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PubMed1985

Limits of neurogenesis in primates.

Systematic analysis of autoradiograms prepared from postpubertal rhesus monkeys given single and multiple injections of tritium-labeled thymidine and killed 3 days to 6 years later displayed a slow turnover of glial cells but failed to reveal any radiolabeled neurons. Therefore, unlike neurons of some nonprimate species, all neurons of the rhesus monkey brain are generated during prenatal and early postnatal life. A stable population of neurons in primates, including humans, may be important for the continuity of learning and memory over a lifetime.

Amphibians↗

PubMed1976

Effect of dissolved oxygen and Eh and Bacteroides fragilis during continuous culture.

Bacteroides fragilis subsp. fragilis was maintained in a chemostat modified for anaerobic conditions to test the effects of dissolved oxygen and Eh on growth. Using a defined medium containing glucose and a dilution rate of 0.16 h -1, a stable population of 3 X 10(9) colony-forming units/ml was present. At this steady state, the pH was 5.6, the Eh was -50 mV, and the dissolved oxygen concentration was 0% atmospheric saturation. The Eh was then adjusted to +300 mV by adding potassium ferricyanide while oxygen was excluded; in this system there were no demonstrable changes from the steady state in viable cells, pH, glucose concentration, or volatile fatty acid production. In other experiments oxygen was introduced into the original steady state at a dissolved oxygen concentration of 10% atmospheric saturation for a period of 6 to 8 h. During O2 exposure, the viable cell count decreased at a rate comparable to the theoretical washout rate for a static bacterial culture. Similar results were obtained with a dissolved oxygen concentration of 25 and 100%. Other effects of O2 exposure included an increase in Eh from -50 to +250 mV, a decrease in glucose consumption, and a decrease in volatile fatty acid production. These results suggest that dissolved oxygen has a bacteriostatic effect on B. fragilis in continuous culture, which may be independent of changes in Eh alone.

Acetates↗

PubMed1990

Effect of aerosolization on subsequent bacterial survival.

To determine whether aerosolization could impair bacterial survival, Pseudomonas syringae and Erwinia herbicola were aerosolized in a greenhouse, the aerosol was sampled at various distances from the site of release by using all-glass impingers, and bacterial survival was followed in the impingers for 6 h. Bacterial survival subsequent to aerosolization of P. syringae and E. herbicola was not impaired 1 m from the site of release. P. syringae aerosolized at 3 to 15 m from the site of release at a temperature of 12 degrees C and a relative humidity of 80% survived 35- to 65-fold better than P. syringae released at 27 degrees C and a relative humidity of 40%. No difference was observed in the survival of P. syringae and E. herbicola following aerosolization at the same temperature and relative humidity. Bacteria sprayed directly onto bean and oat plants established stable populations at comparable numbers on both plants over an 8-day period following inoculation. Bacteria that inoculated adjacent plants by drifting downwind up to 5 m were detectable at an initial population of 10(2) CFU/g on oats and 10(5) CFU/g on beans 2 h after the spray. However, bacterial populations on both plants were undetectable within 48 h.

Aerosols↗

PubMed1992

Expression and transfer of engineered catabolic pathways harbored by Pseudomonas spp. introduced into activated sludge microcosms.

Two genetically engineered microorganisms (GEMs), Pseudomonas sp. strain B13 FR1(pFRC20P) (FR120) and Pseudomonas putida KT2440(pWWO-EB62) (EB62), were introduced into activated sludge microcosms that had the level of aeration, nutrient makeup, and microbial community structure of activated sludge reactors. FR120 contains an experimentally assembled ortho cleavage route for simultaneous degradation of 3-chlorobenzoate (3CB) and 4-methyl benzoate (4MB); EB62 contains a derivative TOL plasmid-encoded degradative pathway for toluene experimentally evolved so that it additionally processes 4-ethyl benzoate (4EB). Experiments assessed survival of the GEMs, their ability to degrade target substrates, and lateral transfer of plasmid-encoded recombinant DNA. GEMs added at initial densities of 10(6) to 10(7) bacteria per ml of activated sludge declined to stable population densities of 10(4) to 10(5) bacteria per ml. FR120 degraded combinations of 3CB and 4MB (1 mM each) following 3 days of adaptation in the microcosms. Indigenous microorganisms required an 8-day adaptation period before degradation of 4MB was observed; 3CB was degraded only after the concentration of 4MB was much reduced. The indigenous microbial community was killed when both compounds were present at concentrations of 4.0 mM. However, in parallel microcosms containing FR120, the microbial community maintained a normal density of viable cells. Indigenous microbes readily degraded 4EB (2 mM), and EB62 did not significantly increase the observed rate of degradation. In filter matings, transfer of pFRC20P, which specifies mobilization but not transfer functions, from FR120 to P. putida UWC1 was not detectable (< 10(-7) transconjugants per donor cell).(ABSTRACT TRUNCATED AT 250 WORDS)

