Percentage Clearance Research Articles

Albumin Clearance from Human Skeletal Muscle During Prolonged Steady‐State Running

This study was designed to find out if the lymph flow, indicated as albumin clearance, from active skeletal muscle is maintained constant during a prolonged steady-state exercise. 99mTc-labelled albumin was injected bilaterally into the vastus lateralis muscles of eight endurance-trained men. The radioactivity at the injection site was monitored by a gamma-camera before, frequently during, and after a 2 h run at a controlled steady intensity of 69 +/- 4% of the maximal heart rate. The fractional clearance rate of albumin was calculated for each monitoring interval, and was expressed as percentage clearance per minute (% min(-1)). During the first 15 min of exercise the clearance rate was five times higher than at rest before the exercise (0.29 +/- 0.12 vs. 0.06 +/- 0.05% min(-1), P = 0.001). During the next 25 min of running the clearance rate fell to 0.19 +/- 0.08% min(-1) (P = 0.02), from which level it was further attenuated, being 0.12 +/- 0.04% min(-1) at the end of the exercise. After the exercise the clearance rate fell rapidly to the level of 0.04 +/- 0.03% min(-1). The results showed that the albumin clearance from working muscles is not constant during steady-state exercise, suggesting that lymph flow from exercising skeletal muscle may not be constant despite lymphatic pumping being assumed to be unchanged during the course of exercise (i.e. constant exercise intensity and running speed).

Prediction of recurrent choledocholithiasis by quantitative cholescintigraphy in patients after endoscopic sphincterotomy

Background—Endoscopic sphincterotomy (EST) is widely used for the removal of stones from the bile duct, but stones recur in about one fifth of patients.Aims—To investigate hepatic clearance by quantitative cholescintigraphy...

Airway and alveolar permeability and surface liquid thickness: theory.

The thickness of airway surface liquid (ASL) can be calculated as the ratio of the permeability coefficient of an absorbed inert tracer to the percentage rate in which it decreases in content in the airway lumen. The percentage clearance of radiolabeled diethylenetriaminepentaacetic acid (DTPA) from human airways or lungs has been measured many times, with a mean value of 1.04 +/- 0.25 (SD) %/min. Rates of clearance from animal lungs of most species give values of the same order, although they are lower in the sheep and higher in the dog. Permeability coefficients have not been measured simultaneously with percentage clearances and not at all for human tissues. Values for mannitol and sucrose, of which the former gives a permeability coefficient approximately 25% greater than that for sucrose and DTPA in airway tubes and isolated mucosal sheets from experimental animals, give a mean approximately 7.1 x 10(-7) cm/s. This corresponds to thickness of ASl of approximately 20-150 microns for various species. The assumptions underlying this estimate are discussed. It is concluded that ASL thickness in vivo may be considerably greater than in vitro measurements involving rapid freezing of the airway wall. Estimates of alveolar permeability suggest that either it is very considerably lower than that of the airway epithelium, that methods to measure alveolar permeability mainly reflect airway permeability, or both.

99Tcm-HMPAO and 99Tcm-DTPA radioaerosol clearance measurements in idiopathic pulmonary fibrosis

The clearance rate of an inhaled aerosol of a lipophilic complex, 99Tcm-hexamethylpropyleneamine oxime (99Tcm-HMPAO), was compared with that of a hydrophilic complex, 99Tcm-diethylenetriamine pentaacetate (99Tcm-DTPA), in nine normal subjects and in eight patients with idiopathic pulmonary fibrosis (IPF). Data were acquired as follows. The subjects were placed supine with their back against the scintillation camera and breathed aerosol for 2 min; pulmonary radioactivity was then monitored for 30 min. A time-activity curve (TAC) was generated from the region of interest (ROI) over the periphery of each lung field and a computer program was then used to calculate percentage clearance per minute (k) in each lung. The mean (+/- S.E.M.) rate of clearance of 99Tcm-DTPA (k = 1.31 +/- 0.13% min-1) was not significantly different from that of 99Tcm-HMPAO (k = 1.32 +/- 0.27% min-1, P > 0.025) in the normal subjects. However, 99Tcm-DTPA clearance was 1.91 +/- 0.27% min-1 and 99Tcm-HMPAO clearance 0.78 +/- 0.17% min-1 in eight patients with IPF (P < 0.001, 99Tcm-DTPA vs 99Tcm-HMPAO). By regression analysis using a multiplicative model, both values correlated fairly [r = -0.71, y = exp (0.08-0.85 ln chi); P < 0.005], with a change in clearance rate in the opposite direction in all eight patients. The results of our study demonstrate that the pulmonary clearance of 99Tcm-HMPAO is different from that of 99Tcm-DTPA in IPF.

