The gut microenvironment of helicid snails (Gastropoda: Pulmonata): in-situ profiles of pH, oxygen, and hydrogen determined by microsensors

2003 ◽  
Vol 81 (5) ◽  
pp. 928-935 ◽  
Author(s):  
Maryvonne Charrier ◽  
Andreas Brune
Keyword(s):  
Respiratory Activity ◽  
Helix Pomatia ◽  
Distal Intestine ◽  
Biochemical Processes ◽  
Oxygen Gradients ◽  
Uptake Rates ◽  
Cornu Aspersum ◽  
Ph Microelectrodes ◽  
Liquid Ion Exchanger

In-situ profiles of pH, oxygen, and hydrogen were measured in isolated guts of starved terrestrial gastropods belonging to four species, Cornu aspersum (syn. Helix aspersa), Elona quimperiana, Helix pomatia, and Helix lucorum (excepted pH), using Clark-type oxygen and hydrogen microsensors and liquid-ion-exchanger pH microelectrodes. The pH profiles in the two phyllophagous species, H. pomatia and C. aspersum, increased by 0.9 and 1.4 from the crop to the distal intestine (pH 6.4 and 7.4, respectively). In the saprophagous E. quimperiana, as in H. pomatia, the pH along the gut axis remained acidic (5.1–6.6), suggesting saprophagous habits in the latter. In all four species, no oxygen was detected in the gut lumen. Nevertheless, steep oxygen gradients around the gut epithelium indicated high oxygen-uptake rates. The estimated respiratory activity of the intestine ranged between 6.5 (E. quimperiana) and 13.1 (H. lucorum) μmol O2·g fresh mass–1·h–1. Hydrogen accumulated in the intestine and digestive gland of all snails tested, with the highest values in E. quimperiana and H. pomatia (58 and 78 μM, respectively). These results provide the basis for a better understanding of the microbial and biochemical processes involved in digestion.

3-D imaging of cells using a confocal laser scanning microscope and digital image processing

1988 ◽  
Vol 46 ◽  
pp. 96-97
Author(s):  
Thomas M. Jovin ◽  
Michel Robert-Nicoud ◽  
Donna J. Arndt-Jovin ◽  
Thorsten Schormann
Keyword(s):  
Laser Scanning ◽  
Confocal Laser Scanning Microscope ◽  
Laser Scanning Microscopy ◽  
Confocal Laser Scanning ◽  
Confocal Laser ◽  
Scanning Microscope ◽  
Laser Scanning Microscope ◽  
Biochemical Processes ◽  
Adjacent Structures

Light microscopic techniques for visualizing biomolecules and biochemical processes in situ have become indispensable in studies concerning the structural organization of supramolecular assemblies in cells and of processes during the cell cycle, transformation, differentiation, and development. Confocal laser scanning microscopy offers a number of advantages for the in situ localization and quantitation of fluorescence labeled targets and probes: (i) rejection of interfering signals emanating from out-of-focus and adjacent structures, allowing the “optical sectioning” of the specimen and 3-D reconstruction without time consuming deconvolution; (ii) increased spatial resolution; (iii) electronic control of contrast and magnification; (iv) simultanous imaging of the specimen by optical phenomena based on incident, scattered, emitted, and transmitted light; and (v) simultanous use of different fluorescent probes and types of detectors.We currently use a confocal laser scanning microscope CLSM (Zeiss, Oberkochen) equipped with 3-laser excitation (u.v - visible) and confocal optics in the fluorescence mode, as well as a computer-controlled X-Y-Z scanning stage with 0.1 μ resolution.

scholarly journals Effect of incubation time and substrate concentration on N-uptake rates by phytoplankton in the Bay of Bengal

2005 ◽  
Vol 2 (5) ◽  
pp. 1331-1352
Author(s):  
S. Kumar ◽  
R. Ramesh ◽  
S. Sardesai ◽  
M. S. Sheshshayee
Keyword(s):  
Incubation Time ◽  
Uptake Rate ◽  
Nitrate Uptake ◽  
N Uptake ◽  
Marine Phytoplankton ◽  
Total Production ◽  
New Production ◽  
Urea Uptake ◽  
Uptake Rates