Benzoates↗

PubMed1997

Degradation of Chlorophenols by Alcaligenes eutrophus JMP134(pJP4) in Bleached Kraft Mill Effluent.

The ability of Alcaligenes eutrophus JMP134(pJP4) to degrade 2,4-dichlorophenoxyacetic acid, 2,4,6-trichlorophenol, and other chlorophenols in a bleached kraft mill effluent was studied. The efficiency of degradation and the survival of strain JMP134 and indigenous microorganisms in short-term batch or long-term semicontinuous incubations performed in microcosms were assessed. After 6 days of incubation, 2,4-dichlorophenoxyacetate (400 ppm) or 2,4,6-trichlorophenol (40 to 100 ppm) were extensively degraded (70 to 100%). In short-term batch incubations, indigenous microorganisms were unable to degrade such of compounds. Degradation of 2,4,6-trichlorophenol by strain JMP134 was significantly lower at 200 to 400 ppm of compound. This strain was also able to degrade 2,4-dichlorophenoxyacetate, 2,4,6-trichlorophenol, 4-chlorophenol, and 2,4,5-trichlorophenol when bleached Kraft mill effluent was amended with mixtures of these compounds. On the other hand, the chlorophenol concentration and the indigenous microorganisms inhibited the growth and survival of the strain in short-term incubations. In long-term (>1-month) incubations, strain JMP134 was unable to maintain a large, stable population, although extensive 2,4,6-trichlorophenol degradation was still observed. The latter is probably due to acclimation of the indigenous microorganisms to degrade 2,4,6-trichlorophenol. Acclimation was observed only in long-term, semicontinuous microcosms.

Journal Article↗

PubMed1998

Microcosm enrichment of biphenyl-degrading microbial communities from soils and sediments.

A microcosm enrichment approach was employed to isolate bacteria which are representative of long-term biphenyl-adapted microbial communities. Growth of microorganisms was stimulated by incubating soil and sediment samples from polluted and nonpolluted sites with biphenyl crystals. After 6 months, stable population densities between 8 x 10(9) and 2 x 10(11) CFU/ml were established in the microcosms, and a large percentage of the organisms were able to grow on biphenyl-containing minimal medium plates. A total of 177 biphenyl-degrading strains were subsequently isolated and characterized by their ability to grow on biphenyl in liquid culture and to accumulate a yellow meta cleavage product when they were sprayed with dihydroxybiphenyl. Isolates were identified by using a polyphasic approach, including fatty acid methyl ester (FAME) analysis, 16S rRNA gene sequence comparison, sodium dodecyl sulfate-polyacrylamide gel electrophoresis of whole-cell proteins, and genomic fingerprinting based on sequence variability in the 16S-23S ribosomal DNA intergenic spacer region. In all of the microcosms, isolates identified as Rhodococcus opacus dominated the cultivable microbial community, comprising a cluster of 137 isolates with very similar FAME profiles (Euclidean distances, <10) and identical 16S rRNA gene sequences. The R. opacus isolates from the different microcosms studied could not be distinguished from each other by any of the fingerprint methods used. In addition, three other FAME clusters were found in one or two of the microcosms analyzed; these clusters could be assigned to Alcaligenes sp., Terrabacter sp., and Bacillus thuringiensis on the basis of their FAME profiles and/or comparisons of the 16S rRNA gene sequences of representatives. Thus, the microcosm enrichments were strongly dominated by gram-positive bacteria, especially the species R. opacus, independent of the pollution history of the original sample. R. opacus, therefore, is a promising candidate for development of effective long-term inocula for polychlorinated biphenyl bioremediation.

