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At least 721 records · Page 40Linked to original sources
PubMed1990

A computerized device for long-term measurements of the contraction frequency of cultured rat heart cells under stable incubating conditions.

A new computer-controlled measurement system for assessing beat rates of spontaneously contracting cultured heart cells is presented. The system overcomes several disadvantages of established techniques such as: (i) lack of precise control of the environment (pH, temperature, humidity); (ii) restriction to the measurement of one culture at a time; (iii) inability to obtain long-term measurements. The beat rate is recorded by subjecting monolayer cultures to dark field illumination and recording contraction-related changes in light scattering. A maximum of environmental stability is achieved because measurements are performed in the incubator. Beat rates of up to 16 individual culture dishes can be assessed repeatedly during freely selectable time intervals. Control of the experiments, data acquisition and data analysis are carried out by a computer. The specific advantage of the method lies in the ability to measure the beat rate of several culture dishes continuously over time intervals limited only by the viability of the cultures, i. e. up to several weeks.

Animals↗
PubMed1996

Differences in regional sweating responses during exercise between athletes trained on land and in water.

We investigated whether there are any differences in regional sweating responses during exercise between athletes trained on land and in water. We measured the local sweating rates on the left forearm (mswf) and the left scapula (msws), body temperatures (mean skin temperature, and rectal temperature Tre) in eight athletes trained on land (five soccer players, one distance runner and two baseball players, L group) and seven athletes trained in water (seven swimmers, W group) during cycle ergometer exercise at 50% maximal oxygen uptake for 40 min. The heart rate and oxygen uptake in the two groups during exercise showed nearly the same pattern of change. The Tre at the end of the exercise were 38.13 (SEM 0.19) degrees C in the L group and 38.26 (SEM 0.34) degrees C in the W group. Although the mswf in the two groups were similar, msws were significantly higher in L than in W at 30, 35 and 40 min of exercise. The msws at any given mean body temperature tended to be greater in L than in W. These results showed that a difference in regional sweating rate during exercise between the athletes trained on land and in water was present on the scapula.

Adult↗
PubMed1996

Regional differences in age-related decrements of the cutaneous vascular and sweating responses to passive heating.

Ten older (aged 64-76 years) and ten younger (aged 20-24 years) healthy men were exposed to a standard heat stress [by placing the lower legs and feet in a water bath at 42 degrees C while sitting in a controlled environment (ambient temperature 35 degrees C and 45% relative humidity) for 60 min]. During passive heating, the rectal temperature of the older men was significantly greater (P < 0.05) and mean skin temperature was lower (P < 0.001), compared to the younger men. Skin blood flow by laser Doppler flowmetry (LDF) was significantly lower on the chest and thigh for the older men (P < 0.001), but forehead LDF did not differ between the groups. The percentages of total LDF in the older men to total LDF in the younger men for the last 30 min were 99%, 58% and 50% on the forehead, chest and thigh, respectively. The age-related differences in LDF responses mirrored cutaneous vascular conductances (CVC), since no group and time effects were observed in mean arterial blood pressure during the test. During the last 30 min the local sweat rates (msw) on the back and thigh were significantly lower for the older men (P < 0.02), but not on forehead, chest and forearm, although the older men had lower msw during the first 30 min exposure regardless of site (P < 0.03). The percentages of total msw in the older men to total msw in the younger men during the last 30 min were 105%, 99%, 63%, 106% and 88% on the forehead, chest, thigh, forearm, and back, respectively. During the latter half of the exposure, the older men had similar LDF, CVC and msw on the forehead, lower LDF and CVC and a similar msw on the chest, and lower LDF, CVC and msw on the thigh, compared to the younger men. These results suggest firstly that regional differences exist in the age-related decrement of cutaneous vasodilatation as well as sweat gland function, secondly that the age-related decrement in cutaneous vascular function may precede a decrement in sweat gland function, and thirdly that the successive decrements may develop sequentially from the lower limbs to the upper body, and head.

Adult↗
PubMed1994

Metabolism of sulfate-reducing prokaryotes.

