Indirect hand and forearm vasomotion: Regional variations in cutaneous thermosensitivity during normothermia and mild hyperthermia

In this experiment, hand and forearm vasomotor activity was investigated during localised, but stable heating and cooling of the face, hand and thigh, under open-loop (clamped) conditions. It was hypothesised that facial stimulation would provoke the most potent vascular changes. Nine individuals participated in two normothermic trials (mean body temperature clamp: 36.6 °C; water-perfused suit and climate chamber) and two mildly hyperthermic trials (37.9 °C). Localised heating (+5 °C) and cooling (−5 °C) stimuli were applied to equal surface areas of the face, hand and thigh (perfusion patches: 15 min), while contralateral forearm or hand blood flows (venous-occlusion plethysmography) were measured (separate trials). Thermal sensation and discomfort votes were recorded before and during each thermal stimulation. When hyperthermic, local heating induced more sensitive vascular responses, with the combined thermosensitivity of both limb segments averaging 0.011 mL·100 mL⁻¹·min⁻¹·mmHg⁻¹·°C⁻¹, and 0.005 mL·100 mL⁻¹·min⁻¹·mmHg⁻¹·°C⁻¹ during localised cooling (P<0.05). Inter-site comparisons among the stimulated sites yielded minimal evidence of variations in local thermal sensation, and no differences were observed for vascular conductance (P>0.05). Therefore, regional differences in vasomotor and sensory sensitivity appeared not to exist. When combined with previous observations of sudomotor sensitivity, it seems that, during mild heating and cooling, regional representations within the somatosensory cortex may not translate into meaningful differences in thermal sensation or the central integration of thermoafferent signals. It was concluded that inter-site variations in the cutaneous thermosensitivity of these thermolytic effectors have minimal physiological significance over the ranges investigated thus far.     

Effects of fluorescent dyes, quenchers, and dangling ends on DNA duplex stability

Single and dual-labeled fluorescent oligodeoxynucleotides are used in many molecular biology applications. We investigated the effects of commonly used fluorescent dyes and quenchers on the thermodynamic stability of a model probe-target DNA duplex. We demonstrate that those effects can be significant. Fluorescent dyes and quenchers were attached to the probe ends. In certain combinations, these groups stabilized the duplex up to 1.8kcal/mol and increased T(m) up to 4.3 degrees C. None of the groups tested significantly destabilized the duplex. Rank order of potency was, starting with the most stabilizing group: Iowa Black RQ approximately Black Hole 2>Cy5 approximately Cy3>Black Hole 1>QSY7 approximately Iowa Black FQ>Texas Red approximately TAMRA>FAM approximately HEX approximately Dabcyl>TET. Longer linkers decreased stabilizing effects. Hybridizations to targets with various dangling ends were also studied and were found to have only minor effects on thermodynamic stability. Depending on the dye/quencher combination employed, it can be important to include thermodynamic contributions from fluorophore and quencher when designing oligonucleotide probe assays.     

Effects of repeated short-term cold exposures on cold induced thermogenesis of women

The effects of repeated exposures to resting cold air (10°C) on the shivering and thermogenic responses of women to standard cold stress were investigated. Ten women, aged 18 to 34 years, were divided into two groups of five women each. One group, the acclimated (A) was exposed ten times within 2 weeks, the first and the last exposures being the pre-and post-tests respectively. The second group, the control (C) was exposed twice within 18 days. Measurements of rectal and skin temperatures, oxygen uptake, time to onset of shivering (TOS), and perceived cold were performed during all exposures. Shivering responses were evaluated by electromyography and visually. A significant (P<0.05), increase was seen in TOS (from 26.2 min to 55.6 min), and a significant decrease was seen in thermoregulatory heat production (from 14.78 kcal/h to –2.64 kcal/h) in group A; these changes were evident after about five exposures. It is concluded that the women became cold acclimated as a result of the repeated short-term resting cold air exposures.Research supported by Capes/Brazil, and by the Universidade Federal de Minas Gerais/Brazil     

