An efficient,inexpensive elutriator design for separating benthos from sediment samples

A design for an elutriator is given. The elutriator has an efficiency of 96.1 ± 3.5% in sorting mixed invertebrates from sandy sediments in five minute trial runs. It is easily constructed from PVC pipe and fittings which are available in most hardware stores at low cost. It can also be adapted for portable use in the field.     

An inexpensive water circulation system for studies of chemical exchange using intact sediment cores

SUMMARY. 1. An inexpensive pumping and reservoir system has been developed for circulating water over intact sediment cores. The system facilitates both measurement and manipulation of supernatant properties and flow velocities.
2. The apparatus has been used to evaluate the effect of flow velocity and pH on nutrient exchange at the sediment-water interface.     

An inexpensive blood pressure-heart rate computer for laboratory or teaching use.

A special-purpose analog computer circuit is described that, given a signal proportional to arterial blood pressure, generates signals equal to systolic, diastolic, pulse, and mean pressure at a calibration of 100 mmHg/V. Heart period and rate are also derived at calibration of 1 s/V and 100 bpm/V, respectively. The outputs are step-function beat-by-beat changes in these six variables suitable either for analog recording, or presentation to a panel meter for digital display.     

Immunofluorescence detection of the denitrifying strain Pseudomonas stutzeri (ATCC 14405) in seawater and intertidal sediment environments

A strain-specific immunofluorescence assay for enumeration of a marine denitrifying bacterium was developed and applied in the marine environment. The polyclonal antiserum for Pseudomonas stutzeri (ATCC 14405) did not react with other pseudomonads, other heterotrophs, or autotrophic nitrifying strains. The abundance of P. stutzeri in the shallow water column of Monterey Bay was less than 0.1% of the total bacterial abundance and decreased with depth, whereas the total bacterial abundance was variable and nearly constant with depth. P. stutzeri was also detected in the sediments of a microbial mat from Tomales Bay. The relatively low contribution of P. stutzeri to the total bacterial abundance in both environments implies that it is not a major component of the heterotrophic assemblage. This conclusion appears to hold for most other strains for which specific assays have been applied in the marine environment. The isolation of several different denitrifying strains from local marine environments implies that the culturable population is quite diverse, even in the absence of different selective enrichment media. Thus, strain specific immunofluorescence is of limited use in quantifying functional groups of bacteria. Conversely, they provide specific information on the diversity of natural populations and their relation to culturable strains.Offprint requests to: B. Ward     

Determination of equilibrium and individual rate constants for subtilisin-catalyzed transesterification in anhydrous environments

We report here the first determinations of individual rate constants and equilibrium constants for enzymatic reactions in essentially anhydrous organic solvents. Using the added nucleophile method we have measured the effect of changing solvent on the binding and catalytic steps for subtilisin-catalyzed transesterification of N-protected amino acid esters. The detailed information generated indicates that once the substrate has bound to the enzyme, the catalytic machinery can work at rates equivalent to those in water. The decreased overall rates for subtilisin suspended in anhydrous solvents are merely the result of extremely high values for K(s), in most cases, coupled with low concentrations of nucleophile ( approximately 1.0M in organic solvents, and 55M in water). The method described, which is generally applicable, and straightforward experimentally, will, we believe, enable a clearer understanding of how changing solvent can predictably affect the activity and specificity of the enzyme. (c) 1992 John Wiley & Sons, Inc.     

Long-term measurement of heart rate in chicken eggs

Taking advantage of acoustocardiogram (ACG), we measured the heart rate (HR) of chick embryos continuously from day 12 until hatching and then investigated the development of HR irregularities (HRI), HR variability (HRV), and the existence of a circadian rhythm in mean HR (MHR). HRI comprised transient bradycardia and tachycardia, which first developed on day 14 and 16 in most embryos, respectively. Transient bradycardia increased in frequency and magnitude with embryonic development and occurred over periods of up to 30 min in some embryos. MHR was maximal on around days 14-15 and thereafter decreased to about 250-260 bpm on days 16-18. Baseline HRV, which is an oscillation of the MHR baseline, occurred as HR decreased from days 15-16 and became predominant on days 17-18. The magnitude of the baseline oscillations reached up to 50 bpm in some embryos and the period ranged between about 40-90 min (ultradian rhythm). A circadian rhythm of MHR was not found in late chick embryos. On days 18-19, embryonic activities were augmented and then breathing movements began to occur, disturbing ACG signals and thus making it difficult to measure the HR. Instead, the development of breathing activities was recorded. Breathing frequency was irregular at first and then increased to a maximum of about 1.5 Hz prior to hatching.     

