Effects of Dielectrophoresis on Growth, Viability and Immuno-reactivity of Listeria monocytogenes

Dielectrophoresis (DEP) has been regarded as a useful tool for manipulating biological cells prior to the detection of cells. Since DEP uses high AC electrical fields, it is important to examine whether these electrical fields in any way damage cells or affect their characteristics in subsequent analytical procedures. In this study, we investigated the effects of DEP manipulation on the characteristics of Listeria monocytogenes cells, including the immuno-reactivity to several Listeria-specific antibodies, the cell growth profile in liquid medium, and the cell viability on selective agar plates. It was found that a 1-h DEP treatment increased the cell immuno-reactivity to the commercial Listeria species-specific polyclonal antibodies (from KPL) by ~31.8% and to the C11E9 monoclonal antibodies by ~82.9%, whereas no significant changes were observed with either anti-InlB or anti-ActA antibodies. A 1-h DEP treatment did not cause any change in the growth profile of Listeria in the low conductive growth medium (LCGM); however, prolonged treatments (4 h or greater) caused significant delays in cell growth. The results of plating methods showed that a 4-h DEP treatment (5 MHz, 20 Vpp) reduced the viable cell numbers by 56.8–89.7 %. These results indicated that DEP manipulation may or may not affect the final detection signal in immuno-based detection depending on the type of antigen-antibody reaction involved. However, prolonged DEP treatment for manipulating bacterial cells could produce negative effects on the cell detection by growth-based methods. Careful selection of DEP operation conditions could avoid or minimize negative effects on subsequent cell detection performance.     

Interactions of molecular probes with living cells and tissues. Part 1. Some general mechanistic proposals,making use of a simplistic Chinese box model

Summary A simple and generalised model — termed the simplistic Chinese box [SCB] model — for the interaction of molecular probes with living systems is described. The SCB model includes the following assumptions. That living systems may be considered as built from biologically defined boxes, e.g. whole cell nucleus nucleoli. That movement of molecular probes into and through these boxes is strongly infuenced by box wall permeability, which in turn is largely dependent on the simple physicochemical properties of probe and wall. That retention of probes in boxes is influenced by permeability of the walls and by trapping of probes by boxes and walls, the latter effect also being strongly dependent on simple physicochemical, properties. That important physicochemical properties include electric charge, hydrophilicity/lipophilicity, non-specific protein binding, and molecular size. That, since all these factors can be expressed or modelled numerically, SAR methodology is an appropriate technique for analysing molecular probe investigations. This paper is dedicated to the memory of Prof. A.W. Rogers     

Mechanism of nitrogen effect on zinc nutrition of flooded rice

Summary Nitrogen application increased Zn contents of flooded rice on two calcareous soils. Urea and (NH₄)₂SO₄ being better N carriers than NH₄NO₃ resulted in higher increase. Nitrogen enhanced Zn contents partly through growth promotion but mainly by increasing soil Zn solubility and root efficiency for Zn absorption. Zinc solubility rose by an enigmatic mechanism and not from pH reduction or soluble Zn-HN₃ complex formation as occurs for upland plants. Nitrogen aggravated Zn retention in upland plant roots as immobile Zn-protein complex was not important for rice. Bicarbonate inhibition of Zn uptake by rice from CO(NH₂)₂ application or its stimulation by lower redox potential from NH₄NO₃ addition were not involved.No. V in the series Micronutrient availability to cereals from calcareous soils.     

Micronutrient availability to cereals from calcareous soils

Summary By contrast of strong phosphorus-zinc antagonism in upland crops, P strongly enhanced Zn uptake in flooded rice on a calcareous soil. Radioisotopic studies indicated increase to occur preferentially from applied Zn fertilizer. Phosphorus appeared to stimulate uptake predominantly by enhancing Zn concentration in soil solution and by increasing metabolic Zn absorption by plant roots. The ‘A’ value was not a reliable measure of labile soil Zn for rice as it markedly changed with levels of P and Zn fertilizers. No. VI in the series: Phosphorus-zinc interaction in rice. No. VI in the series: Phosphorus-zinc interaction in rice.     

