Short communication: Storage time and temperature affect plasma osmolality values in field-collected blood samples

As climate change alters the hydric regime of many habitats, understanding the hydric physiology of animals becomes increasingly important. Plasma osmolality is a popular metric to assess an organism's hydration, but samples often need to be stored before being analyzed, under varying conditions and for different lengths of time. Previous studies on plasma storage conditions, and how they impact sample integrity, are minimal and have focused more on clinical applications than field studies. We studied the stability of osmolality values from wild rattlesnake plasma samples stored in commonly used plastic snap-cap tubes under different time (0, 2, 3, 7, 29 days) and temperature (refrigerated at 2 °C and frozen at -18 °C) treatments. We hypothesized that frozen samples would remain more stable (e.g., retain osmolality values more similar to baseline values) than refrigerated samples because freezing the plasma would reduce evaporation. We found that osmolality of samples increased over time at both temperatures, becoming significantly higher than baseline after 7 days. Contrary to our prediction, osmolality increased more in frozen samples than in refrigerated samples. We discuss possible reasons for our results, along with their implications. To obtain the most accurate plasma osmolality values, we recommend refrigerating plasma samples for as short a time as possible, 3 days or fewer, before analyzing them on an osmometer.

Differing field methods and site conditions lead to varying bias in suspended sediment concentrations in the Lower Mississippi and Atchafalaya Rivers

At sites that have been sampled for decades, changes in field and laboratory methods happen over time as instrumentation and protocols improve. Here, we compare the influence of depth- and point-integrated sampling on total, fine (< 0.0625 mm), and coarse (≥ 0.0625 mm) suspended sediment (SS) concentrations in the Lower Mississippi and Atchafalaya Rivers. Using historical field method information, we identified seven sites to test such differences. We found SS samples collected using point-integration tended to have higher concentrations than those collected using depth-integration. However, the presence and magnitude of the bias were inconsistent across sites. Bias was present at the site with less-than-ideal conditions (i.e., non-trapezoidal channel, non-uniform flow) and non-existent at the ideal site location, indicating the bias between sampling methods depends on site sampling conditions. When present, the bias is greater at higher concentrations and at moderate to high flows. At the less-than-ideal site, point-integrated samples can have 16% (total) and 34% (coarse) higher concentrations than depth-integrated samples. When flow effects are removed, this translates to a bias of 19, 9, and 8 mg per liter for total, fine, and coarse SS. When a change in field methods occurs, comparison samples and a rigorous evaluation of those samples are warranted to determine the proper course of action for a particular site. Often, the effect and solution will not be known until several years of comparison samples have been collected under a variety of hydrologic conditions.

Monitoring exercise intensity in diabetes: applicability of "heart rate-index" to estimate oxygen consumption during aerobic and resistance training

PURPOSE

Accurate quantification and monitoring of exercise "dose", described by oxygen consumption (VO₂), is necessary for exercise prescription and individualization. However, due to the complexity and elevated cost of direct, gold-standard methods, this is rarely done outside research laboratories. Heart rate-index (HR_index) is a new simple method to estimate VO₂ in healthy and clinical populations. We tested the performance of HR_index to estimate VO₂ in diabetic patients during aerobic (AT) and isotonic training (IT).

METHODS

Data from 12 males (age: 64 ± 5 years; BMI: 26 ± 12) with type 2 diabetes were analysed. VO₂ and heart rate were measured during one AT and one IT session. Furthermore, VO₂ was indirectly estimated based on HR_index. Then, the correspondence between measured and estimated VO₂ was evaluated by two-way RM-ANOVA, correlation and Bland-Altman analysis.

RESULTS

Estimated average VO₂ values during AT (1292 ± 366 ml/min) were not different from (p = 0.243) and highly correlated with (r = 0.87, p < 0.001) the measured values (1369 ± 417 ml/min), with a small bias and imprecision. Conversely during IT, HR_index overestimated VO₂ compared to the actual measures (1048 ± 404 vs 667 ± 230 ml/min, p ≤ 0.001) and only a moderate correlation was found between values (r = 0.43, p ≤ 0.001), with a large bias and imprecision.