A method for long-term measurement of respiration in intertidal fishes during simulated intertidal conditions

Aquatic and aerial respiration of the amphibious fishes Lipophrys pholis and Periophthalmus barbarus were examined using a newly designed flow-through respirometer system. The system allowed long-term measurements of oxygen consumption and carbon dioxide release during periods of aquatic and aerial respiration. The M o ₂ of L. pholis , measured at 15° C, was 2·1 μmol O₂ g^–1 h^–1 during aquatic and 1·99 μmol O₂ g^–1 h^–1 during aerial exposure. The corresponding values of the M co₂ were 1.67 and 1.59 μmol O₂ g^–1 h^–1 respectively, giving an aquatic respiratory exchange ratio (RER) of 0·80 and an aerial RER of 0·79. The M o₂ of P. barbarus , measured at 28°C, was 4·05 μmol O₂ g^–1 h^–1 during aquatic and 3·44 μmol O₂ g^–1 h^–1 during aerial exposure. The corresponding values of the Mco₂ were 3·29 μmol CO₂ g^–1 h^–1 and 2·63 μmol CO₂ g^–1 h^–1 respectively, giving an aquatic RER of 0·81 and an aerial RER of 0·77. While exposed to air for at least 10 h, both species showed no decrease in metabolic rate or carbon dioxide release. The RER of these fishes equalled their respiratory quotient. After re-immersion an increased oxygen consumption, due to the payment of an oxygen debt, could not be detected.     

Fate of elemental sulfur in an intertidal sediment

Abstract: Sediment from a tidal flat at Wedderwarden, near the mouth of the Weser estuary, northern Germany, was amended with elemental sulfur, and concentrations of metabolic end products were monitored. The production of both sulfate and sulfide was consistent with disproportionation as the most important fate of the added elemental sulfur. A population of bacteria conducting active elemental sulfur disproportionation was also enriched from the sediment. In the enrichments, containing both elemental sulfur and Fe oxides as a sulfide 'scrub', sulfide and sulfate were produced in a ratio of     , somewhat lower than the predicted ratio of     . The mismatch between predicted and observed production ratios is explained by the channelling of electrons into autotrophic or mixotrophic CO₂ fixation rather than sulfide formation. The production of organic carbon, in the correct amount to explain the observed sulfide to sulfate production ratio, was verified by organic carbon analysis. Finally, rates of sulfate reduction were identical in the elemental sulfur amended sediment, and in control sediment with no added sulfur. Hence, the heterotrophic bacterial community was completely unaffected by an active metabolism conducting elemental sulfur disproportionation.     

Simple, inexpensive attainment and measurement of very high cooling and warming rates

We have developed a simple, inexpensive system (<$300 US) for measuring cooling and warming rates of small (∼ 0.1 μl) aqueous samples at rates as high as 10⁵ °C/min. The measurement system itself, can track rates approaching one million °C/min. For temperature sensing, a Type T thermocouple with 50 μm wire was used. The thermocouple output voltage was read with an inexpensive USB based digital oscilloscope interfaced to a laptop computer, and the raw data were processed with MS Excel.     

An inexpensive replacement for dry ice in the laboratory

A reusable inexpensive replacement for dry ice in laboratory use is presented. Commercially available small pellets of stone or metal can be stored in a −80 °C freezer and used for quickly freezing small samples with a freezing rate that is actually somewhat faster than with dry ice itself. Following use, the material is returned to the freezer to re-chill until the next usage.     

Estimating the feeding rate of the bedbug Cimex lectularius in an infested room: an inexpensive method and a case study

The common bedbug, Cimex lectularius L. (Hemiptera: Cimicidae), is a globally re-emerging pest that is playing an increasing role in legal disputes and compensation claims as a result of its unpleasant feeding activity. However, there is little information about the feeding frequency of bedbugs outside controlled laboratory cultures. Here, we present a simple method of estimating the average time since the last bloodmeal of individual female bedbugs in a single sampling event, applicable to a single bedbug harbourage or an entire room. Using the temperature-dependent rate of decrease in the abdomen size of the bedbug after a bloodmeal, we found that, in a highly infested room kept at a constant temperature of 26°C, females fed every 2.5 days on average. Our method corrects for variations in body size across different populations and determines the shrinkage that occurs when individuals are preserved in ethanol. This method should, therefore, be widely applicable. It is cheap, rapid and, if coupled with information on the total number of bedbugs present in a room, allows for the estimation of the minimum number of times persons lodging in a room have been bitten by bedbugs. This method can also be used to calculate the feeding rate of other blood-sucking insects on their hosts. The sex ratio in the infestation was female-biased. Finally, our case study suggests that individual female bedbugs within a harbourage do not seem to feed at a regular rate, but tend to synchronize feeding patterns.     

