The validity of the critical size theory for particles leaving the rumen

1980 ◽  
Vol 94 (2) ◽  
pp. 275-280 ◽  
Author(s):  
D. P. Poppi ◽  
B. W. Norton ◽  
D. J. Minson ◽  
R. E. Hendricksen
Keyword(s):  
Particle Size ◽  
Critical Size ◽  
Compartment Model ◽  
Particulate Material ◽  
Feed Material ◽  
Sieve Size ◽  
Two Compartment Model ◽  
The Mean ◽  
Two Stages

SummaryThree grasses and two legumes, each at two stages of maturity, were fed to three fistulated sheep and samples of the feed, and faeces and contents of the reticulo-rumen, abomasum and ileum were collected for the determination of particle size by wet sieving. Modulus of fineness (MF) was calculated for all particulate matter that failed to pass a 0·15 mm screen. Resistance to flow from the rumen of feed particles of different sizes was also calculated.The mean MF of the reticulo-rumen contents was 2·56 compared with 5·72 for the feed. Material leaving the rumen and found in the abomasum had a MF of 1·67 and subsequent changes were small and not significant; ileum 1·63, faeces 1·80. Particles greater than 1·18 mm passed out of the reticulo-rumen although the quantity was small (1–3%). The resistance to flow of particles of different sizes from the reticulo-rumen was closely related to particle size with no difference between grasses and legumes or between young and mature forages.It was concluded that in modelling the flow of particles from the reticulo-rumen a non-compartmentalized approach should be adopted, but if a simple two-compartment model is required then a critical sieve size of about 1·18 mm may be useful, since less than 5% of the particulate material is retained on this sieve size.

Clearance and Non-Invasive Determination of the Hepatic Extraction of Indocyanine Green in Baboons and Man

1983 ◽  
Vol 64 (2) ◽  
pp. 207-212 ◽  
Author(s):  
S. L. Grainger ◽  
P. W. N. Keeling ◽  
I. M. H. Brown ◽  
J. H. Marigold ◽  
R. P. H. Thompson
Keyword(s):  
Indocyanine Green ◽  
Accurate Determination ◽  
Liver Blood Flow ◽  
Compartment Model ◽  
Hepatic Extraction ◽  
Non Invasive ◽  
Two Compartment Model ◽  
Hepatic Extraction Ratio ◽  
Plasma Disappearance Curve

1. The disposition of an intravenous bolus of indocyanine green (ICG) has been studied in healthy man and baboons using a novel analysis of a two compartment pharmacokinetic model. 2. This analysis enabled the hepatic extraction ratio (ER) of dye to be determined solely from the plasma disappearance curve, and the ER determined did not differ from that measured by hepatic vein catheterization. 3. When compared with clearance measured at steady state, the two compartment model gave a significantly more accurate determination of plasma clearance than did the conventional one compartment model. 4. It is concluded that, in health, liver blood flow may be calculated accurately and noninvasively after a single intravenous injection of ICG.

scholarly journals Serum bactericidal activities and comparative pharmacokinetics of meropenem and imipenem-cilastatin.

1996 ◽  
Vol 40 (1) ◽  
pp. 105-109 ◽  
Author(s):  
M Dreetz ◽  
J Hamacher ◽  
J Eller ◽  
K Borner ◽  
P Koeppe ◽  
...  
Keyword(s):  
Compartment Model ◽  
Pharmacokinetic Parameters ◽  
Time Curve ◽  
Dose Administration ◽  
Microdilution Method ◽  
Two Compartment Model ◽  
Elimination Half ◽  
Renal Clearances ◽  
The Mean ◽  
Bactericidal Activities

The pharmacokinetics and serum bactericidal activities (SBAs) of imipenem and meropenem were investigated in a randomized crossover study. Twelve healthy male volunteers received a constant 30-min infusion of either 1 g of imipenem plus 1 g of cilastatin or 1 g of meropenem. The concentrations of the drugs in serum and urine were determined by bioassay and high-pressure liquid chromatography. Pharmacokinetic parameters were based on an open two-compartment model and a noncompartmental technique. At the end of infusion, the mean concentrations of imipenem and meropenem measured in serum were 61.2 +/- 9.8 and 51.6 +/- 6.5 mg/liter, respectively; urinary recoveries were 48.6% +/- 8.2% and 60.0% +/- 6.5% of the dose in 12 h, respectively; and the areas under the concentration-time curve from time zero to infinity were 96.1 +/- 14.4 and 70.5 +/- 10.3 mg.h/liter, respectively (P < or = 0.02). Imipenem had a mean half-life of 66.7 +/- 10.4 min; that of meropenem was 64.4 +/- 6.9 min. The volumes of distribution at steady state of imipenem and meropenem were 15.3 +/- 3.3 and 18.6 +/- 3.0 liters/70 kg, respectively, and the mean renal clearances per 1.73 m2 were 85.6 +/- 17.6 and 144.6 +/- 26.0 ml/min, respectively. Both antibiotics were well tolerated in this single-dose administration study. The SBAs were measured by the microdilution method of Reller and Stratton (L. B. Reller and C. W. Stratton, J. Infect. Dis. 136:196-204, 1977) against 40 clinically isolated strains. Mean reciprocal bactericidal titers were measured 1 and 6 h after administration. After 1 and 6 h the median SBAs for imipenem and meropenem, were 409 and 34.9 and 97.9 and 5.8, respectively, against Staphylococcus aureus, 19.9 and 4.4 and 19.4 and 4.8, respectively, against Pseudomonas aeruginosa, 34.3 and 2.2 and 232 and 15.5, respectively, against Enterobacter cloacae, and 13.4 and 2.25 and 90.7 and 7.9, respectively, against Proteus mirabilis. Both drugs had rather short biological elimination half-lives and a predominantly renal route of elimination. Both carbapenems revealed high SBAs against clinically important pathogens at 1 h; meropenem had a higher SBA against E. cloacae and P. mirabilis, and the SBA of imipenem against S. aureus was greater than the SBA of meropenem.

