Cardiovascular screening for men at high risk in Heart of Birmingham Teaching Primary Care Trust: the 'Deadly Trio' programme

BACKGROUND

The Deadly Trio programme offered cardiovascular health checks to men over 40 in inner-city Birmingham. The aim was to increase diagnosis of diabetes, cardiovascular and kidney disease among this deprived and ethnically diverse population. Either patients' own general practitioners (GPs) were paid to provide health checks or patients were invited to an alternative provider.

METHODS

Routine data were sought from 68 participating practices. Logistic regression analysis was undertaken to determine the patient and practice factors associated with being screened and with being added to a disease register.

RESULTS

Data were obtained from 58 practices; 5871 (24.3%) of 24 166 eligible men were screened. Screening uptake was higher in those with a recorded phone number, South Asians and Blacks but lower in smokers. Compared to the alternative provider, uptake was higher among men registered with single-handed (but not multi-partner) GPs paid to provide health checks. South Asian, older and screened men were more often added to disease registers. Men with missing information and GP-screened men were less likely to be added to registers.

CONCLUSIONS

The programme achieved higher screening uptake and diagnosis of disease among minority ethnic men. Single-handed GPs paid to provide screening (and their patients) were more responsive than multi-partner practices.

Developmental toxicity of combined ethylbenzene and methylethylketone administered by inhalation to rats

Pregnant Sprague-Dawley rats were exposed to ethylbenzene (EB; 0, 250, or 1000 ppm) and methylethylketone (MEK; 0, 1000, or 3000 ppm), alone and in combination, by inhalation, for 6h/day, during days 6-20 of gestation. Maternal toxicity, evidenced by decreased in body weight gain and food consumption, tended to be greater after simultaneous exposures to the high concentrations of 1000 ppm EB and 3000 ppm MEK, when compared to the treatments with individual compounds. No significant increase in embryo/fetal lethality or incidence of malformations and variations was observed in any of the treatment groups. Fetal body weight was significantly reduced after individual treatment with 1000 ppm EB or 3000 ppm MEK, and in the combined groups. There was no evidence of interaction between EB and MEK in causing developmental toxicity.

Higher plant cells: gamma-tubulin and microtubule nucleation in the absence of centrosomes

The assembly of the higher plant cytoskeleton poses several fundamental questions. Since different microtubule arrays are successively assembled during the cell cycle in the absence of centrosomes, we can ask how these arrays are assembled and spatially organized. Two hypotheses are under debate. Either multiple nucleation sites are responsible for the assembly and organization of microtubule arrays or microtubule nucleation takes place at one site, the nuclear surface. In the latter case, microtubule nucleation and organization would be two distinct but coregulated processes. During recent years, novel approaches have provided entirely new insights to understand the assembly and dynamics of the plant cytoskeleton. In the present review, we summarize advances made in microscopy and in molecular biology which lead to novel hypotheses and open up new fields of investigation. From the results obtained, it is clear that the higher plant cell is a powerful model system to investigate cytoskeletal organization in acentrosomal eukaryotic cells.

Characterization of microsome-associated tobacco BY-2 centrins

Centrin - higher plants - MTOCs - microtubules nucleation In most eukaryotic cells, the Ca(2+)-binding protein centrin is associated with structured microtubule-organizing centers (MTOCs) such as centrosomes. In these cells, centrin either forms centrosome-associated contractile fibers, or is involved in centrosome biogenesis. Our aim was to investigate the functions of centrin in higher plant cells which do not contain centrosome-like MTOCs. We have cloned two tobacco BY-2 centrin cDNAs and we show that higher plant centrins define a phylogenetic group of proteins distinct from centrosome-associated centrins. In addition, tobacco centrins were found primarily associated with microsomes and did not colocalize with gamma-tubulin, a known MTOC marker. While the overall level of centrin did not vary during the cell cycle, centrin was prominently detected at the cell plate during telophase. Our results suggest that in tobacco, the major portion of centrin is not MTOC-associated and could be involved in the formation of the cell plate during cytokinesis.

Evaluation of rat hepatic 2E1 activity in function of age, sex and inducers: choice of an experimental model capable of testing the hepatotoxicity of low molecular weight compounds

