scholarly journals The diffusion capsule, a novel device for the addition of a solute at a constant rate to a liquid medium. Its application to metabolic regulation

1971 ◽  
Vol 121 (2) ◽  
pp. 293-297 ◽  
Author(s):  
S. J. Pirt
Keyword(s):  
Metabolic Regulation ◽  
Diffusion Theory ◽  
Culture Technique ◽  
Shake Flask Culture ◽  
Concentrated Solutions ◽  
Permeable Membrane ◽  
Novel Device ◽  
Constant Rate ◽  
Substrate Diffusion ◽  
Micro Organisms

The diffusion capsule consists of a cylindrical container that can be completely filled with a solution and sealed with a small semi-permeable membrane at one end. In use, the capsule is immersed in an agitated liquid. Experiments on concentrated solutions in the capsule showed that, contrary to diffusion theory, the rate of diffusion of solute (sugars or amino acids) out of the capsule remained virtually constant until about 65% of the solute had diffused out of the capsule. Thus the device has been used to maintain constant material feed rates for periods exceeding 30h. The capsule is a simple and compact substitute for a pump and is superior to a pump for small feed rates in many applications. The capsule greatly extends the scope of the shake-flask culture technique for micro-organisms in that substrate-limited growth, possibly the aspect of greatest interest, is readily achieved simply by dropping in the flask a capsule containing the substrate. Diffusion feed should facilitate study of the metabolism of toxic substrates: also it is likely to provide an improved means for supplying a pulse of tracer to a culture.

scholarly journals ON THE PERMEABILITY OF THE STOMACH MUCOSA FOR ACIDS AND SOME OTHER SUBSTANCES

1939 ◽  
Vol 23 (2) ◽  
pp. 263-274 ◽  
Author(s):  
Torsten Teorell
Keyword(s):  
Gastric Juice ◽  
Stomach Content ◽  
Diffusion Theory ◽  
Weak Acids ◽  
Permeable Membrane ◽  
Alkali Ions ◽  
Stomach Mucosa ◽  
Other Substances ◽  
Concentration Changes ◽  
Alkali Chlorides

1. Solutions approximately isotonic with blood of strong and weak acids, several salts, glucose, and glycine were introduced in the resting stomachs of cats. The concentration and volume changes were recorded. 2. It was found that the stomach mucosa was permeable to the majority of the ions tested. There was also a permeability in the opposite direction from the blood (mucosa) to the stomach content, particularly of alkali chlorides. Poorly permeable substances were glucose, glycine, and sodium iodate. Pure weak acids such as acetic acid penetrated very rapidly. 3. The electrolyte concentration changes in the stomach content (or gastric juice) are pictured as an exchange diffusion; for instance, the hydrogen ions of an acid are exchanged against alkali ions of the mucosa or blood. 4. It is pointed out that the concept of the mucosa as an ion permeable membrane could be used as the foundation of a "diffusion theory," which can explain the acidity and chloride variations of the gastric juice without postulating neutralizing or diluting secretions.

scholarly journals Effect of different levels of phosphorus on rumen microbial fermentation and synthesis determined using a continuous culture technique

1987 ◽  
Vol 57 (2) ◽  
pp. 279-290 ◽  
Author(s):  
Sylvie Komisarczuk ◽  
R. J. Merry ◽  
A. B. McAllan
Keyword(s):  
Continuous Culture ◽  
Volatile Fatty Acids ◽  
Rumen Fluid ◽  
Artificial Saliva ◽  
Inorganic Phosphorus ◽  
Ammonia Nitrogen ◽  
Culture Technique ◽  
Phosphorus Requirements ◽  
Micro Organisms