Bacterial Typing Techniques↗

PubMed2005

Physiology and phylogeny of green sulfur bacteria forming a monospecific phototrophic assemblage at a depth of 100 meters in the Black Sea.

The biomass, phylogenetic composition, and photoautotrophic metabolism of green sulfur bacteria in the Black Sea was assessed in situ and in laboratory enrichments. In the center of the western basin, bacteriochlorophyll e (BChl e) was detected between depths of 90 and 120 m and reached maxima of 54 and 68 ng liter(-1). High-pressure liquid chromatography analysis revealed a dominance of farnesyl esters and the presence of four unusual geranyl ester homologs of BChl e. Only traces of BChl e (8 ng liter(-1)) were found at the northwestern slope of the Black Sea basin, where the chemocline was positioned at a significantly greater depth of 140 m. Stable carbon isotope fractionation values of farnesol indicated an autotrophic growth mode of the green sulfur bacteria. For the first time, light intensities in the Black Sea chemocline were determined employing an integrating quantum meter, which yielded maximum values between 0.0022 and 0.00075 micromol quanta m(-2) s(-1) at the top of the green sulfur bacterial layer around solar noon in December. These values represent by far the lowest values reported for any habitat of photosynthetic organisms. Only one 16S rRNA gene sequence type was detected in the chemocline using PCR primers specific for green sulfur bacteria. This previously unknown phylotype groups with the marine cluster of the Chlorobiaceae and was successfully enriched in a mineral medium containing sulfide, dithionite, and freshly prepared yeast extract. Under precisely controlled laboratory conditions, the enriched green sulfur bacterium proved to be capable of exploiting light intensities as low as 0.015 micromol quanta m(-2) s(-1) for photosynthetic 14CO2 fixation. Calculated in situ doubling times of the green sulfur bacterium range between 3.1 and 26 years depending on the season, and anoxygenic photosynthesis contributes only 0.002 to 0.01% to total sulfide oxidation in the chemocline. The stable population of green sulfur bacteria in the Black Sea chemocline thus represents the most extremely low-light-adapted and slowest-growing type of phototroph known to date.

Chlorobi↗

PubMed1981

Effect of long generation times on growth of Bacteroides thetaiotaomicron in carbohydrate-induced continuous culture.

We investigated the ability of Bacteroides thetaiotaomicron, an obligate anaerobe from human colonic microflora, to grow in a carbohydrate-limited continuous culture at generation times ranging from 3.5 to 28 h per division. Four carbohydrates were tested: glucose, N-acetylglucosamine, glucuronic acid, and glucosamine. At a generation time of 3.5 h per division, the growth yields for bacteria growing on glucose, N-acetylglucosamine, and glucuronic acid were 76, 68, and 50 g of cells (dry weight) per mol of substrate, respectively. Growth yields at 28 h per division were 61, 52, and 37 g/mol of substrate, respectively. When glucosamine was the carbohydrate source, a stable population of bacteria was attainable only at generation times longer than 12 h per division. Growth yields at 15 and 32 h per division were 11 and 33 g/mol of substrate, respectively. There was no significant variation with increasing generation times in the specific activities of selected glycolytic enzymes, of disaccharidases such as alpha- and beta-glucosidases and alpha- and beta-galactosidases, or of the polysaccharidase chondroitin sulfate lyase. By contrast, the pattern of fermentation products varied with both the generation time and the carbon source. At a generation time of 3.5 h per division, the main products from the fermentation of glucose were acetate and succinate, with a trace of propionate. At 28 h per division, propionate concentrations were higher and succinate concentrations were lower than at 3.5 h per division. The products from the fermentation of glucosamine were the same as those from glucose fermentation. However, when N-acetylglucosamine was fermented, the concentration of acetate was much higher at all generation times than when glucose was the carbon source. When glucuronic acid was the carbon source, acetate was the main fermentation product, and only traces of propionate and succinate were detected. Another characteristic that varied with the growth rate was the ability of B. thetaiotaomicron to produce the inducible enzyme alpha-glucosidase when exposed to maltose. The ability of the organism to produce this enzyme declined with increasing generation times.

Acetylglucosamine↗

PubMed1980

Establishment and maintenance of persistent infection by Sindbis virus in BHK cells.

