Screening environmental samples for source-specific bacteriophage hosts using a method for the simultaneous pouring of 12 petri plates

A simple apparatus was developed to allow 12 petri plates to be poured simultaneously by hand. It was used when screening bacterial isolates from sewage and dog feces for their ability to detect phages from these sources. This was done to assess the ease with which source-specific phage hosts can be isolated from these sources of fecal pollution. Host bacteria that consistently detected phages from sewage were easily isolated from sewage. These bacterial isolates did not detect phages from dog feces. Host bacteria were not isolated from dog feces even after screening hundreds of colonies from fecal samples from six dogs. Journal of Industrial Microbiology & Biotechnology (2000) 24, 124–126. Received 06 July 1999/ Accepted in revised form 05 November 1999     

Leveling the playing field: Evaluation of a portable instrument for quantifying balance performance

Balance is a complex, sensorimotor task requiring an individual to maintain the center of gravity within the base of support. Quantifying balance in a reliable and valid manner is essential to evaluating disease progression, aging complications, and injuries in clinical and research settings. Typically, researchers use force plates to track motion of the center of gravity during a variety of tasks. However, limiting factors such as cost, portability, and availability have hindered postural stability evaluation in these settings. This study compared the “gold standard” for assessing postural stability (i.e., the laboratory-grade force plate) to a more affordable and portable assessment tool (i.e., BTrackS balance plate) in healthy young adults. Correlations and Bland-Altman plots between the center of pressure outcome measures derived from these two instruments were produced. Based on the results of this study, the measures attained from the portable balance plate objectively quantified postural stability with high validity on both rigid and compliant surfaces, demonstrated by thirty-five out of thirty-eight observed postural stability metrics in both surface conditions with a correlation of 0.98 or greater. The low cost, portable system performed similarly to the lab-grade force plate indicating the potential for practitioners and researchers to use the BTrackS balance plate as an alternative to the more expensive force plate option for assessing postural stability, whether in the lab setting or in the field.     

Induced current measurements in whole body exposure condition to radio frequency electric fields.

The current induced in a human exposed to radio frequency electric fields has been studied by the use of a stripline, in which whole body exposure to vertical electric fields (3-27 MHz) can be produced. We have examined two different techniques to measure the induced current; parallel plate meters and current probes. When the subject has good connection to the ground, the choice of measurement technique is not crucial, since there are only minor differences in readings between the instruments. But when the subject is wearing shoes and/or standing on a wooden plate, the difference between the instruments increases considerably. The difference can mainly be explained by the capacitive coupling between the parallel plate meters and the ground; therefore, the current probes are preferred when the subject does not have perfect contact with the ground. Since the International Commission on Non-Ionizing Radiation Protection guidelines demand measurements of induced current in humans exposed to radio frequency fields in the range of 10-110 MHz, the importance of finding an appropriate measurement procedure becomes apparent.     

Role of cell-cycle in regulating neuroepithelial cell shape during bending of the chick neural plate

Summary Neuroepithelial cells transform from spindle-shaped to wedge-shaped within the median and paired dorsolateral hinge points of the bending neural plate, but the mechanisms underlying these localized changes are unclear. This study was designed to evaluate further the hypothesis that localized wedging of neuroepithelial cells during bending involves basal cellular expansion resulting from alteration of the cell-cycle. Neurulating chick embryos were treated with tritiated thymidine, and transverse sections through the midbrain were examined autoradiographically. Parameters of the cell-cycle as well as nuclear position and size were assessed in the median hinge point, which contains predominantly wedge-shaped cells, and in adjacent lateral areas of the neural plate, which contain predominantly spindle-shaped cells. Both the DNA-synthetic phase and non-DNA synthetic portion of the cell-cycle were significantly longer in the median hinge point than in lateral neuroepithelial areas, some nuclei in both regions were located basally during these phases, and virtually all basal nuclei in the median hinge point were large. Additionally, the mitotic phase was significantly shorter in the median hinge point than in lateral areas. We present a model to explain how alteration of the cell-cycle in the median hinge point could generate wedging of cells in this region.     

Na+ and K+ fluxes stimulated by Na+-coupled glucose transport: Evidence for a Ba2+-insensitive K+ efflux pathway in rabbit proximal tubules

Summary Addition of glucose or the nonmetabolizable analogue -methyl-d-glucoside to rabbit proximal tubules suspended in a glucoseand alanine-free buffer caused a sustained increase in intracellular Na⁺ content (+43±7 nmol · (mg protein)^–1) and a concomitant but larger decrease in K⁺ content (–72±11 nmol· (mg protein)^–1). A component of the net K⁺ efflux was Ba²⁺ insensitive, and was inhibited by high (1mm) but not low (10 m) concentrations of the diuretics, furosemide and bumetanide. The increase in intracellular Na⁺ content is consistent with the view that the increased rates of Na⁺ and water transport seen in the proximal tubule in the presence of glucose can be attributed (at least in part) to a stimulation of basolateral pump activity by an increased [Na⁺] _i .     

Ca2+-activated K+ conductance causes membrane hyperpolarizations in a monkey kidney cell line (JTC-12)

Summary We have previously reported hyperpolarizing membrane potential changes in a monkey kidney cell line (JTC-12) which has characteristics resembling proximal tubular cells. These hyperpolarizations could be observed spontaneously or evoked by mechanically touching adjacent cells. In this report, we have shown further evidence that these hyperpolarizations are elicited by an increase in membrane conductance to K⁺ which is caused by an increase in cytosolic Ca²⁺ concentration. In addition, we have found another type of hyperpolarization which is evoked by applying flow of extracellular fluid to the cell. Intracellular injection of Ca²⁺ and Sr²⁺ evoked hyperpolarizations, while intracellular injection of Mn²⁺ and Ba²⁺ did not. Intracellular injection of EGTA suppressed both spontaneous and mechanically evoked hyperpolarizations. In Ca²⁺-free medium, both spontaneous and flow-evoked hyperpolarizations were not observed, while mechanical stimuli consistently evoked hyperpolarization. In Na⁺-free medium, the incidence of cells showing the spontaneous or flow-evoked hyperpolarization increased, and the amplitude and the duration of the mechanically evoked hyperpolarization became greater. Quinidine inhibited all types of hyperpolarization. These data suggest that hyperpolarizations in JTC-12 cells are due to an increase in Ca²⁺-activated K⁺ conductance.     

An in vitro test for measuring cytotoxicity of mercuric chloride to human kidney epithelial cells by specific enzyme release

Mercuric compound toxicity is well documented in animals and man for practically all organs. The recent development of cell culture techniques appeared as a novel fruitful tool in toxicology, especially in renal toxicology. Heavy metal induced renal cell alterations can be evaluated by membrane permeability damages.The present study evaluates mercuric chloride nephrotoxic effect in human kidney epithelial cells by measuring the release of two specific nephrotoxicity marker enzymes, Gamma Glutamyl Transferase (GGT) and Alkaline Phosphatase (ALP) in the culture medium. Cultured kidney epithelial cells were exposed to different HgCl₂ concentrations (5, 10, 20, and 50 g). Cultures were examined after 6 and 24 hours exposure. A good correlation between mercury dose and toxic effect, and exposure time and toxic effect was found. Enzymes were significantly released into the culture medium for 5 g and 10 g HgCl₂/ml after 6 hours exposure; and after 24 hours exposure, enzymes were released for 5 g/ml only.It appears that the specific tubular enzyme release in the culture medium is a good in vitro test for quantification of specific tubular damage.