Kupffer cell and hepatocyte function in rat transplanted liver.

The liver consists essentially of two compartments, parenchymal cells (PC) and non parenchymal cells (NPC) i. e. Kupffer cells, endothelial cells, fat storing cells and pit cells. PC remain after transplantation but NPC are eventually exchanged with host cells. Dynamic liver scintigraphy with albumin colloid, extracted by NPC, and IODIDA, extracted by PC, were tested to evaluate function as determined by clearance rates in these two cellular compartments. Experimental liver transplantation was performed in 15 syngeneic rats. Following transplantation, we performed dynamic liver scintigraphy with 0.5 ml 5 MBq 99mTc-Nanocoll and 0.5 ml 20 MBq 99mTc-IODIDA, 10 s per frame, 30 min for each examination. Percentage clearance rate, per minute was calculated from uptake curves over the liver. Uptake curves were nearly exponential and clearance rates could be estimated from a logarithmic plot of uptake versus time. The clearance rate was 25 +/- 4% per min (mean +/- SD) for NPC and 32 +/- 15% per min for PC in controls. After liver transplantation it was 31 +/- 7% per min for NPC and 30 +/- 15% per min for PC. Dynamic liver scintigraphy with 99mTc-Nanocoll and 99mTc-IODIDA alloweds a separate assessment of the function of PC and NPC after experimental liver transplantation in rats.

Asonic Imaging for Extracorporeal Shockwave Lithotripsy: Analysis of Factors in Successful Treatment

The emergence of real-time ultrasonic imaging for extracorporeal shockwave lithotripsy poses questions regarding the factors and techniques which facilitate stone imaging for clinicians with no previous practical experience in ultrasonography. The ability of these clinicians to assess when stone disintegration has been achieved also needs to be confirmed. A wide range of data was recorded from each of 2688 lithotripsy treatments performed over a 2-year period using the EDAP LT.01 ultrasound-imaged piezoelectric lithotriptor. An analysis of these data was performed using a comprehensive microcomputer-based statistics package. The mean time taken for stone imaging and positioning was reduced from 11.2 to 7.5 min over the 2-year period. Obese patients and those with renal pelvic stones were best imaged in a lateral position. Overall there was no difference in percentage stone disintegration or clearance between treatments in the supine or lateral positions, but a significant reduction in the clearance of small caliceal stones resulted when the lateral position was used. Factors associated with a significantly greater percentage of stone disintegration and clearance included pain experienced by the patient during fine adjustment of the processing head during treatment, acoustic focus attenuation and widening and acoustic shadow widening as detected by the urologist at the end of treatment. Among the factors not associated with significant alterations in the percentage of stone disintegration or clearance were the lithotriptor operator, the side or site of the calculus, obesity and shockwave frequency or power. This study confirmed the ability of urologists to develop expertise in ultrasonography for renal stone imaging and to interpret successfully the subtle signs of stone disintegration.