We have established a persistent infection of BHK cells with a preparation of Sindbis virus heavily enriched in defective interfering (DI) particles. The small fraction of cells that survived the initial infection grew out to form a stable population of cells [BHK(Sin-1) cells], most of which synthesized viral RNA and viral antigens. The presence of DI particles in this virus stock was required to establish this persistent state. BHK(Sin-1) cells released a small-plaque, temperature-sensitive virus (Sin-1 virus) as well as DI particles containing DI RNAs larger than those present in the original stock used to establish the persistent state. A cloned stock of Sin-1 virus, free of detectable DI particles, was able to initiate a persistent infection more quickly and with greater cell survival than the original stock of Sindbis virus containing DI particles. About 2 weeks after the Sin-1 virus-infected cells were cultured, DI RNAs arose and soon became the dominant viral RNA species produced by these cells.

Animals↗

PubMed1989

Variability and evolution of the plant RNA virus pepper mild mottle virus.

The RNA genomes of 26 isolates of pepper mild mottle virus were compared by their RNase T1 fingerprints. Twenty-three isolates came from epidemic outbreaks in greenhouse-grown peppers in Almería (southeastern Spain) from 1983 to 1987; three other isolates, from 1980, came from Sicily (Italy) and Zaragoza (central Spain). The 26 fingerprints can be classified into 10 different types; nucleotide substitution rates show them to be very similar. Cluster and cladistic analyses group types corresponding to the Almería isolates separate from those of 1980. Intraannual and interannual nucleotide differences were estimated. An evolutionary model for pepper mild mottle virus built on these data indicates a highly stable population, maintaining its diversity through time, with a main prevailing haplotype from which closely related variants arise that do not replace it. This high stability could be due to strong functional constraints on variation, as suggested by the high proportion of invariant versus polymorphic sites in fingerprints.

Biological Evolution↗

PubMed1996

Herpes simplex virus type 1 protein IE63 affects the nuclear export of virus intron-containing transcripts.

Using in situ hybridization labelling methods, we have determined that the herpes simplex virus type 1 immediate-early protein IE63 (ICP27) affects the cellular localization of virus transcripts. Intronless transcripts from the IE63, UL38, and UL44 genes are rapidly exported to and accumulate in the cytoplasm throughout infection, in either the presence or absence of IE63 expression. The intron-containing transcripts from the IE110 and UL15 genes, while initially cytoplasmic, are increasingly retained in the nucleus in distinct clumps as infection proceeds, and the clumps colocalize with the redistributed small nuclear ribonucleoprotein particles. Infections with the IE63 mutant virus 27-lacZ demonstrated that in the absence of IE63 expression, nuclear retention of intron-containing transcripts was lost. The nuclear retention of UL15 transcripts, which demonstrated both nuclear and cytoplasmic label, was not as pronounced as that of the IE110 transcripts, and we propose that this is due to the late expression of UL15. Infections with the mutant virus 110C1, in which both introns of IE110 have been precisely removed (R.D. Everett, J. Gen. Virol. 72:651-659, 1991), demonstrated IE110 transcripts in both the nucleus and the cytoplasm; thus, exon definition sequences which regulate viral RNA transport are present in the IE110 transcript. By in situ hybridization a stable population of polyadenylated RNAs was found to accumulate in the nucleus in spots, most of which were separate from the small nuclear ribonucleoprotein particle clumps. The IE63 protein has an involvement, either direct or indirect, in the regulation of nucleocytoplasmic transport of viral transcripts, a function which contrasts with the recently proposed role of herpes simplex virus type 1 Us11 in promoting the nuclear export of partially spliced or unspliced transcripts (J.-J. Diaz, M. Duc Dodon, N. Schaerer-Uthurraly, D. Simonin, K. Kindbeiter, L. Gazzolo, and J.-J. Madjar, Nature [London] 379:273-277, 1996), the significance of which is discussed.

Biological Transport↗

PubMed1991

Multilevel assessment of immunisation uptake as a performance measure in general practice.

