Administration of Lactobacillus johnsonii FI9785 to chickens affects colonisation by Campylobacter jejuni and the intestinal microbiota

1. Campylobacter jejuni is the most common bacterial cause of human food-borne gastroenteritis in the world. A major source of human infection is the consumption of contaminated meat, particularly poultry. New control measures to reduce or eliminate this pathogen from the animal gastrointestinal tract are urgently required, and the use of probiotics as competitive exclusion agents is a promising biocontrol measure to reduce C. jejuni in the food chain. 2. In this study, we assessed the potential of Lactobacillus johnsonii FI9785, which has shown efficacy against Clostridium perfringens, to combat C. jejuni. The effect of prophylactic administration of L. johnsonii on the ability of C. jejuni to colonise chickens was determined. 3. Two doses of L. johnsonii given a week apart led to a reduction in C. jejuni colonisation in the caecal contents, but this biocontrol seemed reliant upon a high level of initial colonisation by the probiotic. 4. The microbial composition in the chicken gut was significantly altered by the probiotic treatment, as shown by denaturing gradient gel electrophoresis of 16S rRNA gene amplicons. 5. Together these results demonstrate the potential of this probiotic strain to be tested further as a competitive exclusion agent in poultry against C. jejuni.

Metformin and prostate cancer stem cells: a novel therapeutic target

Prostate cancer is the second most frequently diagnosed cancer in the world. Localized disease can be effectively treated with radiation therapy or radical prostatectomy. However, advanced prostate cancer is more difficult to treat and if metastatic, is incurable. There is a need for more effective therapy for advanced prostate cancer. One potential target is the cancer stem cell (CSC). CSCs have been described in several solid tumors, including prostate cancer, and contribute to therapeutic resistance and tumor recurrence. Metformin, a common oral biguanide used to treat type 2 diabetes, has been demonstrated to have anti-neoplastic effects. Specifically, metformin targets CSCs in breast cancer, pancreatic cancer, glioblastoma and colon cancer. Metformin acts directly on the mitochondria to inhibit oxidative phosphorylation and reduce mitochondrial ATP production. This forces tumor cells to compensate by increasing the rate of glycolysis. CSCs rely heavily on mitochondrial oxidative phosphorylation for energy production. The glycolytic switch results in an energy crisis in these cells. Metformin could be used to exploit this metabolic weakness in CSCs. This would increase CSC sensitivity to conventional cancer therapies, circumventing treatment resistance and enhancing treatment efficacy. This review will explore the characteristics of prostate CSCs, their role in tumor propagation and therapeutic resistance and the role of metformin as a potential prostate CSC sensitizer to current anticancer therapies.

Visualization of acoustic cavitation effects on suspended calcite crystals

The acoustic cavitation (42,080 Hz, 7.1 W cm(-2) or 17 W) effects on suspended calcite crystals, sized between 5 and 50 μm, have been visualized for the first time using high speed photography. High speed recordings with a duration of 1 s containing up to 300,000 frames per second, revealed the effect of cluster and streamer cavitation on several calcite crystals. Cavitation clusters, evolved from cavitation inception and collapse, caused attrition, disruption of aggregates and deagglomeration, whereas streamer cavitation was observed to cause deagglomeration only. Cavitation on the surface gave the crystals momentum. However, it is shown that breakage of accelerated crystals by interparticle collisions is unrealistic because of their small sizes and low velocities. Crystals that were accelerated by bubble expansion, subsequently experienced a deceleration much stronger than expected from drag forces, upon bubble collapse. Experiments with pre-dried crystals seemed to support the current theory on bubble nucleation through the presence of pre-existing gas pockets. However, experiments with fully wetted crystals also showed the nucleation of bubbles on the crystal surface. Although microjet impingement on the crystal surface could not be directly visualized with high speed photography, scanning electron microscopy (SEM) analysis of irradiated calcite seeds showed deep circular indentations. It was suggested that these indentations might be caused by shockwave induced jet impingement. Furthermore, the appearance of voluminous fragments with large planes of fracture indicated that acoustic cavitation can also cause the breakage of single crystal structures.

Translational regulation of the plant S-adenosylmethionine decarboxylase

It is becoming apparent that control of protein synthesis by metabolites is more common than previously thought. Much of that control is exerted at the level of initiation of mRNA translation, orchestrated by upstream open reading frames (uORFs) and RNA secondary structure. S-Adenosylmethionine decarboxylase (AdoMetDC) is a key enzyme in polyamine biosynthesis and both mammalian and plant AdoMetDCs are translationally regulated by uORFs in response to polyamine levels by distinct mechanisms.