The effects of glucose and insulin on contraction of the isolated diaphragm

1977 ◽  
Vol 55 (4) ◽  
pp. 868-881 ◽  
Author(s):  
G. W. Mainwood ◽  
D. Cechetto ◽  
Monique St. Jean
Keyword(s):  
Muscle Fibre ◽  
Isometric Contraction ◽  
Glucose Concentration ◽  
Compartment Model ◽  
Osmotic Gradient ◽  
Model Calculations ◽  
Two Compartment Model ◽  
The Mean ◽  
Effect Of Glucose ◽  
Intracellular Glucose

High glucose concentrations (55 mM) were found to suppress the isometric contraction tension of rat diaphragm. The effect appears to be due to the resulting transmembrane osmotic gradient in spite of the fact that glucose uptake by the diaphragm is fairly rapid. Insulin can reverse the effect of hypertonic glucose to a considerable extent. The problems of estimating intracellular glucose concentration in the isolated muscle are considered. Estimates of intracellular glucose taking into account extracellular space and extracellular diffusion gradients were made using a two-compartment model. Calculations based on the model show that in the presence of insulin, intracellular glucose increases from about 1 to 19 μmol/ml of muscle fibre. The mean transmembrane glucose concentration gradient decreases from 41 to 18 μmol/ml. With the use of the model it appears possible to relate most of the observed effect of glucose and insulin on isometric contraction to their influence on the osmotic gradient across the muscle fibre membrane. Insulin appears to have some additional effects on muscles suppressed by hypertonic solutions which are not accounted for by this mechanism.

Serial determination of glomerular filtration rate in conscious mice using FITC-inulin clearance

2004 ◽  
Vol 286 (3) ◽  
pp. F590-F596 ◽  
Author(s):  
Zhonghua Qi ◽  
Irene Whitt ◽  
Amit Mehta ◽  
Jianping Jin ◽  
Min Zhao ◽  
...  
Keyword(s):  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Compartment Model ◽  
Inulin Clearance ◽  
Male And Female ◽  
Serial Determination ◽  
Two Compartment Model ◽  
Clearance Kinetics

Two nonradioactive methods for determining glomerular filtration rate (GFR) in conscious mice using FITC-labeled inulin (FITC-inulin) were evaluated. The first method measured GFR using clearance kinetics of plasma FITC-inulin after a single bolus injection. Based on a two-compartment model, estimated GFR was 236.69 ± 16.55 and 140.20 ± 22.27 μl/min in male and female C57BL/6J mice, respectively. Total or ⅚ nephrectomy reduced inulin clearance to 0 or 32.80 ± 9.32 μl/min, respectively. Conversely, diabetes mellitus induced by streptozotocin was associated with increased GFR. The other approach measured urinary inulin clearance using intraperitoneal microosmotic pumps to deliver FITC-inulin and metabolic cages to collect timed urine samples. This approach yielded similar GFR values of 211.11 ± 26.56 and 157.36 ± 20.02 μl/min in male and female mice, respectively. These studies demonstrate the feasibility of repeated nonisotopic measurement of inulin clearance in conscious mice.

The relative resistance to escape of leaf and stem particles from the rumen of cattle and sheep

1985 ◽  
Vol 105 (1) ◽  
pp. 9-14 ◽  
Author(s):  
D. P. Poppi ◽  
R. E. Hendricksen ◽  
D. J. Minson
Keyword(s):  
Particle Size ◽  
Animal Species ◽  
Particle Sizes ◽  
Small Particles ◽  
Relative Resistance ◽  
Stages Of Growth ◽  
Two Stages ◽  
Wet Sieving ◽  
Cattle And Sheep

SUMMARYIn a study of the effect of animal species on the threshold particle size leaving the rumen, two grasses cut at two stages of growth and one mature legume were separated into leaf and stem fractions and fed to cattle and sheep. Samples of rumen digesta and faeces were used to determine the validity of using a 1·18 mm porosity screen to separate the rumen particles into large and small pools when studying escape of particles from the rumen. Samples of rumen digesta and faeces were collected for the determination of particle size by wet sieving and the calculation of resistance of particles to passage from the rumen relative to small particles retained on a 0·15 mm sieve.Particles < 1·18 mm but > 0·5 mm had a mean relative resistance to passage of 2·0 and 2·6 for cattle and sheep respectively, compared with resistance values of between 10·9 and 31·2 for particles between 1·18 and 2·36 mm. It is suggested that there is no justification for using different threshold particle sizes for sheep and cattle and that a 1·18 mm sieve may be used to divide the rumen contents of both cattle and sheep into two pools of particles with high and low relative resistance to passage from the rumen.