OBJECTIVE: To provide a measure of general practitioners' performance regarding uptake of immunisation against pertussis, taking account of the impact of patient characteristics on levels of uptake. DESIGN: Multilevel model of immunisation status against six measures of patient characteristics (level 1 predictor variables) with practice constraints as level 2 variables. SETTING: 126 practices in southern England. SUBJECTS: 2048 infants identified from infant surveillance and immunisation records. MAIN OUTCOME MEASURES: Top 10 practices with respect to uptake of pertussis immunisation according to a "null" model (model A) and according to a model that included six level 1 variables (model B); differences in ranking between the two models. RESULTS: Practices with low numbers of infants' requiring immunisation had imprecise and unstable uptake rates (range 0%-100%). With the multilevel procedure, after controlling for patient characteristics, practices in suburban catchment areas comprised largely of mature or young professionals performed best. Most improved performances when patient characteristics were taken into account were in practices in areas with a stable population and local authority housing--one such practice improved its ranking by 47 places. CONCLUSIONS: Crude uptake rates are inadequate performance indicators. Alternative approaches suggest that praiseworthy efforts to raise immunisation rates in unpromising areas are unrewarded by simple target based assessments.

Achievement↗

PubMed1992

Longitudinal study of gall stone prevalence at necropsy.

A prospective study of the prevalence of gall stone disease at necropsy in a stable population has been undertaken over a 10 year period up to June 1988. In women, the prevalence of gall stone disease remained static but in men aged 50-59 years it rose from 7% (n = 148) in the first three years to 18% (n = 138) in the last three years (p less than 0.01) and in men aged 60-69 it rose from 12% (n = 370) to 20% (n = 366, p less than 0.01). In the latter age group the female: male ratio fell from 2:1 to 0.8:1. The proportion of deaths from coronary heart disease in men fell slightly in those over 70 during the study period. There was a fall in deaths from coronary heart disease in all age groups in women. Men with gall stones were less likely to have had a cholecystectomy than women, and overall 88% of gall stones remained in situ. In a parallel clinical study, the number of cholecystectomies carried out in the same district fell by 18% over the 10 years without any apparent change in the provision of resources. Cholecystectomy remained almost three times more frequent in women. National data indicate that there have been major changes in the average diet before and during the period of study in favour of reducing coronary heart disease. There has been no change in mortality from coronary heart disease in young men but if the observed increase in the prevalence of gall stones in men and the decrease in deaths from coronary heart disease in women are real phenomena, it seems likely that they are diet related.

Age Factors↗

PubMed2002

Protective effect of faecal occult blood test screening for colorectal cancer: worse prognosis for screening refusers.

BACKGROUND AND AIMS: Screening for colorectal cancer (CRC) by faecal occult blood testing (FOBT) decreases CRC mortality by 15-33%. Compliance remains an obstacle to maximising the benefit of FOBT screening. We tested the hypothesis that individuals offered FOBT screening but refused would have an increased incidence and worse prognosis for CRC compared with those tested and with controls. METHODS: Annual screening was offered to 3548 average risk individuals, > or = 40 years of age, from a highly stable population. A total of 2538 agreed to testing (group 1) and 1010 (28%) refused (group 2). Another 1376 individuals were never offered the test and served as controls (group 3). The groups were followed for 11 years: a three year screening period (1985-1987) and an eight year follow up period at the end of the screening programme (1988-1995). Incidence, stage, and mortality were compared. Characterisation of refusers was completed in 188 and 130 subjects of groups 1 and 2, respectively. RESULTS: In the screening phase, mortality from CRC was significantly lower in group 1 than in groups 2 and 3. The cumulative incidence of CRC in the eight year follow up period was 21 (0.88%), 23 (2.28%), and 13 (0.94%) in groups 1, 2, and 3, respectively. This shows a reduction of 61.4% in group 1 compared with group 2 (relative risk 0.28 (95% confidence interval (CI) 0.19-0.32)) (p<0.001) and 6.4% compared with group 3 (relative risk 0.93 (95% CI 0.93-1.00)) (NS). During follow up, group 1 subjects also demonstrated a decrease in advanced Dukes' stage and mortality rate by 80% and 64%, and 79% and 62%, compared with groups 2 and 3, respectively. Refusers were more likely to be male, of Asian-African descent, and more likely to smoke, consume more coffee, and less tea or dairy foods. CONCLUSIONS: When accepted, FOBT may protect against CRC for prolonged periods. Individuals who refuse FOBT have a significantly higher CRC incidence and mortality rates than those who accept testing.