Arabidopsis polyamine biosynthesis: absence of ornithine decarboxylase and the mechanism of arginine decarboxylase activity

Unlike other eukaryotes, which can synthesize polyamines only from ornithine, plants possess an additional pathway from arginine. Occasionally non-enzymatic decarboxylation of ornithine could be detected in Arabidopsis extracts; however, we could not detect ornithine decarboxylase (ODC; EC 4. 1.1.17) enzymatic activity or any activity inhibitory to the ODC assay. There are no intact or degraded ODC sequences in the Arabidopsis genome and no ODC expressed sequence tags. Arabidopsis is therefore the only plant and one of only two eukaryotic organisms (the other being the protozoan Trypanosoma cruzi) that have been demonstrated to lack ODC activity. As ODC is a key enzyme in polyamine biosynthesis, Arabidopsis is reliant on the additional arginine decarboxylase (ADC; EC 4.1.1.9) pathway, found only in plants and some bacteria, to synthesize putrescine. By using site-directed mutants of the Arabidopsis ADC1 and heterologous expression in yeast, we show that ADC, like ODC, is a head-to-tail homodimer with two active sites acting in trans across the interface of the dimer. Amino acids K136 and C524 of Arabidopsis ADC1 are essential for activity and participate in separate active sites. Maximal activity of Arabidopsis ADC1 in yeast requires the presence of general protease genes, and it is likely that dimer formation precedes proteolytic processing of the ADC pre-protein monomer.

Rerouting the plant phenylpropanoid pathway by expression of a novel bacterial enoyl-CoA hydratase/lyase enzyme function

The gene for a bacterial enoyl-CoA hydratase (crotonase) homolog (HCHL) previously shown to convert 4-coumaroyl-CoA, caffeoyl-CoA, and feruloyl-CoA to the corresponding hydroxybenzaldehydes in vitro provided an opportunity to subvert the plant phenylpropanoid pathway and channel carbon flux through 4-hydroxybenzaldehyde and the important flavor compound 4-hydroxy-3-methoxybenzaldehyde (vanillin). Expression of the Pseudomonas fluorescens AN103 HCHL gene in two generations of tobacco plants caused the development of phenotypic abnormalities, including stunting, interveinal chlorosis and senescence, curled leaf margins, low pollen production, and male sterility. In second generation progeny, the phenotype segregated with the transgene and transgenic siblings exhibited orange/red coloration of the vascular ring, distorted cells in the xylem and phloem bundles, and lignin modification/reduction. There was depletion of the principal phenolics concomitant with massive accumulation of novel metabolites, including the glucosides and glucose esters of 4-hydroxybenzoic acid and vanillic acid and the glucosides of 4-hydroxybenzyl alcohol and vanillyl alcohol. HCHL plants exhibited increased accumulation of transcripts for phenylalanine ammonia-lyase, cinnamate-4-hydroxylase, and 4-coumarate:CoA ligase, whereas beta-1,3-glucanase was suppressed. This study, exploiting the ability of a bacterial gene to divert plant secondary metabolism, provides insight into how plants modify inappropriately accumulated metabolites and reveals the consequences of depleting the major phenolic pools.

Whole blood selenium in exudative age-related maculopathy

PURPOSE

We tested whether exudative ARM was associated with low whole blood levels of selenium (Se).

METHODS

Blood samples, drawn from 10 exudative ARM patients (61.2-76.1 yr) and 9 healthy-eyed (66.9-75.1 yr) subjects, were analyzed by atomic absorption spectroscopy.

RESULTS

Selenium concentration was significantly lower in the ARM group (186.6 microg/l) than in controls (207.0 microg/l). Because many ARM patients took Se supplements, we tested the effect on blood Se of 80 microg per day of sodium selenate. We found no enduring effects of supplementation for healthy-eyed, younger adults.

CONCLUSIONS

Significant group differences in this preliminary study indicate a larger-scale study of blood Se concentration in exudative ARM patients is warranted. If the effect of Se supplementation on the progression of exudative ARM is tested in future trials, it will be important to use organic Se, to identify the components of blood affected, and to observe protocol for at least six months.