Dissimilatory sulfate reduction is carried out by a heterogeneous group of bacteria and archaea that occur in environments with temperatures up to 105 degrees C. As a group together they have the capacity to metabolize a wide variety of compounds ranging from hydrogen via typical organic fermentation products to hexadecane, toluene, and several types of substituted aromatics. Without exception all sulfate reducers activate sulfate to APS; the natural electron donor(s) for the ensuing APS reductase reaction is not known. The same is true for the reduction of the product bisulfite; in addition there is still some uncertainty as to whether the pathway to sulfide is a direct six-electron reduction of bisulfite or whether it involves trithionate and thiosulfate as intermediates. The study of the degradation pathways of organic substrates by sulfate-reducing prokaryotes has led to the discovery of novel non-cyclic pathways for the oxidation of the acetyl moiety of acetyl-CoA to CO2. The most detailed knowledge is available on the metabolism of Desulfovibrio strains, both on the pathways and enzymes involved in substrate degradation and on electron transfer components and terminal reductases. Problems encountered in elucidating the flow of reducing equivalents and energy transduction are the cytoplasmic localization of the terminal reductases and uncertainties about the electron donors for the reactions catalyzed by these enzymes. New developments in the study of the metabolism of sulfate-reducing bacteria and archaea are reviewed.

Archaea↗
PubMed1990

Effect of farm and simulated laboratory cold environmental conditions on the performance and physiological responses of lactating dairy cows supplemented with bovine somatotropin (BST).

A study was conducted to evaluate the effect of bovine somatotropin (BST) supplementation in twelve lactating dairy cows maintained in cold environmental conditions. Six cows were injected daily with 25 mg of BST; the other six were injected with a control vehicle. Cows were maintained under standard dairy management during mid-winter for 30 days. Milk production was recorded twice daily, and blood samples were taken weekly. Animals were then transferred to environmentally controlled chambers and exposed to cycling thermoneutral (15 degrees to 20 degrees C) and cycling cold (-5 degrees to +5 degrees C) temperatures for 10 days in a split-reversal design. Milk production, feed and water intake, body weights and rectal temperatures were monitored. Blood samples were taken on days 1, 3, 5, 8 and 10 of each period and analyzed for plasma triiodothyronine (T3), thyroxine (T4), cortisol, insulin and prolactin. Under farm conditions, BST-treated cows produced 11% more milk than control-treated cows and in environmentally controlled chambers produced 17.4% more milk. No differences due to BST in feed or water intake, body weights or rectal temperatures were found under laboratory conditions. Plasma T3 and insulin increased due to BST treatment while no effect was found on cortisol, prolactin or T4. The results showed that the benefits of BST supplementation in lactating dairy cows were achieved under cold environmental conditions.

Animals↗
PubMed1978

Changes in starch content and amylase zymograms during storage of Golden Delicious and Cox's Orange Pippin apples.

Changes in starch content and amylase zymograms were followed during storage of Golden Delicious and Cox's Orange Pippin apples. Although the former was stored at 3-4 degrees C under controlled atmosphere (3--4% O2; 7--8% CO2 by volume) and the latter in air at 17 degrees C, in both, the multiple forms of amylases remained active, even after the starch content decreased to zero. It is the lack of starch substrate, therefore, rather than of enzymes that limits the amylase action in the stored apple.

Amylases↗
PubMed1995

[Australian short-beaked echidna].

The Australian short-beaked echidna, a monotreme, is one of the oldest living mammals on earth. It is recorded to be the most widely distributed native mammal on the island continent and classed as 'common'. Yet, little is known about its natural history and biology in the wild. What science has learned about the echidna in the past 200 years and why there are still large gaps is reported here.

Animals↗
PubMed2003

Monitoring sweat calcium using skin patches.

The purpose of this study was to determine whether a simple noninvasive sweat collection method using skin patches would be useful in monitoring sweat Ca and to determine changes in dermal Ca loss during a bed rest study testing a resistive exercise countermeasure. The study showed that the technique was highly reproducible: the mean intra-subject variation approached zero and the inter-individual variability (%CV) varied from 18% to 32% for the three anatomical regions (arm, chest, and back) tested. There was less than 10% difference in sweat Ca excretion from different skin regions within the same individual at a given time point. A calculated estimate of total body sweat excretion for 12 bed rest subjects was 35 +/- 4 mg/day (mean +/- SE), close to published whole body measurements. Bed rest testing showed no significant differences with or without exercise when conducted in a temperature-controlled environment. We conclude that the skin patch technique is useful for monitoring changes in sweat Ca.

Adult↗
PubMed2005

Land use/cover changes, the environment and water resources in northeast China.

Land use/cover in Northeast China went through extensive changes during the 1990s. This report explores the interaction between these changes and the environment, and the implication of these changes for rational allocation of water resources. Two maps of land use/cover produced from 1990 and 2000 Landsat TM satellite images were overlaid in Arc Info to reveal changes in land cover. Results indicate that farmland and grassland decreased by 386,195 and 140,075 ha, respectively, while water, built-up areas, and woodland increased by 238,596, 194,231, and 192,682 ha, respectively. These changes bore a mutual relationship with the environmental change. On the one hand, climate warming made some of these changes (e.g., conversion of woodland and grassland to farmland) possible. On the other hand, the changed surface cover modified the local climate. These changes, in turn, caused severe environmental degradation and increased flooding. The change between dry field and rice paddy, in particular, raised severe implications for the proper allocation of limited water resources in the Northeast. Efforts are needed to coordinate their rational allocation to reap maximum and sustainable return over the entire area, not just in some localities. Results obtained in this study should be of interest to the international audience of Environmental Management in that they highlight the interactive nature of human activities and the environment and the off-site impact of these activities on the environment.

