Short-Term in Situ Action of Melatonin on Ion Transport in Mice Kept at Restraint Stress

2015 ◽  
Vol 19 (1) ◽  
pp. 20 ◽  
Author(s):  
A. Sajeeb Khan ◽  
M. C. Subhash Peter
Keyword(s):  
Ion Transport ◽  
Restraint Stress ◽  
Short Term

In situ studies on alginic acid synthesis and other aspects of the metabolism of Laminaria digitata

1972 ◽  
Vol 50 (1) ◽  
pp. 177-184 ◽  
Author(s):  
Johan A. Hellebust ◽  
Arne Haug
Keyword(s):  
Amino Acids ◽  
Time Course ◽  
Alginic Acid ◽  
Acid Synthesis ◽  
Short Term ◽  
Fresh Weight Basis ◽  
Mannuronic Acid ◽  
Guluronic Acid ◽  
Rate Of Photosynthesis

Amino acids, particularly alanine and aspartate, become more strongly labeled than mannitol in short-term 14C-photoassimilation experiments. The amino acids are the most likely sources of carbon for alginic acid synthesis and respiration in the dark, in contrast to mannitol, which appears to be relatively unavailable. Temperature is very important in determining the rate of loss of recent photoassimilate in L. digitata. The rate of photosynthesis, on a fresh weight basis, is much higher for blades than for stipes.The time course for incorporation of photoassimilated carbon into alginate differs for the stipe and blade both in light and dark periods. Very little 14C enters alginate in blades in the dark, while alginate in stipes acquires considerable amounts of activity during dark periods. Alginate in both blade and stipe acquires 14C predominantly in mannuronic acid residues of their alginate during short-term photoassimilation periods, while guluronic acid residues become relatively more rapidly labeled during dark periods.

Structural basis of muscle O2 diffusing capacity: evidence from muscle function in situ

2000 ◽  
Vol 88 (2) ◽  
pp. 560-566 ◽  
Author(s):  
Russell T. Hepple ◽  
Michael C. Hogan ◽  
Creed Stary ◽  
Donald E. Bebout ◽  
Odile Mathieu-Costello ◽  
...  
Keyword(s):  
Gastrocnemius Muscle ◽  
Capillary Density ◽  
Structural Basis ◽  
Diffusing Capacity ◽  
Diffusion Distance ◽  
Short Term ◽  
Cross Sectional ◽  
Intact Organism ◽  
Minimal Reduction

Although evidence for muscle O2 diffusion limitation of maximal O2 uptake has been found in the intact organism and isolated muscle, its relationship to diffusion distance has not been examined. Thus we studied six sets of three purpose-bred littermate dogs (aged 10–12 mo), with 1 dog per litter allocated to each of three groups: control (C), exercise trained for 8 wk (T), or left leg immobilized for 3 wk (I). The left gastrocnemius muscle from each animal was surgically isolated, pump-perfused, and electrically stimulated to peak O2 uptake at three randomly applied levels of arterial oxygenation [normoxia, arterial[Formula: see text]([Formula: see text]) 77 ± 2 (SE) Torr; moderate hypoxia, [Formula: see text]: 33 ± 1 Torr; and severe hypoxia, [Formula: see text]: 22 ± 1 Torr]. O2 delivery (ml ⋅ min−1 ⋅ 100 g− 1) was kept constant among groups for each level of oxygenation, with O2 delivery decreasing with decreasing [Formula: see text]. O2extraction (%) was lower in I than T or C for each condition, but calculated muscle O2 diffusing capacity (Dm[Formula: see text]) per 100 grams of muscle was not different among groups. After the experiment, the muscle was perfusion fixed in situ, and a sample from the midbelly was processed for microscopy. Immobilized muscle showed a 45% reduction of muscle fiber cross-sectional area ( P < 0.05), and a resulting 59% increase in capillary density ( P < 0.05) but minimal reduction in capillary-to-fiber ratio (not significant). In contrast, capillarity was not significantly different in T vs. C muscle. The results show that a dramatically increased capillary density (and reduced diffusion distance) after short-term immobilization does not improve Dm[Formula: see text] in heavily working skeletal muscle.

scholarly journals Temporal Variation of Chlorophyll-a Concentrations in Highly Dynamic Waters from Unattended Sensors and Remote Sensing Observations