A covariance structure analysis of flicker sensitivity

We tested whether linear structural models of the mechanisms underlying flicker sensitivity could reproduce the variance-covariance matrix of temporal contrast sensitivity data. Monocular sensitivities to frequencies between 2.5 and 45 Hz were measured for 124 subjects, ages 18-88 yr. Exploratory factor analyses revealed that both a two-mechanism and a three-mechanism model could adequately account for the data. Furthermore, confirmatory factor analyses and full structural equation models, using age as an explanatory variable, supported both models, with the three-factor model giving a somewhat better representation of the data. Parsimony favors the two-mechanism model. But patterns of loss associated with pre-exudative age-related maculopathy are more easily understood in terms of three underlying mechanisms.

Foveal flicker sensitivity in healthy aging eyes. II. Cross-sectional aging trends from 18 through 77 years of age

Foveal flicker contrast sensitivity was measured for healthy adults at temporal frequencies from 2.5 to 50 Hz. The first experiment compared two-interval forced-choice (2IFC) and yes-no detection (Y-N) testing procedures for younger (19-33-year-old) and older (67-73-year-old) observers. The 2IFC technique resulted in higher absolute estimates of sensitivity. However, within a method, relative differences were similar. Therefore the two methods gave similar estimates of temporal contrast-sensitivity change with age. Experiment 2 compared 89 observers from 18 through 77 years of age to explore the effect of the time course of aging on flicker sensitivity. The 2IFC procedure was used, and retinal illuminance changes with age were controlled. Significant overall losses in contrast sensitivity were found for the 45-54, 55-64, and 65-77-year-old age groups. Overall sensitivities for the 35-44-year-old group were comparable with or (not significantly) higher than those for the 18-24- and 25-34-year-old groups. The results suggested that (1) foveal temporal contrast sensitivity does not decline until after 44 years, (2) losses after 44 years are in amplitude but not in temporal resolution of the visual response, and (3) the mean rate of loss is approximately 0.78 decilog per decade after 44 years. These results are consistent with the existence of three phases of development of temporal contrast sensitivity over the life span. The results also emphasize the importance of including healthy-eyed age-matched controls in studies of flicker sensitivity in visual dysfunctions that affect mainly older adults.

Flicker sensitivity and fundus appearance in pre-exudative age-related maculopathy

PURPOSE

To evaluate whether foveal flicker sensitivity and fundus appearance are good predictors of exudative age-related maculopathy (ARM) when the effects of aging, retinal illuminance, and criterion differences are controlled.

METHODS

Fellow eyes of monocular exudative ARM patients were tested at baseline. Seven of these eyes have now developed exudative ARM. Therefore, at baseline they were in pre-exudative stages of ARM. The foveal flicker sensitivity and fundus appearance of the pre-exudative and nonconverted eyes were compared with healthy, age-matched eyes. The flicker stimulus was a uniform, 2.8 deg circular field at 660 nm, modulated sinusoidally at frequencies from 2.5 to 50 Hz. Fundus photographs were evaluated using the Wisconsin ARM grading system.

RESULTS

Flicker modulation sensitivity at two frequencies discriminated pre-exudative from healthy older eyes with 100% accuracy. Using the same criterion, pre-exudative eyes also were discriminated from nonconverted eyes with 100% accuracy. Whereas an overall fundus ARM risk score discriminated pre-exudative from healthy older eyes with 100% accuracy, it did not discriminate pre-exudative from nonconverted eyes at better than chance levels.

CONCLUSIONS

There were functional changes in the retina preceding development of exudative ARM. Foveal flicker sensitivity at low- to mid-temporal frequencies seemed highly sensitive to these pre-exudative changes in this relatively small group of subjects. The authors hypothesize that foveal flicker sensitivity is a good predictor of exudative ARM and a sensitive monitor of retinal function in pre-exudative ARM. These predictions are being tested on a larger, independent sample.

Mid-frequency loss of foveal flicker sensitivity in early stages of age-related maculopathy

Temporal contrast sensitivity in eyes at risk for exudative age-related maculopathy (ARM) was compared to that in age-matched healthy older eyes. The test stimulus was a foveally viewed, flickering, long-wavelength 2.8 degrees diameter circle in an equiluminant (photopic) surround. Retinal illuminance and decision criterion differences were experimentally controlled. Eyes in the healthy and ARM-risk groups had 20/30 or better Snellen acuity and intraocular pressure of less than 22 mmHg. Nevertheless, the ARM-risk patients were less sensitive to flicker contrast, especially for mid-temporal frequencies. This suggests that flicker sensitivity may be useful in identifying patients at risk for exudative ARM. In addition, comparison with other research reveals a paradox: Mid-temporal frequency sensitivity losses may be attributable primarily to a "high temporal frequency" mechanism.

