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Blood circulation plays an important role in the thermal regulation of the human body, particulaly in the periphery. In this study, the mechanism of thermal regulation in the middle human finger has been numerically investigated. A two-dimensional thermal model of the human finger, which consists of skin, tendon, bone, main arteries, and veins, has been developed. The tissue temperatures are obtained by solving the basic bioheat equation using a finite difference scheme. The arterial and venous temperatures, as well as blood perfusion rate are computed by the one-dimensional thermo-fluid model of blood circulation in the upper limb. The geometry of the human finger is obtained from the measurement. The profiles of blood pressure, blood flow rate, and temperatures in the arteries, veins, and tissues are obtained. Simutaneously, the temporal variation of the skin temperature in the hand before and after exercise was measured using thermography in order to verify the periodic characteristic of blood temperature in the periphery. Spectrum analysis of the temperature was carried out. A weak periodic variation was observed in the skin temperature near the blood vessels due to the heart beat when blood flow increased, which corroborated the result simulated by the model.

Scientists use the SAR (specific absorption rate) to determine the amount of radiation that human tissue absorbs. This measurement is especially important for mobile telephones, which radiate close to the brain. The model studies how a human head absorbs a radiated wave from an antenna and the temperature increase that the absorbed radiation causes. In view of the effects of electromagnetic radiation to human body, the influence of surrounding environment caused by EM radiation is always a serious problem. Also, parameters called body loss and perfusion rate are defined.

Aims: To assess inter- and intra-study reproducibility of myocardial contrast echocardiography (MCE) imaging for quantitative measurement of myocardial perfusion rate in humans in ambulatory setting. Methods and results: In 20 subjects, we performed 2 MCE tests 20–40 min apart on the same day under the same standardized protocol, and evaluated single-reader between-study and between-reading reproducibility of assessment of indicators of myocardial perfusion rate, such as the slope of video-intensity change k , and the factors A (peak video-intensity) and B (background video-intensity after bubble destruction) and the product k × A . The region of interest was placed at the mid-posterior interventricular septal wall visualized in apical 4-chamber view. In a sub-analysis, we evaluated indicators of myocardial perfusion rate comparing subjects with normal vs. those with subnormal ejection fraction (EF). Inter-study reproducibility of assessment of k was relatively low (intraclass correlation coefficient = 0.36), whereas intra-study reproducibility was fair (intraclass correlation coefficient = 0.61). The parameters k × A and B showed higher reproducibility than the k (inter- and intra-study intraclass correlation coefficients 0.64 and 0.75, 0.74 and 0.91, respectively). For reference, reproducibility data of the depth of the region of interest, of EF and CO were excellent. k and k × A were lower in subjects with low vs. those with normal EF. Only k and k × A were lower in subjects with subnormal than in those with normal EF. Conclusions: The MCE-derived indicator of myocardial perfusion rate k × A showed fairly good between-study and between-reading reproducibility.

The experimental research and heat transfer calculation of dog's tongue was processed on the basis of Traditional Chinese Medicine (TCM). Firstly, the blood perfusion rate of dog tongue was measured by the method of invasive. Secondly, the two-dimensional temperature fields of specific cross-section of tongue were calculated by the finite element method. Lastly, some conclusions were drawn, that inside the tongue body the blood perfusion change can make blood vessel to expand or constrict, and affect surface temperature field of tongue, on the other hand, the tongue cross-section temperature distribution is chiefly affected by the artery, blood vessel area and location. The above researches were carried out in order to seek the major factor that affects the tongue surface temperature distribution, and try to explain the relationship between tongue temperature and “tongue color”, which is a very important concept in Tongue Inspection of TCM, and if tongue surface temperature distribution can reflect the state of “tongue color” indirectly, these calculation results can help to analyze heat transfer characteristic of organism. In addition, the research method can be used to calculate the two-dimensional temperature field in various blood perfusion rate and multi-blood vessels affection.

Desmethylimipramine (DMI), an α2-adrenergic antagonist, is a nearly ideal deposition tracer for evaluating the myocardial flow distribution with the least artifactual effects on microcirculation. Myocardial retentions of tritium- and iodine-125-labeled DMI (HDMI, IDMI) were confirmed to be satisfactory; the retentions of IDMI and HDMI at 1 min were 95 and 91% respectively in isolated Tyrode-perfused rabbit hearts (n=6) at a perfusion rate of 8.1 ml/min/g, and 98 and 96% respectively, in blood-perfused rat hearts (n=4) at a perfusion rate of 3.1 ml/min/g. Using these tracers combined with subtraction digitalradiography, it allowed the assessing of changes of myocardial flow distribution with 400×400 μ m 2 resolution. In blood-perfused rat hearts (n=4), the validity of this method was verified by the strong cross-correlation between regional densities of two tracers injected simultaneously (r=0.94) and the regression line having a slope close to one. Furthermore, in Tyrode-perfused rabbit hearts, the flow distributions were evaluated before and after decreasing perfusion rate moderately by 34% (n=7) and severely by 70% (n=7). Severe flow reduction increased the coefficient of variation of tracer density (CV) significantly from 19 to 25%, but CV did not change with moderate flow reduction (20 vs. 19%). Regional densities of two tracers were cross-correlated still substantially under severe low-flow perfusion (r=0.84). Accordingly, flow differences between originally high- and low-flow regions were enlarged under severe flow reduction. In conclusion, double-tracer digitalradiography based on the DMI deposition will be a potent method for the analysis of flow heterogeneity at microvascular levels.

