Co-distribution of annexin VI and actin in secretory ameloblasts and odontoblasts of rat incisor

Summary Annexin VI and actin were detected by immunoblot analysis in the enamel- and dentin-related portions of dental tissues. Annexin VI was found mainly in the particulate fraction whereas actin was detected in both the soluble and particulate fractions. By immunoelectron microscopy, annexin VI antibodies conjugated with colloidal gold were seen to label the mitochondria, the cytosol and the nucleus of secretory ameloblasts and odontoblasts of rat incisor. In the processes of these cell, the plasmalemmal undercoat was labeled. Antiactin antibodies labeled the desmosome-like junctions, the cytosol, and the mitochondria of the cell bodies. Extensive labeling was seen at the periphery of the Tomes' processes and odontoblast processes. These results suggest that annexin VI may play a role in Ca²⁺-regulation in the cell bodies, especially as a calcium receptor protein in the mitochondria. Moreover, annexin VI and actin seem to be co-distributed in secretory processes. Thus, these proteins might be both involved in exocytotic and endocytotic events.     

Metabolism and Solubilization of Cellulose by Clostridium cellulolyticum H10

When Clostridium cellulolyticum was grown with cellulose MN300 as the substrate, the rates of growth and metabolite production were found to be lower than those observed with soluble sugars as the substrate. At low cellulose concentrations, the growth yields were equal to those obtained with cellobiose. The main fermentation products from cellulose and soluble sugars were the same. Up to 15 mM of consumed hexose, a change in the metabolic pathway favoring lactate production similar to that observed with soluble sugars was found to occur concomitantly with a decrease in molar growth yield. With cellulose concentrations above 5 g/liter, accumulation of soluble sugars occurred once growth had ceased. Glucose accounted for 30% of these sugars. A kinetic analysis of cellulose solubilization revealed that cellulolysis by C. cellulolyticum involved three stages whatever cellulose concentration was used. Analysis of these kinetics showed three consecutive enzymatic activity levels having the same K_m (0.8 g of cellulose per liter, i.e., 5 mM hexose equivalent) but decreasing values of V_max. The hypothesis is suggested that each step corresponds to differences in cellulose structure.     

The behaviour of Dutch fresh water ecologists in response to environmental concern

Due to the rise of environmental concern ecologists have been asked for advice more frequently since the late 1960s. This article discusses how the changing relationship between ecologists and society has affected the behaviour of one particular group of ecologists, namely Dutch fresh water ecologists, by focussing on their behaviour towards job market control and public interest activities. The analysis has been based on interviews with 65 Dutch fresh water ecologists together with an analysis of their publications.In contrast with American ecologists, Dutch fresh water ecologists have made little effort to control their job market by formal arrangements such as formulating a code of ethics and certification procedures. Secondly, Dutch fresh water ecologists generally conceive of their own role in contributing to the solution of environmental problems in relation to that of the environmentalists by doing good research and reliable advisory work. Although a significant number of researchers also address lay publics by writing popular articles and/or holding lectures, only a minority actively participates in environmental politics.     

Absence of genotoxic effects of nonasbestos mineral fibers

The biological activity of natural and synthetic mineral fibers has been examined. Natural attapulgite [(Mg, Al)₂Si₄O₁₀(OH).4H₂0], synthetic xonotlite [Ca₃Si₃O₈(OH)₂] and natural sepiolite [Mg₂Si₃O₈.2H₂O] were selected. Genotoxic effects were investigated by means of a well established cellular model based upon the measurement of unscheduled DNA synthesis (UDS) in rat hepatocytes in primary culture. The intrinsic capacity of the fibers (1 and 10 µ/ml) to induce UDS was first tested. None of the fiber types showed detectable UDS-eliciting activity. Also, the possible modulation of the cellular response to genotoxic agents by the materials was examined by exposing the cells to mixtures of 2-acetylaminofluorene (AAF) (0.05 and 0.25 µg/ml) and fibers (1 and 10 µg/ml). In these experiments, the UDS response was significantly diminished in the presence of xonotlite. This phenomenon may reflect changes in the uptake and/or metabolism of AAF or may result from an inhibition of DNA repair processes, the latter suggesting a possible cocarcinogenic potential for this synthetic silicate. These results point to the immediate necessity of studying more extensively the biological effects of fibrous materials that can be used as substitutes for asbestos.Abbreviations AAF 2-acetylaminofluorene - DMSO dimethyl-sulfoxide - FBS fetal bovine serum - IRDA Institut de Recherche et de Développement sur l'Amiante - LDH lactate dehydrogenase - UDS unscheduled - DNA synthesis - WME Williams' Medium E This work was supported by the Institut de Recherche et de Développement sur l'Amiante (IRDA), Sherbrooke, Canada.     