The aim of this work on rat hepatic P450 2E1 activity was to seek the most suitable experimental model to study the role of cytochrome P450 2E1 in the metabolism of industrial chemicals. Two sets of experiments were devoted to selecting the age and sex of animals and to estimating the response of male and female rats to different inducers. In the first set, the effect of three inducers (fasting; ethanol; acetone) was studied in male rats aged 5, 7 and 9 weeks. In the second set, the effect of different inducers, namely beta-naphthoflavone (BNF), phenobarbital (PB), ethanol, acetone and pyridine, on PNP and chlorzoxazone (CLZO) hydroxylase activities was studied in 7 week old male and female rats. The results demonstrate firstly that microsomal p-nitrophenol (PNP) hydroxylase activity significantly decreases in control male rats in inverse function of age, and secondly that induction by ethanol decreases with age. The PNP hydroxylase activity level of controls and the significant increases in PNP hydroxylase activity observed in 7 week old male rats show that this is the most suitable age for the second set of experiments. In this second set, it was shown that P450 1A (induced by BNF) is involved in CLZO hydroxylase activity only. PB increased the hydroxylase activities in male and female rats by about 1.5 and 1.7 times those of the controls, respectively. The effects of P450 2E1 inducers in function of sex show that male rats exhibited more significant increases in PNP and CLZO hydroxylase activities than female. The specificity of these two substrates is discussed. Neither of these two reactions was specifically catalysed by P450 2E1, but PNP may be considered as the most specific and the least sensitive substrate. In addition, the linear relationship observed between the two substrates (PNP and CLZO) showed a good correlation between their activities (r = 0.90, P < 0.001). In conclusion, these results suggest the use of the 7 week old male rat as the experimental model to study the role of cytochrome P450 2E1 in the hepatotoxicity of low molecular weight industrial chemicals.

Tobacco BY-2 cell-free extracts induce the recovery of microtubule nucleating activity of inactivated mammalian centrosomes

The structure and the molecular composition of the microtubule-organizing centers in acentriolar higher plant cells remain unknown. We developed an in vitro complementation assay where tobacco BY-2 extracts can restore the microtubule-nucleating activity of urea-inactivated mammalian centrosomes. Our results provide first evidence that soluble microtubule-nucleating factors are present in the plant cytosolic fraction. The implication for microtubule nucleation in higher plants is discussed.

The role of glutathione and cysteine conjugates in the nephrotoxicity of o-xylene in rats

Moderate nephrotoxicity was induced in male and female rats exposed to o-xylene for 4 h at atmospheric concentrations of approximately 3000 ppm. The xylene in vivo nephrotoxicity resulted in low enzyme leakage from the kidney into the urine. This low leakage was confirmed in 24-h urine by an increase in gamma-glutamyltranspeptidase (gammaGT), N-acetyl-beta-D-glucosaminidase (NAG) and alkaline phosphatase (ALP) activities. Compared to the control, both the 24-h urine output and the glucose excretion increased in male and female rats. These increases were probably a result of damage to the renal proximal tubules. The role of the metabolic pathway of glutathione in the emergence of the renal damage observed with o-xylene was investigated in rats. Recent studies indicate that the metabolic pathway of glutathione may be a bioactivation pathway, which is responsible for nephrotoxic effects with several drugs or chemicals. The renal toxicity of three synthesized o-xylene thio-conjugates was investigated in several groups of female rats. Administration of S-(o-methylbenzyl)glutathione (i.p., 1 mmol/kg), S-(o-methylbenzyl)cysteine (per os, 1 mmol/kg) or N-acetyl-S-(o-methylbenzyl)cysteine (i.p., 0.75 mmol/kg) to female rats did not induce renal toxicity, as monitored by urinary biochemical parameters (gammaGT, NAG, ALP, glucose). The data obtained suggest that the glutathione pathway would appear to be only detoxication, and probably does not contribute to the renal toxicity of o-xylene in female rats. Thus, either another metabolic pathway or other intermediate metabolites are probably involved in the nephrotoxic action of o-xylene.

The growing cell plate of higher plants is a site of both actin assembly and vinculin-like antigen recruitment

Compelling evidence supports the idea that actin filaments play an active role in the cytokinetic process of higher plant cells. However, the mechanisms that control the growth of the cell plate and its stabilization remain so far unknown. We show that a novel population of short actin filaments continuously assembles in the phragmoplast at the growing cell plate. Microinjection of rhodamine-phalloidin during these final stages of telophase revealed the dynamic assembly and organization of these actin filaments during vesicle fusion. Comparable data were obtained in endosperm syncytia during the development of the cell plate between non sister nuclei, i.e. independently of the formation of the mitotic phragmoplast. Concomitantly, plant polypeptides sharing epitopes with human vinculin are revealed within the forming cell plate, suggesting their recruitment during cytokinesis-associated actin assembly. These vinculin-like antigens may participate in membrane/F-actin anchorage protein complexes. Our data, in addition to the identification of plant integrin homologues reported by several authors, suggest the existence of a cell wall/extracellular matrix/plasma membrane/actin cytoskeleton continuum. Such an architecture may control cell-cell interactions during cell plate formation and may contribute to the establishment of polarity in higher plants.