CONCLUSION

VO₂ of aerobic exercises can be accurately estimated in diabetes patients using HR_index. During isotonic exercise, this method is not recommended for monitoring metabolic intensity due to large overestimation and imprecision. In aerobic exercise, HR_index offers a simple and valid alternative to the direct VO₂ determination and may favour the applicability of time-resolved measures of exercise "dose".

Tryptophan-like fluorescence as a measure of microbial contamination risk in groundwater

Microbial water quality is frequently assessed with a risk indicator approach that relies on Escherichia coli. Relying exclusively on E. coli is limiting, particularly in low-resource settings, and we argue that risk assessments could be improved by a complementary parameter, tryptophan-like fluorescence (TLF). Over two campaigns (June 2016 and March 2017) we sampled 37 water points in rural Kwale County, Kenya for TLF, E. coli and thermotolerant coliforms (total n = 1082). Using three World Health Organization defined classes (very high, high, and low/intermediate), risk indicated by TLF was not significantly different from risk indicated by E. coli (p = 0.85). However, the TLF and E. coli risk classifications did show disagreement, with TLF indicating higher risk for 14% of samples and lower risk for 13% of samples. Comparisons of duplicate/replicate results demonstrated that precision is higher for TLF (average relative percent difference of duplicates = 14%) compared to culture-based methods (average RPD of duplicates ≥ 26%). Additionally, TLF sampling is more practical because it requires less time and resources. Precision and practicality make TLF well-suited to high-frequency sampling in low resource contexts. Interpretation and interference challenges are minimised when TLF is measured in groundwaters, which typically have low dissolved organic carbon, relatively consistent temperature, negligible turbidity and pH between 5 and 8. TLF cannot be used as a proxy for E. coli on an individual sample basis, but it can add value to groundwater risk assessments by improving prioritization of sampling and by increasing understanding of spatiotemporal variability.

Burial, excavation, and preparation of primate skeletal material for morphological study

Inclusion of osteological material in primatological research has a long history, and use of skeletal remains continues to be important in anatomical and anthropological research. Here we report a set of proven methods, including equipment, protocol, and procedure, which enable relatively simple acquisition of skeletal material from naturally deceased animals in field sites and sanctuaries. Such skeletal material, often with extensive accompanying life-history data, is a unique and valuable source of data for both academic and conservation-based research.

Moving your laboratories to the field--Advantages and limitations of the use of field portable instruments in environmental sample analysis

The recent rapid progress in technology of field portable instruments has increased their applications in environmental sample analysis. These instruments offer a possibility of cost-effective, non-destructive, real-time, direct, on-site measurements of a wide range of both inorganic and organic analytes in gaseous, liquid and solid samples. Some of them do not require the use of reagents and do not produce any analytical waste. All these features contribute to the greenness of field portable techniques. Several stationary analytical instruments have their portable versions. The most popular ones include: gas chromatographs with different detectors (mass spectrometer (MS), flame ionization detector, photoionization detector), ultraviolet-visible and near-infrared spectrophotometers, X-ray fluorescence spectrometers, ion mobility spectrometers, electronic noses and electronic tongues. The use of portable instruments in environmental sample analysis gives a possibility of on-site screening and a subsequent selection of samples for routine laboratory analyses. They are also very useful in situations that require an emergency response and for process monitoring applications. However, quantification of results is still problematic in many cases. The other disadvantages include: higher detection limits and lower sensitivity than these obtained in laboratory conditions, a strong influence of environmental factors on the instrument performance and a high possibility of sample contamination in the field. This paper reviews recent applications of field portable instruments in environmental sample analysis and discusses their analytical capabilities.