Energy conservation in whole cells of the methylotrophic bacterium Methylophilus methylotrophus

Respiratory chain phosphorylation has been investigated in the methylotrophic bacterium Methylophilus methylotrophus following the addition of oxidisable substrates to aerobic, whole cell suspensions. Initial-rate experiments showed that ATP synthesis occurred at the overall expense of AMP and inorganic phosphate via the sequential action of the ATP phosphohydrolase and adenylate kinase; some of the nascent ATP was rapidly used to synthesis nonadenine nucleoside triphosphates. After being corrected for ATP turnover, Pi/O quotients of 0.46 to 0.54, 0.77 and 1.37 nmol/ng-atom O were obtained for the oxidation of methanol dehydrogenase-linked substrates (methanol, ethanol and acetaldehyde), duroquinol and formate (NAD⁺-linked) respectively. These values were proportional to the H⁺/O and/or K⁺/O quotients exhibited by these substrates, and yielded an average H⁺/ATP (H⁺/Pi) quotient of 4.2 ng-ion H⁺/nmol. Steady-state experiments showed that the extent of cellular energisation varied with the respiration rate but was always in the order methanol > duroquinol > acetaldehyde, thus indicating that under these longer-term conditions methanol was completely oxidised to yield PQQH₂ and 2NAD(P)H. These results are discussed in terms of the various reactions which lead to the generation or utilisation of the protonmotive force in this organism.Abbreviations FCCP carbonylcyanide p-trifluoromethyxyphenyl-hydrazone - bulk phase, transmembrane electrochemical potential difference of protons ( ) - pH bulk phase, transmembrane pH difference (pH_in–pH_out) - bulk phase, transmembrane electrical potential difference (_in - _out) - [P] concentration of anhydride phosphate bonds in adenine nucleotides (2[ATP]+[ADP]) - FPLC fast protein liquid chromatography - PQQ pyrroloquinoline quinone - Gp phosphorylation potential     

Laryngeal papillomas: local cellular immune response,keratinization and viral antigen

Virchows Archiv B Cell Pathology - Various parameters of the local cellular response have been studied in 16 laryngeal papillomas from ten patients with recurrent papillomas as well as normal...     

Chronic toxicity of three insecticides (carbaryl,fenthion and lindane) in the freshwater snail Lymnaea stagnalis

A chronic intoxication with carbaryl, fenthion and lindane was induced in young snails. The parameter k of the von Bertalanffy's equation showed clearly the growth changes induced by these insecticides. In all cases the fecundity of intoxicated snails was reduced. Among these three insecticides, lindane was the most toxic, carbaryl the least.     

Toxicité aiguë d'un fongicide dithiocarbamate,le thirame,chez des larves de l'ephémère Cloeon dipterum: effets de divers paramètres

Acute toxicity and degradation of an aqueous suspension of Thiram were studied in Cloeon dipterum. Lethal concentrations for 50% of the larvae (LC 50) after 24 to 96 h of exposure and thresholds were calculated. LC 50 varied from 0.39 to 1.92 mg·l^?1 according to the time and the physiological state of the larvae. It was demonstrated that:

the sensitivity of the larvae increased with the time during which they were kept in the laboratory;

while the toxicity of the aqueous suspension (1 mg·l^?1) of Thiram decreased with time, another toxic product was formed.

     

Pro-opiomelanocortin peptides in the human fetal pituitary

Levels of immunoreactive pro-opiomelanocortin (POMC) peptides (N- and C-terminal ACTH, N- and C-terminal LPH and α-MSH) have been measured in pituitary extracts from human fetuses of 12–22 weeks gestation. The levels of ACTH were 30–200 times higher than α-MSH in all fetuses studied. Sephadex G-75 and G-25 chromatography of 8 extracts showed peaks of 34 kilodaltons (K) POMC, 22K ACTH, β-LPH, γ-LPH, β-endorphin, approximately 8K ACTH, 1–39 ACTH, α-MSH and CLIP. The 8K and 22K forms of ACTH are both partly glycosylated.In vitro culture of pituitaries from 2 fetuses (22 and 26 weeks gestation) gave a detectable basal output of ACTH but not of α-MSH. Stimulation of these pituitary cells with human fetal and rat hypothalamic extracts and with synthetic ovine CRF-41 produced a significant increase in ACTH release, and either small or undetectable amounts of α-MSH.These results demonstrate the presence of POMC-related peptides in early gestation human fetal pituitaries and suggest that ACTH, and not α-MSH, is the major corticotrophic hormone at this stage of gestation.     

Total Hip Replacement in Osteoarthrosis using the Charnley Prosthesis

Charnley low-friction arthroplasty was performed on 352 osteoarthritic hips, usually because of severe pain. Three hundred and twenty hips were reviewed at a special follow-up clinic or by postal questionnaire. After operation 89% of hips were pain-free or caused only occasional discomfort, and in 76% there was an increased range of movement. Of those patients actually seen for review 79% were judged to have a good or excellent result. The most frequent single complication was deep infection, which occurred in 5·3% of hips.