Abstract. We report here the results of three experiments, which are slight variations of the 15N method (JGOFS protocol) for determination of new production. The first two test the effect of (i) duration of incubation time and (ii) concentration of tracer added on the uptake rates of various N-species (nitrate, ammonium and urea) by marine phytoplankton; while the third compares in situ and deck incubations from dawn to dusk. Results indicate that nitrate uptake can be underestimated by experiments where incubation times shorter than 4h or when more than 10% of the ambient concentration of nitrate is added prior to incubation. The f-ratio increases from 0.28 to 0.42 when the incubation time increases from two to four hours. This may be due to the observed increase in the uptake rate of nitrate and decrease in the urea uptake rate. Unlike ammonium [y{=}2.07x{-}0.002\\, (r2=0.55)] and urea uptakes [y{=}1.88x{+}0.004 (r2=0.88)], the nitrate uptake decreases as the concentration of the substrate (x) increases, showing a negative correlation [y{=}-0.76x+0.05 (r2=0.86)], possibly due to production of glutamine, which might suppress nitrate uptake. This leads to decline in the f-ratio from 0.47 to 0.10, when concentration of tracer varies from 0.01 to 0.04μ M. The column integrated total productions are 519 mg C m-2 d-1 and 251 mg C m-2 d-1 for in situ and deck incubations, respectively. The 14C based production at the same location is ~200 mg C m-2 d-1, which is in closer agreement to the 15N based total production measured by deck incubation.

scholarly journals First in situ estimations of small phytoplankton carbon and nitrogen uptake rates in the Kara, Laptev, and East Siberian seas

2018 ◽  
Author(s):  
Bhavya P. Sadanandan ◽  
Jang Han Lee ◽  
Ho Won Lee ◽  
Jae Joong Kaang ◽  
Jae Hyung Lee ◽  
...  
Keyword(s):  
Sea Ice ◽  
Nitrogen Uptake ◽  
N Uptake ◽  
Total Carbon ◽  
The Arctic ◽  
Carbon And Nitrogen ◽  
Uptake Rates ◽  
Wide Range ◽  
Small Phytoplankton

Abstract. Carbon and nitrogen uptake rates by small phytoplankton (0.7–5 μm) in the Kara, Laptev, and East Siberian seas in the Arctic Ocean were quantified using in situ isotope labelling experiments for the first time as part of the NABOS (Nansen and Amundsen Basins Observational System) program during August 21 to September 22, 2013. The depth integrated C, NO3−, and NH4+ uptake rates by small phytoplankton showed a wide range from 0.54 to 15.96 mg C m−2 h−1, 0.05 to 1.02 and 0.11 to 3.73 mg N m−2 h−1, respectively. The contributions of small phytoplankton towards the total C, NO3−, and NH4+ was varied from 24 to 89 %, 32 to 89 %, and 28 to 89 %, respectively. The turnover times for NO3− and NH4+ by small phytoplankton during the present study point towards the longer residence times (years) of the nutrients in the deeper waters, particularly for NO3−. Relatively, higher C and N uptake rates by small phytoplankton obtained during the present study at locations with less sea ice concentrations points towards the possibility of small phytoplankton thrive under sea ice retreat under warming conditions. The high contributions of small phytoplankton towards the total carbon and nitrogen uptake rates suggest capability of small size autotrophs to withstand in the adverse hydrographic conditions introduced by climate change.

In situ micropuncture study of pancreatic duct pH

1980 ◽  
Vol 238 (3) ◽  
pp. G263-G268 ◽  
Author(s):  
C. R. Caflisch ◽  
S. Solomon ◽  
W. R. Galey
Keyword(s):  
Chloride Concentration ◽  
Flow Conditions ◽  
Buffer Solutions ◽  
Micropuncture Study ◽  
Glass Membrane ◽  
Rabbit Pancreas ◽  
Alkaline Fluid ◽  
Ph Microelectrodes ◽  
Chloride Concentrations

The pH and chloride concentration in the extralobular duct system of the rabbit pancreas was investigated by using glass-membrane pH microelectrodes and microsampling techniques. The response of pH microelectrodes was compared to that of a pH macroelectrode system in buffer solutions containing common interfering substances and it was found that the electrodes were insensitive to these substances. Final pancreatic juice electrolyte concentrations and osmolality were found to be similar to that observed by others. Under free-flow conditions, a significant pH gradient was found between small extralobular ducts (7.47) and final juice (8.03). This gradient was nearly obliterated on stimulation with secretin. Duct chloride concentrations were found to be similar in all duct sizes and final juice under unstimulated conditions and after stimulation with secretin. It is concluded that glass-membrane pH microelectrodes are reliable and accurate indicators of pH in this system. The present experiments suggest that the entire extralobular ductal system may participate in the secretion of an alkaline fluid.

