develop medulloblastoma to test the ability of cyclopamine to inhibit endogenous tumor growth in vivo after tumor initiation through intraperitoneal delivery, which avoids the brain damage associated with direct injection. We find that systemic cyclopamine administration improves the health of Ptc1(+/-);p53(-/-) animals. Analyses of the cerebella of cyclopamine-treated animals show a severe reduction in tumor size and a large decrease in the number of Ptc1-expressing cells, as a readout of cells with an active Hu-Gli pathway, as well as an impairment of their proliferative capacity, always in comparison with vehicle treated mice. Our data demonstrate that systemic treatment with cyclopamine inhibits tumor growth in the brain supporting its therapeutical value for human HH-dependent tumors. They also demonstrate that even the complete loss of the well-known tumor suppressor p53 does not render the tumor independent of Hh pathway function.