Interactive effect of combined exposure to glycol ethers and alcohols on toxicodynamic and toxicokinetic parameters

Ethylene glycol monomethyl ether (EGME) exhibits testicular toxicity and ethylene glycol monobutyl ether (EGBE) is a solvent with haemolytic effects in rats. The study of the interaction of two glycol ethers (EGME and EGBE) and three alcohols (ethanol, n-propanol and n-butanol, 10 or 30 mmol/kg), orally co-administered in male rats, was carried out from a toxicodynamic and toxicokinetic point of view. Administered alone, EGME (10 mmol/kg) caused a 30- and 5-fold increase in the urinary creatine/creatinine ratio at 24 and 48 h, respectively, and 24 h urinary excretion of methoxyacetic acid was of 0.71 +/- 0.042 mmol 24 h (mean +/- SE). The simultaneous administration of one of the three alcohols at either of the doses mentioned above did not significantly modify the urinary creatine/creatinine ration (24 and 48 h), or the 24 h urinary excretion of methoxyacetic acid. Administered alone, EGBE (5 mmol/kg) caused an average decrease of 26% in the number of circulating red blood cells and a strong (250 times) increase in the level of plasma haemoglobin 4 h after treatment. Urinary excretion of butoxyacetic acid in rats treated with EGBE (1 mmol/kg) was 0.083 +/- 0.0039 mmol/24 h (mean +/- SE). The simultaneous injection of 30 mmol/kg alcohol (ethanol, n-propanol or n-butanol) almost totally inhibits the haemolytic effect of EGBE, and decreases the urinary excretion of butoxyacetic acid by 43-31%. A strong dose of alcohol (30 mmol/kg) decreases the haemolytic effect due to EGBE, and reduces the urinary excretion of butoxyacetic acid. In contrast, the coadministration of alcohol did not modify the testicular toxicity of EGME, or the 24 h urinary excretion of methoxyacetic acid. It is possible that competitive inhibition of alcohol dehydrogenase by alcohols results in the diversion of EGBE metabolism.

Hepatotoxicity of N, N-dimethylformamide in rats following intraperitoneal or inhalation routes of administration

Male Sprague-Dawley rats were administered a single intraperitoneal injection of N, N-dimethylformamide (DMF, 0.01-1.5 g kg-1) or were exposed for 4 h to DMF vapours (75-900 ppm). The serum activities of the enzymes sorbitol deshydrogenase and glutamate deshydrogenase were used as indicators of liver damage, and were determined at 24, 48 or 72 h post-treatment. Following either route of administration DMF caused concentration-dependent elevations in enzyme activities, the maxima of which occurred later after administration of higher concentrations of DMF than after lower concentrations.

The perinuclear microtubule-organizing center and the synaptonemal complex of higher plants share a common antigen: its putative transfer and role in meiotic chromosomal ordering

Recognition of homologous chromosomes during meiotic prophase is associated in most cases with the formation of the synaptonemal complex along the length of the chromosome. Telomeres, located at the nuclear periphery, are preferential initiation sites for the assembly of the synaptonemal complex. In most eukaryotic cells, telomeres cluster in a restricted area, leading to the "bouquet" configuration in leptotene-zygotene, while this typical organization progressively disappears in late zygotene-pachytene. We wondered whether such striking changes in the intranuclear ordering and pairing of meiotic chromosomes during the progression of prophase I could be correlated with activity of the centrosome and/or microtubule-organizing center (MTOC). Plant cells may be used as a model of special interest for this study as the whole nuclear surface acts as an MTOC, unlike other cell types where MTOCs are restricted to centrosomes or spindle pole bodies. Using a monoclonal antibody (mAb 6C6) raised against isolated calf centrosomes we found that the 6C6 antigen is present over the entire surface of the plant meiotic nucleus, in early prophase I, before chromosomal pairing. At zygotene, short fragments of chromosomes become stained near the nuclear envelope and within the nucleus. At pachytene, after complete synapsis, the labeling specifically concentrates within the synaptonemal complexes, although the nuclear surface is no longer reactive. Ultrastructural localization using immunogold labeling indicates that the 6C6 antigen is colocalized with the synaptonemal complex structures. Later in metaphase I, the antigen is found at the kinetochores. Our data favor the idea that the 6C6 antigen may function as a particular "chromosomal passenger-like" protein. These observations shed new light on the molecular organization of the plant synaptonemal complex and on the redistribution of cytoskeleton-related antigens during initiation of meiosis. They suggest that antigens of MTOCs are relocated to chromosomes during the synapsis process starting at telomeres and contribute to the spatial arrangement of meiotic chromosomes. Such cytoskeleton-related antigens may acquire different functions depending on their localization, which is cell-cycle regulated.

Measurement of mode times of flight in multimode fibers by an interferometric method using polychromatic light: theoretical approach and experimental results

The propagation of several modes in an optical fiber is not easy to study. The experiment that we propose permits us to measure the difference in time propagation between two successive modes of a multimode fiber. The same laser beam is coupled into the fiber to be tested and into the reference single-mode fiber. The correlation of output electric fields of the modes propagated by each fiber is realized by an interferometric system.

Plant microtubule-associated proteins (MAPs) affect microtubule nucleation and growth at plant nuclei and mammalian centrosomes

In this study, we investigated the effect of plant microtubule-associated proteins (MAPs) on microtubule nucleation and growth in vitro. Since it has recently been demonstrated that plant nuclear surface acts as a microtubule-organizing center (MTOC), we tested the effects of plant MAPs using a nucleus-mediated microtubule nucleation assay. Nuclei were isolated from interphase tobacco BY-2 cells, and MAPs were isolated from tobacco BY-2 cells at different stages of the cell cycle. The effects of tobacco MAPs on microtubule nucleation at mammalian centrosomes were also analyzed. Under our experimental conditions, both interphase and mitotic tobacco MAPs promoted microtubule assembly around tobacco nuclei and at mammalian centrosomes below the critical tubulin concentration for spontaneous assembly. Interphase tobacco MAPs increase the mean length of nucleated microtubules in proportion to its molar ratio to tubulin. In contrast, mitotic tobacco MAPs do not induce nucleus- and centrosome-mediated nucleation of microtubules in a dose-dependent manner. Both MAP-fractions possessed microtubule bundling activity. The implications of these plant MAP properties on microtubule nucleation in living cells are discussed.