Beyond growth rate 0.6: Corynebacterium glutamicum cultivated in highly diluted environments

Fast growth of industrial microorganisms, such as Corynebacterium glutamicum, is a direct amplifier for the productivity of any growth coupled or decoupled production process. Recently, it has been shown that C. glutamicum when grown in a novel picoliter bioreactor (PLBR) exhibits a 50% higher growth rate compared to a 1 L batch cultivation [Grünberger et al. (2012) Lab Chip]. We here compare growth of C. glutamicum with glucose as substrate at different scales covering batch cultivations in the liter range down to single cell cultivations in the picoliter range. The maximum growth rate of standard batch cultures as estimated from different biomass quantification methods is ${\hat {\mu }} = 0.42\pm 0.03\,{\rm h}^{- 1} $ even for microtiter scale cultivations. In contrast, growth in a microfluidic perfusion system enabling analysis of single cells reproducibly reveals a higher growth rate of ${\hat {\mu }} = 0.62\pm 0.02\,{\rm h}^{- 1} $ . When in the same perfusion system cell‐free supernatant from exponentially grown shake flask cultures is used the growth rate of single cells is reduced to ${\hat {\mu }} = 0.47\pm 0.02\,{\rm h}^{- 1} $ . Likewise, when fresh medium is additionally supplied with 5 mM acetate, a growth rate of ${\hat {\mu }} = 0.51\pm 0.01\,{\rm h}^{- 1} $ is determined. These results prove that higher growth rates of C. glutamicum than known from typical batch cultivations are possible, and that growth is definitely impaired by very low concentrations of byproducts such as acetate. Biotechnol. Bioeng. 2013; 110: 220–228. © 2012 Wiley Periodicals, Inc.     

The measurement of resting metabolic rate in preschool children

Objective: This study examined the repeatability of measuring resting metabolic rate (RMR) in preschool children and the effect of different calculation protocols. Research Methods and Procedures: Eleven children (4 females and 7 males) participated in the project. They were recruited through advertisements in local schools and community centers. Resting metabolic rate was measured on 3 occasions over a 2‐week period, each after an overnight fast and each lasting ～20 to 25 minutes. Results were compared using repeated‐measures ANOVA to check for repeatability, and a number of methods of calculating RMR were assessed. Results: Repeatability of RMR measurements was good (coefficient of variation of replicates, 6.8%), with no significant difference between days of measurement. The lowest RMR measurement was obtained when the first 10 minutes were excluded and periods during which large activity was observed were excluded. This measurement was, on average, 4% lower than averaging the measurements after the first 5 minutes, including body movements. Discussion: This study suggests that RMR can be measured in preschool children and that the best method for calculating RMR in these subjects is to exclude periods when large body movements occur and the first 10 minutes of the measurement period. Only a single measurement of RMR is needed to obtain a reliable estimate.     

An inexpensive method for remotely monitoring nest activity

ABSTRACT.   In studies of avian nest success, investigators often face the difficult task of periodically checking nest status while at the same time limiting observer influence on nest survival. Remotely monitoring nests using temperature data loggers is one method that allows for continuous data capture regarding nest status (i.e., active vs. inactive) without the negative effects associated with repeated nest checks. We used small temperature data loggers (Thermochron iButtons) to remotely monitor nests of Long-billed Curlews ( Numenius americanus ) in northeastern Nevada. Data loggers programmed to record temperature at 10-min and 20-min intervals were placed in curlew nests. Data loggers were set to collect data throughout the nesting cycle to determine onset of incubation and timing of nest failure. On average, Long-billed Curlews began incubating approximately 3 d after the first egg was laid and onset of incubation coincided with the laying of the third egg. iButtons allowed us to determine when incubation was terminated in 17 of 23 unsuccessful Long-billed Curlew nests, including 13 of 17 depredated nests. The presence of iButtons in Long-billed Curlew nests did not affect daily survival rate, egg hatchability or rate of nest abandonment. iButtons are an efficient and practical means for remotely monitoring nests of large egg-laying birds, such as the Long-billed Curlew.     

An inexpensive camera system for monitoring cavity nests

ABSTRACT A variety of pole‐mounted cameras have been developed for monitoring nest cavities. However, currently available camera systems may either be prohibitively expensive or difficult to assemble. I developed an inexpensive (<$500 US) and easily assembled camera system that allows researchers to monitor cavity nests from the ground. The system consists of a small camera, a cable connecting the camera to a ground‐level power source and laptop computer, and a flexible neck connecting the camera to a telescoping pole. During a study of Red‐headed Woodpeckers (Melanerpes erythrocephalus), I used this camera to inspect 16 nests and found that the images were clear and allowed accurate counts of eggs and nestlings. This camera system uses standard, off‐the‐shelf components, and can easily be altered. The design is not appropriate for humid or dense‐canopy environments because of the inclusion of a laptop and its wired design. However, this design makes the system inexpensive and allows researchers to save, edit, and view nest inspection recordings.     

Reaction kinetics in intracellular environments with macromolecular crowding: simulations and rate laws

We review recent evidence illustrating the fundamental difference between cytoplasmic and test tube biochemical kinetics and thermodynamics, and showing the breakdown of the law of mass action and power-law approximation in in vivo conditions. Simulations of biochemical reactions in non-homogeneous media show that as a result of anomalous diffusion and mixing of the biochemical species, reactions follow a fractal-like kinetics. Consequently, the conventional equations for biochemical pathways fail to describe the reactions in in vivo conditions. We present a modification to fractal-like kinetics following the Zipf–Mandelbrot distribution which will enable the modelling and analysis of biochemical reactions occurring in crowded intracellular environments.