Foveal flicker sensitivity discriminates ARM-risk from healthy eyes

The "good" eyes of 13 patients with monocular exudative ARM were compared with age-matched healthy eyes of 19 subjects. Membership in the two study groups was based upon careful clinical evaluation of the tested eye as well as upon status of the fellow eye. We asked whether temporal contrast sensitivity for a long-wavelength, low spatial frequency stimulus can be used to identify the group in which a given eye belongs. Using step-wise discriminant analysis, we found that the ARM-risk and healthy eyes could be classified with 78% accuracy on the basis of foveal flicker sensitivity at two temporal frequencies--14 and 10 Hz (in order of estimated weight.)

Preliminary evaluation of flicker sensitivity as a predictive test for exudative age-related maculopathy

Flicker contrast sensitivity was tested in the "good" eyes of 13 patients with monocular exudative age-related maculopathy (ARM). The stimulus was a foveal, long-wavelength, low spatial frequency 2.8 degrees circle in an equiluminant (photopic) surround. Two of these ARM-risk eyes have since developed exudative ARM. Compared to healthy age-matched eyes, the two eyes that developed exudative ARM had significantly lower sensitivity at 10-40 Hz up to 9 mo before exudative symptoms appeared. The implications of these results regarding the time-course of ARM and the predictive value of foveal contrast sensitivity testing are considered. Based upon data and theoretical considerations, the authors speculate that sensitivity loss between 10 and 40 Hz is a good predictor of which eyes will develop exudative ARM. This proposal will be tested by new data from current as well as new ARM-risk subjects.

Absolute thresholds in human infants exposed to continuous illumination

Continuous illumination at low-to-moderate photopic levels can cause damage to the visual system in nonhuman species. Therefore, the authors sought to determine whether behaviorally measurable visual deficits occurred in young human infants who had been exposed to long-term, continuous illumination in a neonatal intensive care unit (NICU). Using the forced-choice, preferential-looking technique, the authors measured absolute thresholds for detection of a 502 nm stimulus in nine preterm infants who had been exposed to 13 to 46 days of continuous room illumination. Nine infants born at term, who had experienced less than or equal to 5 days of continuous illumination, served as controls. The thresholds for the light-exposed and control infants did not differ. In addition, the light-exposed infants did not differ from control infants in their performance on a rapid acuity screening under photopic conditions. Thus, the present data provide no evidence of functional damage to either rod or cone vision in infants who had been exposed to continuous illumination in an NICU. Some limitations to the generality of these conclusions are discussed.

Practice improves adults' sensitivity to diagonals

Adults who were initially less sensitive to a diagonal, 10 c/deg sinusoidal grating, practiced detecting it for 3000 yes-no signal detection trials. Following practice all observers had improved their relative sensitivity to the diagonal and most were as sensitive to the diagonal as to cardinal (horizontal or vertical) orientations. Practicing a cardinal axis, on the other hand, caused no improvement in sensitivity unless the pre-practice threshold for that orientation was elevated with respect to other orientations. Three hypotheses are proposed to account for the improved sensitivity. The results are also related to the typical pattern of adult anisotropic contrast sensitivity which favors the cardinal orientations.

Non-astigmatic children's contrast sensitivities differ from anisotropic patterns of adults

Monocular contrast thresholds were estimated for horizontal (H), vertical (V) and left and right diagonal 10 c/deg sinusoidal gratings for non-astigmatic children (4:10--11:2 yr) and adults using yes-no signal detection (YN) methods. Some children were also tested with two-interval forced-choice (2IFC). Younger children were less likely to have the typical adult pattern of anisotropic sensitivity, favoring H and V, while 10--11 yr olds had more adult-like anisotropy. Within all age groups patterns of anisotropy varied considerably. Deviation of adults from the typical pattern may be related to small amounts of astigmatism in their untested eyes. 4- and 5-yr olds were confused by 2IFC. For children 6 yr and older, 2IFC and YN threshold estimates were equivalent, but 2IFC required less testing time.