Sensors ◽  
2018 ◽  
Vol 18 (8) ◽  
pp. 2699 ◽  
Author(s):  
Jian Li ◽  
Liqiao Tian ◽  
Qingjun Song ◽  
Zhaohua Sun ◽  
Hongjing Yu ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Water Quality ◽  
Chlorophyll Fluorescence ◽  
Chlorophyll A ◽  
Temporal Variations ◽  
Lake Area ◽  
Short Term ◽  
Chl A ◽  
Spatio Temporal

Monitoring of water quality changes in highly dynamic inland lakes is frequently impeded by insufficient spatial and temporal coverage, for both field surveys and remote sensing methods. To track short-term variations of chlorophyll fluorescence and chlorophyll-a concentrations in Poyang Lake, the largest freshwater lake in China, high-frequency, in-situ, measurements were collected from two fixed stations. The K-mean clustering method was also applied to identify clusters with similar spatio-temporal variations, using remote sensing Chl-a data products from the MERIS satellite, taken from 2003 to 2012. Four lake area classes were obtained with distinct spatio-temporal patterns, two of which were selected for in situ measurement. Distinct daily periodic variations were observed, with peaks at approximately 3:00 PM and troughs at night or early morning. Short-term variations of chlorophyll fluorescence and Chl-a levels were revealed, with a maximum intra-diurnal ratio of 5.1 and inter-diurnal ratio of 7.4, respectively. Using geostatistical analysis, the temporal range of chlorophyll fluorescence and corresponding Chl-a variations was determined to be 9.6 h, which indicates that there is a temporal discrepancy between Chl-a variations and the sampling frequency of current satellite missions. An analysis of the optimal sampling strategies demonstrated that the influence of the sampling time on the mean Chl-a concentrations observed was higher than 25%, and the uncertainty of any single Terra/MODIS or Aqua/MODIS observation was approximately 15%. Therefore, sampling twice a day is essential to resolve Chl-a variations with a bias level of 10% or less. The results highlight short-term variations of critical water quality parameters in freshwater, and they help identify specific design requirements for geostationary earth observation missions, so that they can better address the challenges of monitoring complex coastal and inland environments around the world.

Changes in glucocorticoid receptor mRNA in the developing ovine pituitary and the effects of exogenous cortisol

1995 ◽  
Vol 144 (3) ◽  
pp. 483-490 ◽  
Author(s):  
S G Matthews ◽  
K Yang ◽  
J R G Challis
Keyword(s):  
Glucocorticoid Receptor ◽  
Late Gestation ◽  
Developmental Changes ◽  
Pars Intermedia ◽  
Pars Distalis ◽  
Short Term ◽  
Neonatal Life ◽  
Inferior Aspect ◽  
Glucocorticoid Receptor Mrna

Abstract Developmental changes in pituitary glucocorticoid receptor (GR) mRNA were examined during gestation and early neonatal life using in situ hybridization. Pituitaries were harvested from sheep fetuses at days 60–80, 100–120, 130–135, 140–142 and term, and from lambs of days 0–7 and 30–60, and adults. GR mRNA was present in the pars distalis by day 60, levels increased through gestation, and there was a redistribution of GR mRNA, resulting in a relatively greater abundance at the base of the pars distalis. At term, there was a significant (P<0·05 compared with the day 140–142 fetuses) elevation of GR mRNA, which was maintained in the newborn lamb, reaching highest levels at days 30–60 of neonatal life. GR mRNA was undetectable in the pars intermedia until day 120, but subsequently increased to high levels at term. Interestingly, the expression of GR mRNA in the pars intermedia dropped precipitously in the newborn (P<0·05 compared with term), though levels recovered in the older lambs and adults. The regional and cellular distribution of GR mRNA correlated closely with the presence of immuno-reactive GR (irGR) in the pituitary; the majority of irGR was present in the nuclei. Intrafetal infusion of cortisol (12 h; 5 μg/min) in late gestation (day 135) had no effect on GR mRNA expression in either the pars distalis or pars intermedia. These results indicated that, in the fetal pituitary, (1) the GR gene is expressed in both the pars distalis and pars intermedia, (2) levels of GR mRNA in the fetal pituitary correlated with the distribution of nuclear irGR, (3) GR mRNA is present at higher levels in the inferior aspect of the pars distalis, its abundance increases immediately prior to parturition and is maintained in the newborn, and (4) cortisol infusion for 12 h does not affect GR mRNA in either region of the pituitary, suggesting that, in the short term, glucocorticoids do not directly regulate GR synthesis. Journal of Endocrinology (1995) 144, 483–490