A longitudinal large-scale objective sleep data analysis revealed a seasonal sleep variation in the Japanese population

In the contemporary era, when life habits are largely determined by social needs and individual preferences, sleep is nevertheless affected by seasonal environmental changes. Japan has large seasonal and geographical alterations of photoperiod and climate. Japan does not adopt the daylight saving time (DST) system, making it a suitable country for the study of seasonal variations in natural human sleep. The aim of this study was to analyze the seasonal changes in the sleep properties (timing and quality) and identify their relationship with environmental changes. Here, we report an analysis of objective sleep data of 691 161 nights collected from 1856 Japanese participants (age 20–79 years, male 91%, female 9%) for 3 years using contactless biomotion sensors. Sleep onset time did not show clear seasonal variation, but sleep offset time showed a seasonal change with a single latest peak in winter. Seasonal variation was larger during weekends than during weekdays. Sleep offset time well correlated with sunrise time but was different in spring and autumn even when the sunrise time was same, suggesting the role of temperature difference. Sleep quality, estimated by wake time after sleep onset and sleep efficiency, showed seasonal changes with the lowest trough around mid-summer. In conclusion, despite profound social influences, the timing and quality of sleep showed seasonal fluctuation indicating that they were influenced by climate factors even in the developed country.     

Evaluation of satellite retrievals of water quality parameters for Lake Victoria in East Africa

Lake Victoria in East Africa is a major ecosystem, whose size and importance has warranted the exploration of MODIS imagery to provide continuous and accurate water quality information. To this effect, two sea expeditions (in November 2014 and February 2015) were carried out to collect in situ lake surface temperature (LST), chlorophyll a (Chl) and Secchi disk depth (SDD) to compare with the corresponding satellite derived variables. Comparisons were made based on the following error matrices: coefficient of correlation (r), mean square error (MSE), root mean square error (RMSE), mean absolute deviation (MAD) and mean absolute percent error (MAPE). In general the results showed that satellite derived LST gives a good estimate of in situ LST. Conversely, the error matrices indicated that satellite derived Chl yielded more uncertainty when compared with in situ Chl. This could be because of the fact that the MODIS Chl product algorithm was designed for oceans and may not be appropriate for inland lakes. Satellite derived SDD compared fairly well with in situ SDD. From these results it is evident that with more in situ observations and improved algorithms, MODIS can be useful to improve how water quality is monitored on Lake Victoria.     

Microdistribution of chironomids (Diptera: Chironomidae) in Alpine streams: an autoecological perspective

Chironomid communities from three glacial and three non-glacial high mountain streams in three Alpine river basins were analyzed (Conca, Niscli, Cornisello, NE Italy, 46°N, 10°E). Eighteen sampling reaches belonging to five stream types (kryal, subkryal, glacio-rhithral, kreno-rhithral, outlet) were investigated. At each reach, geomorphological, physical, chemical and biological data were collected. Field surveys were carried out during three periods per year from 1996 to 1998: immediately after spring snowmelt, in mid-summer and in early autumn. In all, 439 zoobenthos samples were collected from 5 to 10 microhabitats of 0.1m² in each reach and date using a standard pond net (mesh size of 250m). About 50% of individuals collected were chironomids (26673 specimens, 53 taxa), with densities ranging from 4 to 2652indm^–2. With few exceptions, they dominated as number of taxa and individuals in all reaches. Chironomid subfamilies Diamesinae and Orthocladiinae were most abundant, especially in glacial reaches, where Diamesa spp. constituted up to 100% of the total fauna. Chironomid distribution was analyzed in relation to 37 abiotic variables, referring to stream origin, hydrology, geomorphology, physics and chemistry. Diamesa steinboecki, D. latitarsis gr. A and Pseudokiefferiella parva were the taxa best associated with glacial conditions (i.e. high channel instability or presence of bedrock, high suspended solids and total phosphorous content, low conductivity and silica content, highly variable diel discharge and low mean temperature), while Pseudodiamesa branickii, Corynoneura spp., Eukiefferiella spp., Parorthocladius nudipennis, Tvetenia calvescens/bavarica, Thienemaniella spp. and Micropsectra atrofasciata were mostly associated with non-glacial conditions. Substratum particle size, water depth, current velocity, the presence of riffles/pools and of mosses/algae (Hydrurus foetidus) were the major factors affecting microdistribution of chironomids in the investigated streams.     