Is it Possible to Provide a Prognosis after Radical Prostatectomy for Prostate Cancer by Means of a Psa Regression Model?

2005 ◽  
Vol 20 (2) ◽  
pp. 112-118 ◽  
Author(s):  
M. May ◽  
S. Gunia ◽  
C. Helke ◽  
K.P. Braun ◽  
S. Pickenhain ◽  
...  
Keyword(s):  
Radical Prostatectomy ◽  
Computer Program ◽  
Biochemical Recurrence ◽  
Specific Antigen ◽  
Compartment Model ◽  
Recurrence Free Survival ◽  
Free Survival ◽  
Two Compartment Model

Background For over 15 years, studies have been done to evaluate the elimination kinetics of the prostate-specific antigen (PSA) after radical prostatectomy. Even though evaluation of PSA regression in the two-compartment model has become established, no clear data are currently available as to whether a statement can be made with regard to tumor prognosis from a computation of the PSA half-life (PSA-HL). This study focuses on the determination of the PSA-HL in the two-compartment model and on its correlation with the biochemical recurrence-free survival. In addition, a computer program is being developed to simplify the determination of PSA-HL. Material and methods Seventy-seven prospective patients were examined who subsequently had a radical prostatectomy at our facility without neoadjuvant or adjuvant hormone deprivation. In addition to preoperative measurement of the PSA value (d0), PSA determinations were carried out postoperatively on days 5, 10 and 60, and at four-monthly intervals thereafter (mean follow-up: 16 months). By means of the computer program developed for this purpose, CTK. TumW, the PSA half-lives for the first (d0–d5, PSA-HL1) and second (d5–d10, PSA-HL2) compartments were subsequently determined and their effect on biochemical recurrence-free survival was assessed. Results PSA-HL1 and PSA-HL2 were 1.89 (± 0.03) and 3.39 (± 0.14) days, respectively. Whilst PSA-HL1 did not permit any prognostic statement, the median PSA-HL in the second compartment between patients with and without disease progression differed significantly (4.44 versus 3.12 days; p<0.001). Discrimination analysis produced a cutoff of 3.8 days for the second compartment; patients with a PSA-HL2 ≥3.8 days had a significantly worse biochemical recurrence-free survival after 18 months than the other patients (27% versus 93%; p<0.001). Conclusion The PSA regression kinetics after radical prostatectomy follows a two-compartment model in which the prognostic value of the PSA-HL1 is limited. When a cutoff of 3.8 days is used, evaluation of the PSA-HL in compartment 2 (d5–10) appears to permit a prognostic statement. Due to the limited postsurgical follow-up, the disease process was only assessed as biochemical recurrence-free survival, and a longer follow-up will be necessary to generate data on progression-free survival.

The Accurate Gasometric Determination of the Oxygen-Hemoglobin Equilibrium in Dilute Solutions of Sheep Hemoglobin

1963 ◽  
Vol 9 (6) ◽  
pp. 682-709 ◽  
Author(s):  
F JW Roughton
Keyword(s):  
Intermediate Compound ◽  
Equilibrium Curve ◽  
Dilute Solutions ◽  
Kinetic Information ◽  
Equilibrium Data ◽  
The Mean ◽  
Comparison Of The Results ◽  
Two Stages ◽  
Sheep Hemoglobin

Abstract Apparatus and technique are described for the accurate gasometric macrodetermination of the oxygen-hemoglobin equilibrium in dilute solutions containing around 0.15 gm. Hb/100 ml., equivalent to blood diluted 100:1. At the bottom of the equilibrium curve, i.e., in the range 0-2% Hb02, the method is accurate to ± 0.05% HbO2. Over the main part of the curve the mean accuracy is ± 0.5% Hb02. From such data, together with indirect kinetic information as to the character of the extreme top of the equilibrium curve, it has been possible, in the case of dilute sheep Hb solutions, to compute all four constants in Adair's general intermediate compound equation for the equilibrium between oxygen and hemoglobin. Comparison of the results at pH 7.1 and 9.1 suggests that the first two oxygen molecules combine independently at both pH's. Interaction sets in at the third and more markedly at the fourth stage, but there are detailed differences in the degrees of interaction at these last two stages at the two pH's. It is hoped that these equilibrium data in dilute sheep Hb solution will be of service in interpreting kinetic experiments on the rates of the reactions of oxygen and hemoglobin, which so far can only be carried out in dilute solutions of the latter.

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