A microtubule-associated protein in maize is expressed during phytochrome-induced cell elongation

Plants can adapt their shape to environmental stimuli. This response is mediated by the reorganization of cortical microtubules, a unique element of the cytoskeleton. However, the molecular base of this response has remained obscure so far. In an attempt to solve this problem, signal-dependent changes in the pattern of microtubule-binding proteins were analysed during coleoptile elongation in maize, that is, under the control of the plant photoreceptor phytochrome. Two putative MAPs of 100 kDa (P100) and 50 kDa apparent molecular weights were identified in cytosolic extracts from non-elongating and elongating cells. Both proteins co-assembled with endogenous tubulin, bound to neurotubules and were immunologically related to the neural MAP tau: the P100 protein, depending on the physiological situation, was manifest as a double band and was always found to be heat-stable. In contrast, the 50 kDa MAP was heat-stable only for particular tissues and physiological treatments. The P100 protein was present in all tissues, however in a reduced amount in elongating coleoptiles. The 50 kDa MAP was expressed exclusively upon induction of phytochrome-dependent cell elongation. As shown by immunofluorescence double-staining, an epitope shared by both proteins colocalized with cortical microtubules in situ, but exclusively in elongating cells. In non-elongating cells, only the nuclei were stained. Partially purified nuclei from elongating cells were enriched in P100, whereas the 50 kDa MAP became enriched in a partially purified plasma membrane fraction.

Cell cycle dependent distribution of a centrosomal antigen at the perinuclear MTOC or at the kinetochores of higher plant cells

Compelling evidence has been obtained in favour of the idea that the nuclear surface of higher plant cells is a microtubule-nucleating and/or organizing site (MTOC), in the absence of defined centrosomes. How these plant MTOC proteins are redistributed and function during the progression of the cell cycle remains entirely unknown. Using a monoclonal antibody (mAb 6C6) raised against isolated calf thymus centrosomes and showing apparent reaction with the plant nuclear surface, we followed the targeted antigen distribution during mitosis and meiosis of higher plants. Immunoblot analysis of protein fractions from Allium root meristematic cell extracts probed with mAb 6C6 reveals a polypeptide of an apparent Mr of 78000. In calf centrosome extracts, a polypeptide of comparable molecular mass is found in addition to a major antigen of Mr 180000 after mAb 6C6 immunoblotting. During mitotic initiation, the plant antigen is prominent on the periphery of the prophase nucleus. When the nuclear envelope breaks down, the antigen suddenly becomes associated with the centromere-kinetochores until late anaphase. In telophase, when the nuclear envelope is being reconstructed, it is no longer detected at the kinetochores but is solely associated again with the nuclear surface. This antigen displays a unique spatial and temporal distribution, which may reflect the pathway of plant protein(s) between the nuclear surface and the kinetochores under cell cycle control. So far, such processes have not been described in higher plant cells. These observations shed light on the putative activity of the plant kinetochore as a protein transporter.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolated Plant Nuclei Nucleate Microtubule Assembly: The Nuclear Surface in Higher Plants Has Centrosome-like Activity

In most eukaryotic cells, microtubules (MTs) are assembled at identified nucleating sites, such as centrosomes or spindle pole bodies. Higher plant cells do not possess such centrosome-like structures. Thus, the fundamental issues of where and how the intracellular plant MTs are nucleated remain highly debatable. A large body of evidence indicates that plant MTs emerge from the nuclear periphery. In this study, we developed an in vitro assay in which isolated maize nuclei nucleate MT assembly at a tubulin concentration (14 [mu]M of neurotubulin) that is not efficient for spontaneous MT assembly. No MT-stabilizing agents, such as taxol or dimethyl sulfoxide, were used. Our model provides evidence that the nuclear surface functions as a MT-nucleating site in higher plant cells. A monoclonal antibody raised against a pericentriolar antigen immunostained the surface of isolated nuclei, and a 100-kD polypeptide in 4 M urea-treated nuclear extracts was detected.