The effect of perfusion on the temperature distribution during radio-frequency hyperthermia and laser-induced thermotherapy was investigated with the perfused porcine kidney model. The phase shift-based proton resonance frequency shift method was used to map the temperature distribution. In experiments with modulated perfusion rates it was demonstrated that perfusion dissipates a significant amount of the absorbed energy and, therefore, the resulting heat distribution is strongly dependent on the perfusion rate. The measured time course of the temperature distribution was used to estimate the thermal conductivity, local perfusivity and heat absorption rate of the tissue. These parameters were in a good agreement with literature data. This approach can also be extended to measure heat absorption and heat transfer parameters in vivo, which can significantly improve the accuracy of thermotherapy session planning.

The aim of this study was to develop a physiologically based pharmacokinetic (PB-PK) model capable of describing and predicting terbinafine concentrations in plasma and tissues in rats and humans. A PB-PK model consisting of 12 tissue and 2 blood compartments was developed using concentration-time data for tissues from rats ( n = 33) after intravenous bolus administration of terbinafine (6 mg/kg of body weight). It was assumed that all tissues except skin and testis tissues were well-stirred compartments with perfusion rate limitations. The uptake of terbinafine into skin and testis tissues was described by a PB-PK model which incorporates a membrane permeability rate limitation. The concentration-time data for terbinafine in human plasma and tissues were predicted by use of a scaled-up PB-PK model, which took oral absorption into consideration. The predictions obtained from the global PB-PK model for the concentration-time profile of terbinafine in human plasma and tissues were in close agreement with the observed concentration data for rats. The scaled-up PB-PK model provided an excellent prediction of published terbinafine concentration-time data obtained after the administration of single and multiple oral doses in humans. The estimated volume of distribution at steady state ( V ss ) obtained from the PB-PK model agreed with the reported value of 11 liters/kg. The apparent volume of distribution of terbinafine in skin and adipose tissues accounted for 41 and 52%, respectively, of the V ss for humans, indicating that uptake into and redistribution from these tissues dominate the pharmacokinetic profile of terbinafine. The PB-PK model developed in this study was capable of accurately predicting the plasma and tissue terbinafine concentrations in both rats and humans and provides insight into the physiological factors that determine terbinafine disposition.

A closed-form analytical solution of the Pennes bio-heat equation was developed for the temperature distribution in skin tissue subjected to a constant surface heat flux. Elevations in the surface temperature were revealed to be related to blood perfusion rates and heating fluxes based on which a new noninvasive approach has been developed to determine the blood perfusion rates. Sensitivities of the temperature elevation to blood perfusion and heating flux were investigated, as was the influence of thermal contact resistance on the perfusion estimate. It has been demonstrated that this influence is relatively small and can be effectively eliminated by application of highly conductive grease. An experimental system for this method was developed, and the blood perfusion rates in various human locations, including forearm, thigh, and calf, were measured using the system. The blood perfusion rate of skin tissue is in the range of 4 to 6 kg⋅s−1⋅m−3, which is in good agreement with those reported in the literature.

A high-accuracy microdialysis method that can provide the reference values of glucose concentration in interstitial fluid for the accurate evaluation of non-invasive and minimally invasive continuous glucose monitoring is reported in this study. The parameters of the microdialysis process were firstly optimized by testing and analyzing three main factors that impact microdialysis recovery, including the perfusion rate, temperature, and glucose concentration in the area surrounding the microdialysis probe. The precision of the optimized microdialysis method was then determined in a simulation system that was designed and established in this study to simulate variations in continuous glucose concentration in the human body. Finally, the microdialysis method was tested for in vivo interstitial glucose concentration measurement.

Thermal infrared imaging has been proposed, and is now used, as a tool for the non-contact and non-invasive computational assessment of human autonomic nervous activity and psychophysiological states. Thanks to a new generation of high sensitivity infrared thermal detectors and the development of computational models of the autonomic control of the facial cutaneous temperature, several autonomic variables can be computed through thermal infrared imaging, including localized blood perfusion rate, cardiac pulse rate, breath rate, sudomotor and stress responses. In fact, all of these parameters impact on the control of the cutaneous temperature. The physiological information obtained through this approach, could then be used to infer about a variety of psychophysiological or emotional states, as proved by the increasing number of psychophysiology or neurosciences studies that use thermal infrared imaging. This paper presents a review of the principal achievements of thermal infrared imaging in computational psychophysiology, focusing on the capability of the technique for providing ubiquitous and unwired monitoring of psychophysiological activity and affective states. It also presents a summary on the modern, up-to-date infrared sensors technology.