Short term nitrogen dynamics in a small Brazilian wetland (Lago Infernão, São Paulo)

1989 ◽  
Vol 5 (3) ◽  
pp. 323-335 ◽  
Author(s):  
Clive Howard-Williams ◽  
F. de Esteves ◽  
J. E. Santos ◽  
M. T. Downes
Keyword(s):  
N Uptake ◽  
Algal Community ◽  
Nitrifying Bacteria ◽  
Temperature Changes ◽  
Time Period ◽  
Uptake Rates ◽  
Eichhornia Azurea ◽  
Short Time ◽  
Epiphyte Community

ABSTRACTWe have studied a number of related processes of the nitrogen cycle in a Brazilian floodplain lake to identify the major pools and pathways over a short time period. The study was centred on the littoral zone dominated by the floating plantEichhornia azurea, which has a large epiphyte algal community of which heterocystous cyanobacteria were the major components. The water column was continuously undersaturated with oxygen although some elevated values (to 60% saturation) were recorded in the macrophyte beds in the afternoon. Marked diel temperature changes were documented. NH4-N dominated the dissolved N component in the water with maximal values (60 mg m−3) at lowest O2, concentrations early in the morning. Nitrogen fixation (acetylene reduction) of the epiphyte community showed marked diel changes with daily values of 5 mg N fixed m−2day−1(based on 3:1 C2H4:N2ratio). Macrophyte NH4-N uptake rates (in situincubations) were 93 mg N m−2day−1. The activities of nitrifying bacteria could not be detected with the nitrapyrin block on dark CO2fixation but denitrification (acetylene block technique) was recorded in the sediments when enhanced with NO-3. The major pathways of aquatic nitrogen involved macrophyte uptake and sediment release of NH4-N.

Respiratory activity, molar growth yields, and ATP content in an Arthrobacter sp. ammonium-limited chemostat culture

1983 ◽  
Vol 29 (9) ◽  
pp. 1136-1140 ◽  
Author(s):  
I. Cacciari ◽  
D. Lippi ◽  
S. Ippoliti ◽  
W. Pietrosanti
Keyword(s):  
Respiratory Activity ◽  
Chemostat Culture ◽  
Morphological Changes ◽  
Sharp Decrease ◽  
Growth Yields ◽  
Atp Content ◽  
Lower Growth ◽  
Wide Range ◽  
Metabolic Activities

Arthrobacter fluorescens was grown in chemostat culture under ammonium-limited conditions and respiratory activity; molar growth yields and ATP content were determined over a wide range of dilution rates. Within a range of dilution rates between 0.10 h−1 and 0.20 h−1, morphological transition occurred, the ratio of cocci to rods appearing inversely related to growth rate. Molar growth yields for both glucose and ammonium decreased with increasing dilution rates because of the higher intracellular polysaccharide content at the lower growth rates. Different metabolic activities were shown in cocci, in rods, and during morphogenesis. A sharp decrease in in situ and potential oxygen quotient (Q(O2)) and in ATP content was observed in the range of dilution rates in which morphological changes occurred.

Stimulation of Nitrate Uptake and Photosynthesis by Molybdenum in Castle Lake, California

1980 ◽  
Vol 37 (4) ◽  
pp. 707-712 ◽  
Author(s):  
R. P. Axler ◽  
R. M. Gersberg ◽  
C. R. Goldman
Keyword(s):  
Nitrate Uptake ◽  
Phytoplankton Community ◽  
Euphotic Zone ◽  
Growing Season ◽  
Uptake Rates ◽  
Early Portion ◽  
Rate Of Photosynthesis ◽  
Castle Lake ◽  
Stimulation Of

The uptake rates of 15NO3 and 14CO2 by the natural phytoplankton community at Castle Lake, California, were measured in situ as responses to 5 μg∙L−1 additions of molybdenum. Stimulation of both nitrate uptake and photosynthesis occurred in water samples containing only relatively high amounts of nitrate. This response to added molybdenum disappeared as the growing season progressed and nitrate was depleted in the euphotic zone. Although molybdenum stimulated nitrate uptake by 55% in water collected from the lower euphotic zone, it did not increase the rate of CO2 uptake because at that depth the rate of photosynthesis was most limited by light intensity and not by nitrogen. An analysis of molybdenum bioassays from 1959 to 1963 is integrated with these findings and points to the importance of molybdenum for phytoplankton growth during the early portion of the growing season when nitrate concentrations in the euphotic zone are maximal.Key words: molybdenum, nitrate, nitrate uptake, micronutrient bioassays

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