Characterization of a 100-kDa heat-stable microtubule-associated protein from higher plants

In higher-plant cells, the different cell-cycle-dependent microtubule arrays are involved in a wide range of activities including chromosome segregation, cell-plate formation and cellulose microfibril distribution and orientation. A wealth of data, obtained using animal cells, has indicated that the differential stability and function of microtubules during cell-cycle and/or differentiation could be primarily regulated by selective microtubule-associated proteins (MAP). Compared to animal MAP, our knowledge of plant MAP is so far very limited. In this study, we have identified a maize heat-stable protein with apparent molecular mass 100 kDa (P-100) which binds to taxol-stabilized neurotubules and copolymerizes in vitro with purified neural tubulin. Moreover, P-100 cross-reacts with affinity-purified tau antibodies like a maize 83-kDa putative MAP described previously [Vantard, M., Schellenbaum, P., Fellous, A. & Lambert, A. M. (1991) Biochemistry 30, 9334-9340]. Polyclonal antibodies directed against P-100 were obtained and indicated that this protein is found in diverse higher-plant cultured cells suggesting the ubiquitous nature of this protein. P-100 can be phosphorylated in vitro by protein kinases present in a maize cytosol extract. Together, our data suggest that P-100 could be a higher plant MAP.

Microtubule-organizing centers in higher plants

Compelling evidence has recently been obtained for the idea that the nuclear surface of higher plant cells has a microtubule-nucleating function under cell cycle dependent control. Whatever the final organization of microtubules, they all seem to originate in the nuclear periphery. The spatial distribution of microtubules is a secondary process involving actin and microtubule-associated proteins, and other morphogenetic controls. How microtubules are nucleated and/or reorganized at the spindle poles during mitosis remains unknown.

Higher plant microtubule-associated proteins: in vitro functional assays

Microtubule-associated proteins (MAPs) can account for the assembly and stabilization of microtubules at low tubulin concentration, for their ability to interact with other microtubules and/or cytoskeletal polymers or organelles and also for regulating microtubule anchoring and bundling properties. The data concerning higher plant MAPs remain limited so far to a few examples. Motor MAPs such as dynein or kinesin remain poorly documented in plants and are not to be discussed here. In this manuscript, the attention is focused on structural MAPs which co-assemble with tubulin during microtubule assembly. Using taxol, we developed an assay where higher plant microtubules were induced to self-assemble in a cytosolic extract of maize cultured cells and could be used as a native matrix for the isolation of putative higher plant MAPs. Seven polypeptides with molecular masses ranging between 60-125 kDa were found in this MAP-enriched fraction. These putative plant MAPs were shown to co-assemble with pig brain tubulin through two cycles of temperature-dependent assembly-disassembly. They were able to initiate and promote MAP-free tubulin assembly under conditions of non-efficient self-assembly and induced bundling of both plant and neural microtubules. One of these polypeptides (83 kDa) was found to be immunologically related to neural tau, suggesting the presence of common epitopes between neural and plant MAPs. Such epitopes may be present at the microtubule-binding domains, as the higher plant MAPs co-assemble with brain tubulin. Plant microtubules exhibit an important in situ bundling activity, as in cortical or pre-prophase band arrays, or during the drastic reorganization of the cytoskeleton during mitosis induction.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of cholesterol derivatives on cytoskeletal organization of human carcinoma cells

Recent developments of immunotherapeutic approaches have shown that artificial ordering of tumor cell membranes with cholesterol hemisuccinate (CHS) or 25-hydroxycholesterol (25-OH) may significantly enhance the immunogenicity of human renal adenocarcinoma cells. To gain further insight into the molecular mechanism of these sterols, we investigated cytoskeletal modification, which is related to the cell membrane. After treatment of human renal carcinoma cells with these cholesterol (at 10(-6) and 10(-7) M) for 5 days, we observed a disorganization of the submembrane end of the cytoplasmic actin stress fibers by cytofluorescence. The microtubule network was not affected. Thus, in the present study, we found that changes in membrane physicochemical properties impaired the anchorage of actin microfilaments in the plasma membrane of human renal cancer cells. Under the same experimental conditions, such modifications were not observed in normal cells (human fibroblasts) or in human hepatoma cells. We suggest that incubation of cancer cells with these sterols induced a redistribution of the cholesterol-rich membrane microdomains which are linked to the cytoskeleton through submembrane proteins.

A monoclonal antibody, raised against mammalian centrosomes and screened by recognition of plant microtubule organizing centers, identifies a pericentriolar component in different cell types

We have used monoclonal antibodies raised against isolated native calf thymus centrosomes to probe the structure and composition of the pericentriolar material. To distinguish prospective antibodies as specific to conserved elements of this material, we screened clones by their identification of microtubule organizing centers (MTOCs) in different animal and plant cells. Among the clonal antibodies that reacted with MTOCs in both plant and mammalian cells, we describe one (mAb 6C6) that was found to immunostain centrosomes in a variety of bovine and human cells. In cycling cells this signal persisted through the entire cell cycle. Microscopy showed that the mAb 6C6 antigen was a component of the pericentriolar material and this was confirmed by biochemical analysis of centrosomes. Using immunoblot analysis of protein fractions derived from purified components of centrosomes, we have characterized the mAb 6C6 antigen as a 180 kDa polypeptide. We conclude that we have identified a protein component permanently associated with the pericentriolar material. Surprisingly, monoclonal antibody 6C6 also stained other mitotic organelles in mammalian cells, in a cell-cycle-dependent manner. During prometaphase and metaphase the antibody stained both centrosomes and kinetochores. At the onset of anaphase the kinetochore-specific staining dissociated from chromosomes and was subsequently redistributed onto a newly characterized organelle, the telophase disc while the centrosomal stain remained intact. It is not known if the 180 kDa centrosomal protein itself redistributes during mitosis, or if the pattern observed represents other antigens with shared epitopes. The pericentriolar material is thought to be composed of conserved elements, which appeared very early during the evolution of eukaryotes. Our results strongly suggest that mAb 6C6 identifies one of these elements.