1. A continuous culture technique was used to study the phosphorus requirements of rumen micro-organisms. Solutions of artificial saliva containing 120, 80, 40 and 0 mg inorganic phosphorus (Pi)/1 were infused into the reaction vessels previously inoculated with rumen contents, resulting in Piconcentrations in the vessel contents of 48, 28, 4 and < 1 mg/l respectively. Various fermentative and synthetic characteristics were examined.2. In the vessel contents, concentrations of protozoa (about 0.9 x 105/ml) were not significantly affected by piconcentration. Total volatile fatty acids (VFA) produced averaged about 6.83 mmol/h with Pilevels of 48 and 28 mg/l. Reduction in Piconcentrations to 4 and < 1 mg/l resulted in significant reductions in total VFA to approximately 6.25 and 3.75 mmol/h respectively, accompanied by a rise in pH from 6.5 to 7.3. Ammonia-nitrogen values, which averaged about 131 mg/l at the higher Piconcentrations, also increased with the lowest level of Pito about 240 mg/l. ATP concentrations averaged about 14 μmol/l at the highest Piconcentration and fell progressively with each reduction in Piconcentration to a final value of 2.5μmol/1 with the Pilevel < 1 mg/1.3. At Piconcentrations of 48 and 28 mg/l, the digestibilities of xylose, arabinose and cellulose-glucose were maintained at about 0.90, 0.62 and 0.70 g/g input respectively. At lower Pi, concentrations these digestibilities fell significantly and corresponding values at Pi< 1 mg/l were 0.73, 0.41 and 0.31 respectively. Starch digestion was unaffected by Piconcentrations and remained at about 0.90 g/g input.4. The amount of microbial-N synthesized averaged 0.48 g/d and was maintained with Piconcentrations down to 4 mg/l. There was, however, a significant reduction to 0.26 g/d with Piconcentrations of < l mg/l. The effiency of microbial protein synthesis was variable but averaged approximately 25 g N/kg total carbothdrate fermented.5. It was estimated that the minimum Piconcentrations required in rumen fluid in vivo to maintain maximum degradative and synthetic microbial activities was in the range 75–100 mg/l and that the over-all P requirement of the microbes was of the order of 5.1 g/kg apparently digested organic matter intake.

Side-chain degradation of certain ω-phenoxyalkanecarboxylic acids by Nocardia coeliaca and other micro-organisms isolated from soil

1962 ◽  
Vol 156 (963) ◽  
pp. 172-186 ◽  
Keyword(s):  
Fatty Acids ◽  
Sole Carbon Source ◽  
Oxidation Mechanism ◽  
Caproic Acid ◽  
Culture Technique ◽  
Garden Soil ◽  
Side Chain ◽  
Wheat Coleoptile ◽  
Chain Lengths ◽  
Micro Organisms

Five micro-organisms were isolated from a garden soil by a selective culture technique in which ϵ -(2:4:5-trichlorophenoxy) caproic acid was used as sole carbon source. The capacity of these organisms to degrade the side-chain of certain ω -plienoxyalkanecarboxylic acids C 6 H 5 O(CH 2 ) n COOH was then determined using chromatographic methods for the separation of the products of metabolism. Three of the organisms, viz. Nocardia coeliaca, Pseudo­monas sp. and Micrococcus sp. were found to effect side-chain breakdown readily. All the subsequent investigations here reported were carried out with N. coeliaca. Ten ω -phenoxyalkanecarboxylic acid homologues were incubated with this organism and the chromato­graphic pattern was shown to be consistent with β -oxidation, some hindrance being apparent with shorter chain lengths. In addition, with those homologues containing 9 and 10 methy­lene groups, there was evidence of another type of breakdown which could arise from an α -oxidation mechanism which Stumpf has shown to operate with fatty acids of a certain chain length. Phenol was not detected in metabolized solutions of any of the phenoxy homologues. The cells of the organism, however, which had been incubated with the pro­pionic, valeric or heptanoic acids ( n = 2, 4 or 6), i. e. those acids theoretically able to yield phenol by β -oxidation, were found to have an increased capacity for metabolizing phenol. It was therefore concluded that phenol is, in fact, produced in the metabolism of these phenoxy acids by N. coeliaca. Metabolism experiments were also carried out with members of six homologous series of chloro-substituted phenoxyalkanecarboxylic acids. The corresponding phenol was estimated in solutions after metabolism in each case and the results were readily explicable in terms of β -oxidation of the side-chain. The breakdown patterns on chromatograms were also typical of this type 'of oxidation. Certain types of ring substitution were shown to hinder β -oxidation in a manner to that found in our earlier investigations in which wheat coleoptile and pea stem tissues were used.