Cumulative Effects of Repeated Surfactant Treatments in the Rabbit

The responses of the adult rabbit lung to multiple doses of surfactant after intratracheal injections of either natural calf surfactant or Surfactant-TA were evaluated. For each surfactant, four groups of 1.4-kg rabbits were studied: group 1 received 100 mg of surfactant containing isotopically-labeled dipalmitoylphosphatidylcholine; group 2 received the same labeled surfactant and then three tracheal injections of vehicle; group 3 received labeled surfactant and then three doses (100 mg) of unlabeled surfactant; group 4 was treated in the same way as group 3 except that the final dose was of the labeled surfactant. All rabbits were killed, and alveolar washes were recovered 24 h after the labeled surfactant dose had been given. The amount of labeled palmitate-saturated phosphatidylcholine (Sat PC) in alveolar washes did not change after multiple doses of calf surfactant, indicating that subsequent doses did not alter the clearance of previous doses. The four doses of calf surfactant increased the alveolar Sat PC pool size by a factor of 2.5 only when measured 6 h after the last dose, but the total lung Sat PC pool size doubled, indicating a loss of most of the surfactant Sat PC to the lung tissue. In contrast, Surfactant-TA increased the alveolar pool size by a factor of 4 after the single dose and by a factor of 11 after the multiple doses, and the percentage clearance of labeled Sat PC from the lungs decreased with multiple doses, indicating an effect of subsequent doses on the initial dose. The quantity of Sat PC cleared from the lungs increased by about a factor of 2 after the multiple doses of Surfactant-TA. Although repetitive surfactant doses changed alveolar and lung Sat PC pool sizes the quantity of Sat PC cleared from the lungs increased, and the lungs accommodated the large amount of surfactant without short-term adverse effects.

Investigation into the effect of Fenoterol on mucociliary clearance in patients with chronic bronchitis.

We investigated the effect of Fenoterol, a selective beta 2 adrenoceptor stimulant, on mucociliary clearance in 12 patients with chronic bronchitis. Mucociliary clearance was measured with a scintillation camera after inhalation of a 99mTc labelled aerosol. Fenoterol was administered one h after acquisition commenced and imaging was maintained for a further two h. Three regions of interest (ROI) were selected over each lung to generate time activity curves. Corrections for decay, alveolar deposition (using 24 h image), cough and movement of activity through each ROI were carried out. An exponential function was fitted to the clearance curves to determine clearance rates. The increase in percentage clearance after Fenoterol administration for the left and right whole lung ROI was 35% and 36% per h respectively (P = 0.006 and 0.020). Fenoterol enhances cilial clearance in chronic bronchitis patients.

Effect of copper deficiency on the lymphatic absorption of cholesterol, plasma chylomicron clearance, and postheparin lipase activities.

The lymphatic absorption of cholesterol and plasma clearance of chylomicrons were investigated in Cu-deficient rats (CuD) fed 0.5 mg Cu/kg diet, as compared with Cu-adequate control rats (CuA) fed 7.5 mg/kg diet. Cholesterol absorption was measured by the 14C-radioactivity appearing in the mesenteric lymph at hourly intervals for 8 hr after an intraduodenal dose of [14C]cholesterol. The plasma clearance of chylomicrons was measured at 3, 6, and 10 min after an intravenous dose of chylomicrons labeled in vivo with [3H]retinyl ester. Cumulative [14C]cholesterol absorption and total lymphatic output of cholesterol were significantly decreased in CuD at 4 hr and thereafter, with no change in percentage distribution of free and esterified cholesterol. Over an 8-hr period, 7.3% of the dose was absorbed by CuD and 9.2% by CuA. When [3H]chylomicrons, obtained from a CuD or CuA donor rat, were injected into CuD and CuA recipient rats, the label was cleared faster in CuD during the first 3 min. At 6 and 10 min, however, no significant difference in percentage clearance of the dose was observed between the groups. The half-life (t1/2) of [3H]chylomicrons and the total 3H-radioactivity taken up by the liver during the entire 10-min period did not differ between the groups, regardless of the source of chylomicrons. The activities of both endothelial lipoprotein lipase (LPL) and hepatic lipase (HL) in postheparin plasma were markedly lower in CuD. As expressed in micromoles fatty acid released/hr/ml plasma, the activities of LPL in CuD and CuA were 32.6 +/- 1.9 and 45.6 +/- 1.3, respectively. A similar magnitude of difference was also observed in HL activity. The data provide evidence that copper deficiency impairs the intestinal transport of cholesterol and the peripheral lipolysis of chylomicrons. The data, however, strongly suggest that the hepatic uptake of chylomicron remnants via the apo-E-dependent mechanism may not be impaired in Cu deficiency.