Characterization of maize microtubule-associated proteins, one of which is immunologically related to tau

Microtubule-associated proteins (MAPs) are identified as proteins that copurify with tubulin, promote tubulin assembly, and bind to microtubules in vitro. Higher plant MAPs remain mostly unknown. One example of non-tubulin carrot proteins, which bind to neural microtubules and induce bundling, has been reported so far [Cyr, R. J., & Palewitz, B. A. (1989) Planta 177, 245-260]. Using taxol, we developed an assay where higher plant microtubules were induced to self-assemble in cytosolic extracts of maize cultured cells and were used as the native matrix to isolate putative plant MAPs. Several polypeptides with an apparent molecular masses between 170 and 32 kDa copolymerized with maize microtubules. These putative maize MAPs also coassembled with pig brain tubulin through two cycles of temperature-dependent assembly-disassembly. They were able to initiate and promote MAP-free tubulin assembly under conditions of nonefficient self-assembly and induced bundling of both plant and neural microtubules. One of these proteins, of about 83 kDa, cross-reacted with affinity-purified antibodies against rat brain tau proteins, suggesting the presence of common epitope(s) between neural tau and maize proteins. This homology might concern the tubulin-binding domain, as plant and neural tubulins are highly conserved and the plant polypeptides coassembled with brain tubulin.

Incorporation of Paramecium axonemal tubulin into higher plant cells reveals functional sites of microtubule assembly

Incorporation of Paramecium axonemal tubulin into lysed endosperm cells of the higher plant Haemanthus enabled us to identify sites of microtubule assembly. This exogenous Paramecium tubulin could be traced by specific antibodies that do not stain endogenous plant microtubules. Intracellular copolymerization of protozoan and higher plant tubulins gave rise to hybrid polymers that were visualized by immunofluorescence and by immunoelectron microscopy. The addition of exogenous tubulin revealed many free ends of endogenous microtubules that were competent to assemble ciliate tubulin. The functional roles of the nuclear surface and the equatorial region of the phragmoplast as plant microtubule-organizing centers, which were revealed by the intense incorporation of exogenous tubulin, are discussed. These data shed light on the present debate on higher plant microtubule organizing centers.

Microinjected fluorescent phalloidin in vivo reveals the F-actin dynamics and assembly in higher plant mitotic cells

Endosperm mitotic cells microinjected with fluorescent phalloidin enabled us to follow the in vivo dynamics of the F-actin cytoskeleton. The fluorescent probe immediately bound to plant microfilaments. First, we investigated the active rearrangement of F-actin during chromosome migration, which appeared to be slowed down in the presence of phalloidin. These findings were compared with the actin patterns observed in mitotic cells fixed at different stages. Our second aim was to determine the origin of the actin filaments that appear at the equator during anaphase-telophase transition. It is not clear whether this F-actin is newly assembled at the end of mitosis and could control plant cytokinesis or whether it corresponds to a passive redistribution of broken polymers in response to microtubule dynamics. We microinjected the same cells twice, first in metaphase with rhodamine-phalloidin and then in late anaphase with fluorescein isothiocyanate-phalloidin. This technique enabled us to visualize two F-actin populations that are not co-localized, suggesting that actin is newly assembled during cell plate development. These in vivo data shed new light on the role of actin in plant mitosis and cytokinesis.

Amino acid composition and proteolytic generated domains of higher plant tubulin

The molecular architecture of tubulin from higher plant remains unknown. In this report we have made an attempt to identify higher plant tubulin domains using total and limited proteolysis of Haemanthus endosperm tubulin. The tubulin was previously purified and characterized (Picquot and Lambert 1988). The amino acid composition revealed a high content of basic residues, such as arginine and lysine. Tubulin domains were probed by tryptic and chymotryptic cleavage and analyzed by immunoblotting using specific monoclonal antibodies against alpha or beta subunits. These data shed light on specific properties of the higher plant tubulin.