Curves formed by colonies of micro-organisms growing on a plane surface

1945 ◽  
Vol 35 ◽  
pp. 14-19 ◽  
Author(s):  
Agnes H. Waddell
Keyword(s):  
Single Cell ◽  
Solid Medium ◽  
Plane Surface ◽  
Two Dimensional ◽  
Present Discussion ◽  
Whole Process ◽  
First Approximation ◽  
Constant Rate ◽  
Expanding Circle ◽  
Micro Organisms

In many cases, when a colony of micro-organisms such as moulds, yeasts or bacteria grows on the plane surface of a solid medium (e.g.agar), starting from a single cell, the colony tends to grow as an ever expanding circle. The reason for this is that every cell, if free from competition, can multiply at roughly a constant rate in all directions in a plane, limited by the fact that territory occupied by one cell cannot be occupied by another. For the purposes of the present discussion, we can assume, as a first approximation, that the whole process is two-dimensional.

Hydrogel-swelling driven delivery device for corrosion resistance of metal in water

2015 ◽  
Vol 72 (12) ◽  
pp. 2270-2276 ◽  
Author(s):  
Yu Gu ◽  
Li-Ming Yang ◽  
Jie Chen ◽  
Ling-Ling Wang ◽  
Bin Chen
Keyword(s):  
Weight Loss ◽  
Corrosion Resistance ◽  
Water System ◽  
Carbon Steels ◽  
Delivery Device ◽  
Permeable Membrane ◽  
Constant Rate ◽  
Release Property ◽  
Hydrogel Swelling ◽  
Loss Experiment

Corrosion on steel and copper pipes in industry can trigger pollution and weakness due to undesired chemical and biochemical reactions. Too much or too little inhibitor can decrease its efficiency, even causing waste and pollution. In this contribution, an innovative delivery device driven by hydrogel swelling, mainly consisting of a semi-permeable membrane, a hydrogel-swelling force drive and a release orifice, was developed to control the release of inhibitor in a water system at a constant rate, leading the amount of inhibitor to maintain a proper concentration. The effects of hydrogel mass and orifice dimension on release property were studied for controlling release rate. Moreover, a weight loss experiment on carbon steels was carried out to show the incredible anti-corrosion function of the system.

Review of the Radiation Damage Problem of Organic Specimens in Electron Microscopy

1973 ◽  
Vol 31 ◽  
pp. 476-477
Author(s):  
L. Reimer
Keyword(s):  
Electron Microscopy ◽  
Radiation Damage ◽  
Irradiation Time ◽  
Dose Effect ◽  
Primary Process ◽  
Thin Specimen ◽  
Secondary Damage ◽  
Small Doses ◽  
Micro Organisms ◽  
Damage Processes

Most information about a specimen is obtained by elastic scattering of electrons, but one cannot avoid inelastic scattering and therefore radiation damage by ionisation as a primary process of damage. This damage is a dose effect, being proportional to the product of lectron current density j and the irradiation time t in Coul.cm−2 as long as there is a negligible heating of the specimen.Therefore one has to determine the dose needed to produce secondary damage processes, which can be measured quantitatively by a chemical or physical effect in the thin specimen. The survival of micro-organisms or the decrease of photoconductivity and cathodoluminescence are such effects needing very small doses (see table).

Constant-Rate Feed Device. A Reply to Comment

1950 ◽  
Vol 22 (7) ◽  
pp. 956-956 ◽  
Author(s):  
Lester Lundsted
Keyword(s):  
Constant Rate ◽  
Feed Device
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