Factors affecting the daily rhythm of body temperature of captive mouse lemurs (<Emphasis Type="Italic">Microcebus murinus</Emphasis>)

Microcebus murinus, a small nocturnal Malagasy primate, exhibits adaptive energy-saving strategies such as daily hypothermia and gregarious patterns during diurnal rest. To determine whether ambient temperature (T_a), food restriction and nest sharing can modify the daily body temperature (T_b) rhythm, T_b was recorded by telemetry during winter in six males exposed to different ambient temperatures (T_a=25, 20, 15°C) and/or to a total food restriction for 3 days depending on social condition (isolated versus pair-grouped). At 25°C, the daily rhythm of T_b was characterized by high T_b values during the night and lower values during the day. Exposure to cold significantly decreased minimal T_b values and lengthened the daily hypothermia. Under food restriction, minimal T_b values were also markedly lowered. The combination of food restriction and cold induced further increases in duration and depth of torpor bouts, minimal T_b reaching a level just above T_a. Although it influenced daily hypothermia less than environmental factors, nest sharing modified effects of cold and food restriction previously observed by lengthening duration of torpor but without increasing its depth. In response to external conditions, mouse lemurs may thus adjust their energy expenditures through daily modifications of both the duration and the depth of torpor.     

Heat stress effects on ribulose-1,5-bisphosphate carboxylase/oxygenase,Rubisco binding protein and Rubisco activase in wheat leaves

Changes in chlorophyll content, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) binding protein (RBP), Rubisco activase (RA), Rubisco large (LS) and small (SS) subunits, and electrolyte leakage were investigated in wheat leaf segments during heat stress (HS) for 1 h and for 24 h at 40 °C in darkness or in light, as well as after recovery from heat stress (HSR) for 24 h at 25 °C in light. The 24-h HS treatment in darkness decreased irreversibly photosynthetic pigments, soluble proteins, RBP, RA, Rubisco LS and SS. An increase in RA and RBP protein contents was observed under 24-h HS and HSR in light. This increase was in accordance with their role as chaperones and the function of RBP as a heat shock protein.This work was partially supported by Swiss National Science Foundation (Project 31-55289.98).     

Photosynthetic response of Nereocystis luetkeana (Phaeophyta) to high light

Photosynthetic response to high light was determined for Bull kelp, Nereocystis luetkeana (K. Mertens) Postels and Ruprecht in order to understand how this species is affected by short‐term fluctuations in irradiance. Exposure of N. luetkeana blades to high intensity photosynthetically active radiation (1000 µmol photons m^?2 s^–1) caused increased non‐photochemical quenching of fluorescence and higher de‐epoxidation ratios for xanthophyll pigments indicating that energy‐quenching xanthophylls were used to protect blades against photoinhibition. Despite initiation of these photoprotective mechanisms, maximum photochemical efficiency of photosystem II (F_v/F_m) decreased 40% in response to a 60 min exposure to 1000 µmol photons m^?2 s^–1 photosynthetically active radiation indicating that photoinhibition had occurred. Light‐saturated rates of oxygen evolution were not changed significantly by the high light treatment. Recovery of maximum photochemical efficiency of photosystem II to within 8% of initial values occurred after a 300‐min dim light period. Younger sections of the blades were slightly more susceptible to high light damage than older sections. Middle sections of the blades were more prone to light‐induced damage at water temperatures of 7°C or 18°C, as compared to 13°C. Exposure to biologically effective ultraviolet‐B radiation (UV‐B_be) (up to 4.5 kJ m^–2 day^–1) in photoinhibitory light conditions did not significantly affect light‐induced damage to photosystem II.