On the prediction of impact noise, Part IX: The noise from punch presses

The punch press is a further classical example of impact noise: the force is built up in the punch relatively slowly, and the whole machine is strained until the load on the material being punched reaches a yield and shortly afterwards a fracture level. At this stage the strain energy in the machine and its workpiece must be redistributed and this leads to vibration of the whole machine and to noise radiation. In this paper work which has been carried out at ISVR over a number of years is presented. It describes the way the Energy Accountancy Equation [1] can be modified to relate the noise radiated directly to the sum of the squares of the large rates of change of force against time, and illustrates clearly the way that noise control, with use of passive or active methods in designing the punch tooling, can be related directly to the one parameter 10 log Σ[ f( t)] max 2. It is shown that noise levels can be reduced by up to 30 dB under ideal conditions by fracture pulse tailoring while still cutting metal, but that more realistically, 10 dB reductions may be obtained below those of current practice by practical tool design. An explanation is given of why large open presses are never likely to achieve the proposed factory noise levels and that the noise from double-sided presses can be controlled effectively by tooling modifications and by the addition of damping. The paper describes work carried out on passive and active cancellation systems used to arrest and springback of the press structure following workpiece material fracture and explains the practical limitations of such systems. Active techniques are limited by the difficulties obtained, with brittle hard materials, of finding a trigger and load freezing system which can operate fast enough to reduce adequately the force parameter 10 log Σ ( f max( t)) 2. Where punching finish allows, it has been found that well-designed shear and/or cutting with low percentage clearance is superior to active cancellation, since this provides a surer method of reducing the above force parameter, especially for harder materials. The Energy Accountancy Equation suggests that the use of increased structural damping can be an effective method of noise reduction, particularly if the punch press structure is initially only lightly damped. Experiments on a third-scale model of a 200 tonne double-sided press suggest that this damping needs to be added selectively in areas where the vibrational energy density is high and coincides with areas of high noise radiation. Thus, in the experiments described, 12 dB reduction has been obtained under such conditions, only 1 or 2 dB reduction being obtained when damping of the base plate has been unaltered.

Evaluation of Thompson's buried dermal flap operation for lymphoedema of the limbs: A clinical and radioisotopic study

SEARCH for an operation which will improve the lymphatic drainage from a lymphlogged limb continues. The buried dermal flap operation (Thompson, 1962, 1964, 1965) has been claimed to be a physiological operation on the assumption that anastomosis of the superficial lymphatics of the dermis and the lymphatics of the deeper compartment occurs, and also that lymphovenous communications develop between the transposed superficial lymphatics and the venules of the deeper compartment. This thesis is reasonable but so far no conclusive evidence has been. presented to show that these assumptions are correct. Thompson (1967) claimed that lymphatic drainage improves significantly after operation because of the more rapid clearance of Ii3’ tagged human serum albumin (RIHSA) from lymphoedematous upper limbs in 4 out of 5 patients. He also reported in a IO-year survey of 79 patients so treated “good” and “satisfactory” results in 92 per cent of cases of primary lymphoedema, in all cases (author’s italics) of secondary lymphoedema of the lower limb and in 94 per cent of the upper limbs treated (Thompson, 1970); In view of such impressive results, my interest was aroused and I have carried out the buried dermal strip operation in 5 cases of secondary lymphoedema of the leg. The follow-up period is up to 2 years and the results have been evaluated by direct circumferential measurement and RIHSA clearance. For the RIHSA clearance test 1-2~ Ci RIHSA was injected in the diseased leg and counting was done immediately after injection on a gamma scintillation counter (medical spectrometer) with a No. I, thallium activated crystal of 2 in diameter and ri in thickness, the probe having been placed over the site of injection and touching the skin. The standard was also counted simultaneously. Counting was done daily until the clearance reached above 90 per cent, the first reading of the counts at the time of injection having been taken as 0.0 per cent clearance. All the readings were corrected for natural decay and background. The percentage clearance of RIHSA in 24 hours, and the time in hours taken for 50 per cent clearance (T&) were then calculated.

Change in respiratory waveform did not produce any remarkable alteration in rate and item of nitrogen elimination in any subject Furthermore, use of different respiratory wave forms did not significantly alter pulmonary nitrogen clearance delay percentage or lung clearance index (indices of uniformity of inhpulmonary gas mixing)

Change in respiratory waveform did not produce any remarkable alteration in rate and item of nitrogen elimination in any subject Furthermore, use of different respiratory wave forms did not significantly alter pulmonary nitrogen clearance delay percentage or lung clearance index (indices of uniformity of inhpulmonary gas mixing)