Plant actin filament and microtubule interactions during anaphase--telophase transition: effects of antagonist drugs

F-actin and microtubule co-distribution and interaction were studied during anaphase-telophase. Rapid and drastic changes in the cytoskeleton during these particular stages were studied in isolated plant endosperm cells of the blood lily. These wall-free cells can be considered as natural dividing protoplasts. As identified previously, an F-actin cytoskeletal network characterized the plant cortex and formed an elastic cage around the spindle, remaining throughout interphase, mitosis and cytokinesis. Actin was specifically labeled by fluorescent phalloidin and/or monoclonal antibodies. Gold-labelled secondary antibodies were used for ultrastructural observations and silver-enhancement was applied for video-enhanced microscopy. Microtubule and microfilament dynamics and interaction were studied using drug antagonists to actin (cytochalasins B, D) and to tubulin (colchicine). This permitted precise correlations to be made between chromosome movement inhibition and alteration in the actin/tubulin cytoskeleton. During anaphase chromosome migration, the cortical actin network was stretched along the microtubular spindle, while it remained homogeneous when anaphase was inhibited by colchicine. Cytochalasins did not inhibit chromosome movement but altered actin distribution. A new population of actin filaments appeared at the equator in late anaphase before the microtubular phragmoplast was formed and contributed to cell plate formation. Our conclusion is that F-actin-microtubule interaction may contribute to the regulatory mechanism of plant cytokinesis.

Characterization and dynamics of cytoplasmic F-actin in higher plant endosperm cells during interphase, mitosis, and cytokinesis

We have identified an F-actin cytoskeletal network that remains throughout interphase, mitosis, and cytokinesis of higher plant endosperm cells. Fluorescent labeling was obtained using actin monoclonal antibodies and/or rhodamine-phalloidin. Video-enhanced microscopy and ultrastructural observations of immunogold-labeled preparations illustrated microfilament-microtubule co-distribution and interactions. Actin was also identified in cell crude extract with Western blotting. During interphase, microfilament and microtubule arrays formed two distinct networks that intermingled. At the onset of mitosis, when microtubules rearranged into the mitotic spindle, microfilaments were redistributed to the cell cortex, while few microfilaments remained in the spindle. During mitosis, the cortical actin network remained as an elastic cage around the mitotic apparatus and was stretched parallel to the spindle axis during poleward movement of chromosomes. This suggested the presence of dynamic cross-links that rearrange when they are submitted to slow and regular mitotic forces. At the poles, the regular network is maintained. After midanaphase, new, short microfilaments invaded the equator when interzonal vesicles were transported along the phragmoplast microtubules. Colchicine did not affect actin distribution, and cytochalasin B or D did not inhibit chromosome transport. Our data on endosperm cells suggested that plant cytoplasmic actin has an important role in the cell cortex integrity and in the structural dynamics of the poorly understood cytoplasm-mitotic spindle interface. F-actin may contribute to the regulatory mechanisms of microtubule-dependent or guided transport of vesicles during mitosis and cytokinesis in higher plant cells.

The life-span trend in the magnitude of the Mueller-Lyer illusion as a function of hue and age

Mueller-Lyer illustrations produced by hue contrast were used to investigate age differences with participants ranging in age from 20 to 79 years. As expected, there was no age difference in the magnitude of the illusion when the Mueller-Lyer figure was produced by hue contrast. A significant main effect of hue was found, with no interaction between hue and age. These findings support Pollack's nondevelopmental explanation for age effects on Type I illusions.

Characterization and immunocytochemical distribution of calmodulin in higher plant endosperm cells: localization in the mitotic apparatus

In this study we have examined the immunocytochemical distribution of calmodulin during mitosis of higher plant endosperm cells. Spindle development in these cells occurs without centrioles. Instead, asterlike microtubule converging centers appear to be involved in establishing spindle polarity. By indirect immunofluorescence and immunogold staining methods with anti-calmodulin antibodies, we found endosperm calmodulin to be associated with the mitotic apparatus, particularly with asterlike and/or polar microtubule converging centers and kinetochore microtubules, in an immunocytochemical pattern distinct from that of tubulin. In addition, endosperm calmodulin and calcium showed analogous distribution profiles during mitosis. Previous reports have demonstrated that calmodulin is associated with the mitotic apparatus in animal cells. The present observation that calmodulin is also associated with the mitotic apparatus in acentriolar, higher plant endosperm cells suggests that some of the regulatory mechanisms involved in spindle formation, microtubule disassembly, and chromosome movement in plant cells may be similar to those in animal cells. However, unlike animal cell calmodulin, endosperm calmodulin appears to associate with kinetochore microtubules throughout mitosis, which suggests a specialized role for higher plant calmodulin in the regulation of kinetochore microtubule dynamics.

Effect of renal function and dialysis on temocillin pharmacokinetics

Temocillin pharmacokinetics in renal impairment were investigated following an intravenous bolus injection of 15 mg/kg. The 28 patients were divided into 5 groups of varying renal function, from normal to uraemic [including a group being treated with haemodialysis and a group on continuous ambulatory peritoneal dialysis (CAPD)]. The distribution of temocillin into the tissues was not affected by renal dysfunction. Uraemia as compared to normal renal function resulted in a 4.3-fold decrease in temocillin clearance and a 3.1-fold decrease in urinary recovery over 24 hours, as well as a 5- and 3.7-fold increase in the beta half-life and the area under the curve (AUC), respectively. Haemodialysis doubled the serum clearance and halved the beta half-life of temocillin in the uraemic subject, but CAPD over 24 hours eliminated only 8% of the temocillin dose, resulting in a minimal change in pharmacokinetics. Temocillin dosage adjustments in renal failure are proposed.