Adult↗

PubMed1971

Quality control in routine haemoglobinometry.

An analysis of haemoglobin estimations in a routine laboratory shows that quality control methods based on mean values are unsatisfactory. The use of a cusum method together with control samples is a sensitive and convenient technique for the early discovery of minor deviations in results and it is not dependent on a stable population of patients.

Hemoglobinometry↗

PubMed1978

Incidence of congestive cardiomyopathy.

In a stable population of 250 000, the diagnosis of congestive cardiomyopathy could be firmly established in fifty-nine cases during a period of 8 years. This gives an incidence of the disease of 3/100 000/year. If cases disclosed at post-mortem during the same period are included, the frequency of the disease will equal 5/100 000/year.

Adolescent↗

PubMed1998

Comparison of the functional results of single lung transplantation for pulmonary fibrosis and chronic airway obstruction.

BACKGROUND: Single lung transplantation (SLT) is now a treatment option for patients with both pulmonary fibrosis and advanced chronic airway obstruction. Lung function after transplantation might be expected to be different in these two groups of patients because of the effect of the remaining native lung, but the implications of these differences have not been fully explored. METHODS: The functional results of a stable population of 20 patients (13 chronic airway obstruction, seven pulmonary fibrosis) after SLT with no evidence of obliterative bronchiolitis were analysed. The differences between the two populations in the interrelations between and determinants of total lung capacity (TLC), subdivisions of lung volume, airway function (spirometry, maximum expiratory flow volume curves, and moments analysis of the spirogram) respiratory mechanics (PV curves and maximal respiratory pressures), CO transfer factor (TLCO) and the distribution of perfusion, ventilation and volume of the transplanted and native lungs were compared. RESULTS: Total lung capacity after SLT (TLCpost) was normal in the patients with pulmonary fibrosis (mean (SE) 103.9 (6.9)% predicted) but remained significantly elevated in patients with airway obstruction (126.4 (4.4)%. Forced expiratory volume in one second (FEV1) and vital capacity (VC) improved to similar values after SLT in both groups with a final VC of 76.8 (5.9)% and 66.7 (3.9)% in patients with fibrosis and airway obstruction, respectively. Maximum expiratory flows were generally lower and moments analysis of the spirogram showed slower lung emptying with significantly greater second and third moments (alpha 2 and alpha 3) in patients with airway obstruction. Relative ventilation and perfusion of the transplanted lung were both greater in both populations but relative ventilation of the transplanted lung was significantly greater in patients treated for airway disease than in those with pulmonary fibrosis. TLCO was also significantly higher in patients who had received a transplant for chronic airway obstruction. CONCLUSIONS: These results suggest that differences in the functional results of SLT for airway disease and pulmonary fibrosis are relatively minor. In this series the native hyperinflated lung in chronic airway disease was not more disadvantageous to overall function than the native lung in pulmonary fibrosis. However, tests of lung function based on the terminal portion of the forced spirogram are likely to be less sensitive for the detection of obliterative bronchiolitis in patients who have received a transplant for advanced airway obstruction than in those with pulmonary fibrosis.

Female↗

PubMed1986

Isolated canine mastocytoma cells: propagation and characterization of two cell lines.

Five different dog mastocytoma tumors were successfully transplanted and propagated in BALB/c nude mice. Cells from two of these tumors were passaged serially through at least four generations of mice without morphological or functional change. The average yield from a 2-cm tumor harvested from a mouse was 1.2 +/- 2.8 X 10(9) mast cells with greater than 90% viability. Cells of one line were larger and more heavily granulated than the other, and contained 1.29 +/- 0.74 pg histamine/cell (mean +/- SD). Calcium ionophore A23187 and compound 48/80 caused dose dependent histamine release with no significant difference in release from generation to generation. The smaller cells contained 0.06 +/- 0.06 pg histamine/cell. Histamine release after calcium ionophore or compound 48/80 was dose dependent and unchanged through serial passages. Following passive sensitization antigen caused dose-dependent histamine release confirming the presence of IgE receptors on these cells. In both cell lines histamine release was inhibited by terbutaline, dibutyryl adenosine 3',5'-cyclic monophosphate, or isobutylmethylxanthine. These methods provide a morphologically and functionally stable population of nearly pure canine mast cells for biochemical and physiological studies.

Animals↗