Tissue culture of Alhagi camelorum – a legume of high regenerative capacity

Alhagi camelorum cultures provide a system with a high propensity for plantlet regeneration from root, hypocotyl, stem, and leaf explants. Excluding leaf explants, all explants regenerate to form shoot-buds on a simple basal medium suggesting a differential morphogenic potential of different parts of the same plant. All parts of the plant including leaves, form shoot-buds on cytokinin-containing media which markedly promote shoot-bud differentiation, alone or in combination with indoleacetic acid or naphthaleneacetic acid. Rooting occurs on media containing indoleacetic acid and naphthaleneacetic acid. 2, 4-Dichlorophenoxyacetic acid is inhibitory for differentiation and induces callusing. Callus induced on benzylaminopurine and 2,4-dichlorophenoxyacetic acid differentiates to form shoot-buds on transfer to cytokinin-containing medium. Upon transfer to basal medium shoots produce roots. Plants have been transferred to soil.     

Effect of month and season of calving on the length of subsequent calving interval in Nili-Ravi buffaloes

Data pertaining to records of 1,274 calving intervals for 400 breeding buffaloes maintained at the Livestock Experiment Station, Qadirabad, District Sahiwal (Pakistan), were analyzed to investigate the magnitude of influence of month and season of calving on the length of subsequent calving interval. The longest average calving interval of 609.9 days was recorded for buffaloes calving in January, while the shortest average calving interval of 502.8 days was observed for those calving in June, the difference being highly significant (P < 0.01). When the data were split in accordance with season of calving, the calving intervals for buffaloes calving in winter, spring, summer and autumn averaged 569.1, 570.6, 506.6 and 515.7 days, respectively. The differences between intervals for winter and spring calvings and between intervals for summer and autumn calvings were non-significant. All other differences were highly significant (P < 0.01). Thus, in most of the buffaloes calving in winter or spring, the first post-partum oestrus and conception are delayed till the following autumn or winter, resulting in significantly longer calving intervals. In contrast, animals calving in summer or autumn exhibit post-partum heat and conception during autumn or winter, resulting in shorter calving intervals.     

Production of tylosin in solid-state fermentation by Streptomyces fradiae NRRL-2702 and its gamma-irradiated mutant (γ-1)

Aims:  To develop solid-state fermentation system (SSF) for hyper production of tylosin from a mutant γ-1 of Streptomyces fradiae NRRL-2702 and its parent strain.
Methods and Results:  Various agro-industrial wastes were screened to study their effect on tylosin production in SSF. Wheat bran as solid substrate gave the highest production of 2500 μg of tylosin g⁻¹ substrate by mutant γ-1 against parent strain (300 μg tylosin g⁻¹ substrate). The tylosin yield was further improved to 4500 μg g⁻¹ substrate [70% moisture, 10% inoculum (v/w), pH 9·2, 30°C, supplemental lactose and sodium glutamate on day 9]. Wild-type strain displayed less production of tylosin (655 μg of tylosin g⁻¹ substrate) in SSF even after optimization of process parameters.
Conclusion:  The study has shown that solid-state fermentation system significantly enhanced the tylosin yield by mutant γ-1.
Significance and Impact of the Study:  This study proved to be very useful and resulted in 6·87 ± 0·30-fold increase in tylosin yield by this mutant when compared to that of wild-type strain.     

Production of haploid plantlets in anther cultures of Albizzia lebbeck L.

Anthers of Albizzia lebbeck on B₅ medium (BM) supplemented with kinetin (2 mg/l) and 2, 4-D (0.5 mg/l) showed callus initiation from microspores. Differentiation of embryoids and shoots was obtained on BM + BAP (1 mg/l) + IAA (0.5 mg/l) and of roots on BM. Root tip squashes of the regenerated plantlets showed the haploid chromosome number (n=13), confirming the microspore origin of the regenerants.