Aster-like microtubule centers establish spindle polarity during interphase - Mitosis transition in higher plant cells

Transformation of interphase microtubular cytoskeleton into initial mitotic spindle in early prophase and the reverse process in telophase were analysed with immunofluorescence techniques in endosperm cells of higher plants, Haemanthus Katherinae Bak. and Clivia nobilis Lindl. We have identified aster-like centers as intermediate basic microtubular structures directly involved in the reorganization of microtubules arrays both at the onset of mitosis and during telophase-interphase transition. These transitory microtubule converging centers determine spindle polarity in early prophase, they are replaced by diffuse poles during metaphase, and form again in anaphasetelophase. We conclude that rearrangement of microtubules during interphase-mitosis involves three superimposed processes: microtubule assembly/disassembly, active transport and reorientation of microtubules, changes in microtubule properties reflected in their lateral interaction during spindle development.

The pharmacokinetics of temocillin in patients with normal and impaired renal function

The pharmacokinetics of temocillin was studied in 16 subjects with varying degrees of renal functional impairment. The subjects were divided into three groups, depending on their creatinine clearance: Group A greater than 70 ml/min/1.73 m2; Group B 20-70ml/min/1.73 m2 and Group C less than 20 ml/min/1.72 m2. Following intravenous administration the total serum clearance of temocillin was reduced in patients with renal insufficiency. The distribution of temocillin into the tissues was not affected by renal dysfunction, apparent distribution volumes being 15.11, 16.01 and 13.81 in Groups A, B and C respectively. The change in clearance was reflected in an increased area under the serum concentration versus time curve from 418 mg h/l in Group A to 1301 mg h/l and 1553 mg h/l in Groups B and C respectively. The beta elimination half-life was also prolonged from 3.5 h in Group A 12.7 h in Group B and 17.5 h in Group C. The urinary excretion of temocillin was both delayed and reduced according to the extent of kidney damage. The reduction in temocillin clearance was proportional to the extent of reduction from normal of the clearance of creatinine. This relationship has been used to suggest dosage schedules for temocillin in patients with renal insufficiency.

The in vitro activity of ceftazidime against resistant clinical isolates

The in vitro activity of ceftazidime was determined using an agar dilution technique and compared with that of cefotaxime and moxalactam against 559 clinically important isolates. Ceftazidime showed poor activity against Bacteroides and Campylobacter, moderate activity against Staphylococcus aureus and excellent activity against Haemophilus, Aeromonas and the Enterobacteriaceae. 91% of 324 cephalothin-resistant Enterobacteriaceae were inhibited at a concentration of 1 mg/l. Ceftazidime was the most active drug against Acinetobacter. It also showed exceptional activity against Pseudomonas, inhibiting 90% of the strains at a concentration of 4 mg/l. A significant inoculum effect was only seen with inocula of 10(6) cfu or higher, and depended on the strain tested and the methodology employed.

Visualization of microtubules in interphase and mitotic plant cells of Haemanthus endosperm with the immuno-gold staining method

A procedure is presented for the immunocytochemical visualization of microtubules in interphase and mitotic cells of Haemanthus endosperm. It includes preservation of microtubules (MTs) with glutaraldehyde and uses colloidal gold, coated with secondary antibodies, in a novel indirect-light microscopic technique: the immuno-gold staining method. This immunocytochemical stain allows us to follow the changes in distribution of MTs during mitosis with greater precision and specificity than allowed by other light microscopic techniques. Many aspects of MT arrangements, as reported from ultrastructural studies, are corroborated and extended. This demonstrates the reliability of the technique. In addition, a number of significant observations were made. These concern (i) the presence of a network of MTs in interphase cells, (ii) the transformation of this network into a spindle-like cage of MTs (the clear zone) surrounding the nucleus during prophase, (iii) the drastic rearrangement of MT distribution during prometaphase, (iv) new evidence for the formation of aster-like arrays of polar MTs during anaphase, and (v) the development of the phragmoplast.

Diamètre intrinsèque d'une fibre non gainée de forme quelconque: définition et détermination numérique

In this paper, the intrinsic diameter of the noncircular cross section of an unclad optical fiber is defined and determines the fiber dimension. Its value can be determined by studying the forwardscattering pattern from the fiber illuminated by a laser beam perpendicular to its axis. A knowledge of the shape of the fiber is not necessary. The suggested method is nondestructive. Moreover, it provides an estimate of the deformation of the fiber cross section.

Détermination de défauts de circularité de la section d'une fibre optique non gainée

Study of the light scattered from an unclad optical fiber illuminated by a laser beam perpendicular to its axis gives a valuation of little defects of the fiber cross section. The shifts of some bright fringes that occur when the fiber is rotated are observed. Comparison between experimental measurements and ray interference computations shows that the cross section of the fiber under test is neither circular nor elliptical, but can be described with good approximation by a limited Fourier series, the coefficients of which are estimated.

A prospective community survey for aminoacidaemias

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Dietary treatment of homocystinuria

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