Agriculture↗
PubMed2003

Damaging UV radiation and invertebrate predation: conflicting selective pressures for zooplankton vertical distribution in the water column of low DOC lakes.

In nature most organisms have to manage conflicting demands of food gathering, predator avoidance, and finding a favorable abiotic environment (oxygen, temperature, etc.) in order to maximize their fitness. In the vertical water column of lakes with high solar ultraviolet radiation (UV) and invertebrate predators, zooplankton face two particularly strong and conflicting selective pressures. During daylight hours invertebrate predators often induce an upward vertical migration of zooplankton prey while potentially damaging UV forces a downward migration. We used 2.2 m long columns suspended vertically in a lake to conduct 2x2 factorial experiments to examine patterns of depth selection behavior by zooplankton in the presence and absence of both the invertebrate predator Chaoborus and UV. We hypothesized that Chaoborus and UV both affect the distribution of zooplankton and a combination of both factors would lead to a narrowing of depth distribution. We found that when Chaoborus were present zooplankton tended to be distributed at shallower depths in the columns, while in the presence of UV they exhibited a deeper distribution. Chaoborus themselves were always found near the bottom of the columns regardless of the UV treatment. Simultaneous exposure to predators and UV resulted in a peak of zooplankton (especially Daphnia catawba) distribution at intermediate depths. In a significant number of cases, depth range was narrowed in response to Chaoborus, UV, or both.

Animals↗
PubMed1980

Early postnatal development of wakefulness-sleep cycle and neuronal responsiveness: a multiunit activity study on freely moving newborn rat.

The development of the wakefulness-sleep cycle and neuronal responsiveness was studied on freely moving 1-, 3-, 5- and 7-day-old rats. Semimicroelectrodes were implanted under ether anaesthesia for multiunit activity (MUA) recording from the mesencephalic reticular formation (MRF) and basal forebrain area (FB). Following recovery from surgery and between the recording sessions pups were put back to the nest to be fed by their mothers. In a temperature-controlled environment continous MUA records were made between 16:00-18:00 and 19:00-21:00 h. In the MRF and FB the MUA was high during wakefulness, it decreased to a stable low level in quiet sleep and appeared to reach the highest values in paradoxical sleep. Neurone populations in the MRF and FB responded to somatosensory (air puffs), visual (flicker) and acoustic (1100 Hz) stimulation by a significant increase of MUA from the first day of life. In the MRF the rate of responsiveness increased during the first postnatal week; however, MUA responses to different stimuli exhibited different developmental time-courses. A high rate of responsiveness to each stimulus was characteristic of FB units. This neonatal 'supersensitivity' tended to decrease with age and the time-course of developmental changes proved to be modality-dependent.

Acoustic Stimulation↗
PubMed1988

Measured energy expenditure in critically ill infants and young children.

Technological limitations have impeded accurate energy expenditure assessment in critically ill infants and young children. Instead, a predicted energy expenditure (PEE) is derived based on weight, heat loss, activity, growth requirements, and degree of stress. This study compared actual measured energy expenditure (MEE) with conventional predicted values in 20 critically ill infants and children using a validated metabolic cart designed for use in this age group. All patients were studied either within 4 days of major surgery or during an acute disease process necessitating intensive care. All were severely stressed clinically and were studied while mechanically ventilated in a temperature-controlled environment. The study interval ranged from 1 to 12 hr and averaged 4 hr after a stabilization period of 30 min. The mean MEE was significantly lower than the mean PEE (52.2 +/- 16 kcal/kg/day vs 101.8 +/- 17 kcal/kg/day, P less than 0.001) with a mean MEE/PEE of 52.6 +/- 17% (range 26 to 92%). In a subgroup of 7 paralyzed patients, the mean MEE was significantly lower than in the 13 nonparalyzed patients when compared with PEE and predicted basal metabolic rate (PBMR). The coefficient of variance, conventionally recognized to be approximately 15% for PEE, averaged 6.35% for MEE in this study. These data indicate that if PEE is used as the sole guide for caloric repletion in the stressed infant or child, these patients will be substantially overfed.

Basal Metabolism↗