Phosphofructokinase activity and acidosis during short-term tetanic contractions

1991 ◽  
Vol 69 (2) ◽  
pp. 298-304 ◽  
Author(s):  
Lawrence L. Spriet
Keyword(s):  
Glycolytic Enzyme ◽  
Test Tube ◽  
Mammalian Skeletal Muscle ◽  
Short Term ◽  
Short Supply ◽  
In Vivo Experiments ◽  
Anaerobic Energy

Anaerobic energy production is essential for the production of muscular tension when the demand for energy is greater than can be provided aerobically and when oxygen is in short supply. The largest source of anaerobic energy is from the glycolytic pathway. With sustained tetanic contractions, muscle glycolytic activity is high and hydrogen ions (H+) accumulate while tension production decreases. The increasing [H+] and decreasing tension led to the suggestion that H+ inhibits the activity of the regulatory glycolytic enzyme phosphofructokinase (PFK). Early in vitro work confirmed the H+ sensitivity of PFK in the test tube, indicating that little PFK activity should persist at a pH of 6.9–7.0. However, in situ and in vivo experiments suggested that significant PFK activity was maintained during intense contractions when muscle pH decreased to 6.4–6.6. There are several concerns associated with the application of in vitro findings to in vivo exercise situations: (i) there is little in vitro work in mammalian skeletal muscle with substrate and modulator concentrations representative of exercise, (ii) most in vitro analyses of PFK activity are performed following the dilution of the enzyme in mediums with low protein concentration, and (iii) do the modulators identified in vitro exist in high enough in vivo concentrations at rest and during exercise to contribute to the regulation of PFK? More recent in vitro and in situ PFK experiments have overcome some of these concerns. They confirm that during intense, short-term tetanic contractions, PFK activity is well matched to the ATP demand despite decreases in pH to ~6.4–6.5. A combination of decreased inhibitor (ATP) and increased substrate (fructose 6-phosphate) contents coupled with increases in the contents of several positive modulators may be responsible for the maintained PFK activity. This combination reduces the pH-dependent ATP inhibition of PFK and extends the physiological pH range of the enzyme to the range normally measured during this type of muscular activity.Key words: glycolysis, phosphofructokinase, anaerobic metabolism, acidosis.

An Energetics Model for Lake Trout, Salvelinus namaycush: Application to the Lake Michigan Population

1983 ◽  
Vol 40 (6) ◽  
pp. 681-698 ◽  
Author(s):  
Donald J. Stewart ◽  
David Weininger ◽  
Donald V. Rottiers ◽  
Thomas A. Edsall
Keyword(s):  
Lake Michigan ◽  
Lake Trout ◽  
Salvelinus Namaycush ◽  
High Energy ◽  
Alosa Pseudoharengus ◽  
Fishing Mortality ◽  
Age Classes ◽  
Short Term ◽  
Conversion Efficiencies

An energetics model is implemented for lake trout, Salvelinus namaycush, and applied to the Lake Michigan population. It includes an egestion function allowing any proportional mix of fish and invertebrates in the diet, a growth model accounting for both ontogenetic and seasonal changes in energy-density of predator and prey, a model for typical in situ swimming speed, and reproductive energy losses due to gametes shed. Gross conversion efficiency of energy by lake trout over their life (21.8%) is about twice the efficiency of converting biomass to growth because they store large amounts of high-energy fats. Highest conversion efficiencies are obtained by relatively fast-growing individuals, and over half the annual energy assimilated by older age-classes may be shed as gametes. Sensitivity analysis indicates a general robustness of the model, especially for estimating consumption by fitting a known growth curve. Largest sensitivities were for the intercept and weight dependence coefficients of metabolism. Population biomass and associated predatory impact of a given cohort increase steadily for about 3.5 yr then decline steadily after fishing mortality becomes important in the fourth year in the lake. This slow response time precludes manipulation of lake trout stocking densities as a means to control short-term prey fluctuations. Predation by lake trout on alewife, Alosa pseudoharengus, has been increasing steadily since 1965 to about 8 400 t∙yr−1, and is projected to rise to almost 12 000 t∙yr−1 by 1990.

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