There is currently a shift in Bioprocessing towards continuous manufacturing of monoclonal antibodies or recombinant proteins in perfusion mammalian cell cultures (Konstantinov & Cooney, Journal of Pharmaceutical Sciences, 2015). A cell retention device is the key technology component that enables the shift to continuous production. A novel acoustic cell retention device operates by continuously drawing off a harvest flow, equal to the perfusion rate of the bioreactor, while recirculating the retained cells back to the bioreactor. The harvest flow path is tangent and significantly smaller than the recirculation rate. The device utilizes a novel acoustophoretic effect known as an “acoustic edge/interface” effect in conjunction with a recirculating flow beneath the acoustic harvest chamber which collects and returns cells to the bioreactor. This interface effect operates by creating a radiation pressure/force field at the interface between cell-free harvest and cell-laden circulating fluids. Numerical resul...

Intracerebral microdialysis is an increasingly popular experimental technique. A brief description of the principles of microdialysis is presented and the terms relevant to the procedure are defined. The methodology involved in conducting intracerebral microdialysis is described in detail. Factors influencing the outcome of analysis such as external stimuli, perfusion fluid, perfusion rate, temperature, probe placement, membrane characteristics, and timing of sample collection are discussed. The importance of maintaining the uniformity of the above-mentioned factors is stressed.

Radiofrequency ablation is a medical procedure used to treat a variety of illnesses including liver carcinomas that cannot be treated by resection or radiological procedures. A multi-physics code was used to solve the Bio-heat Equation by a finite element methodology. The volume of coagulation necrosis caused by the heating of the tumor tissue as a function of perfusion rate was determined. A multi-needle probe deposited the RF energy into the tissue. Once the tissue was heated to greater than 50°C it was considered irreversibly damaged. Increasing perfusion rates reduced the size of the lesion. In order to heat a volume to a required temperature the time elapsed did increase.Copyright © 2013 by ASME

A non-damage method for measuring local tissue blood perfusion rate by surface heat disturbance and its two special embodiments for realizing this measurement are presented in this paper. In the derivation of mathematical model, the Pennes equation is used, and two parameters which are very difficult to be known - the arterial blood temperatureTa and the metabolic heat generation rateqm, have been eliminated. So it has provided a feasible basis for application. In this paper, the performance and the adaptable condition of the measurement method and its structure peculiarities are discussed over a wide variety of parameters. Moreover, the effectiveness of the measurement method has been demonstrated by means of the quantitative measurement of tissue in vitro, the comparative measurement of animal under artificial perfusion and the dependence measurement in human body.

Reliable methods based on MRI for measurement of the perfusion rate in human tumors are highly warranted. Tumors of two amelanotic human melanoma xenograft lines were subjected to dynamic 1H MRI after i.v. administration of gadopentetate dimeglumine (Gd-DTPA). The aim was to investigate to what extent different perfusion parameters determined from the Gd-DTPA kinetics, i.e., the initial uptake rate, the maximal uptake, the decay rate, and the perfusion rate calculated by use of the Kety equation, can be used as a reliable estimate of tumor perfusion rate. Each parameter was calculated in dual; one calculation was based on relative signal intensity increase (RSII) in T1-weighted MR images and the other on Gd-DTPA concentration determined from the images. The perfusion parameters were compared with the perfusion rates determined from measurement of tumor uptake of 86Rb or [14C]iodoantipyrine. The results showed that reliable estimates of tumor perfusion rate can be achieved from analysis of Gd-DTPA kinetics by use of the Kety equation. Gd-DTPA kinetics based on concentration might be used to achieve reliable estimates of absolute tumor perfusion rate, whereas reliable estimates of the relative perfusion rate might also be achieved from Gd-DTPA kinetics based on RSII. The initial uptake rate, the maximal uptake, and the decay rate of Gd-DTPA, however, are not reliable estimates of tumor perfusion rate, mainly because these parameters are highly influenced by the tumor extracellular volume fraction in addition to the perfusion rate.

An immortalised mouse hepatocyte line was grown in culture flasks and in a small-scale fixed-bed system to determine growth characteristics and a suitable carrier type. The cells were then cultivated in a 40 ml fixed-bed reactor over 75 days at a perfusion rate of 6.25 ml medium per ml fixed-bed and day. A cell density of approx. 8.5.107 cells per ml carrier was reached at the end of the experiment proving that a stable cultivation was possible over a long period of time with constant consumption and production rates.

Four iridoid glycosides isolated from different species of Eremophila (Myoporaceae) were tested for their effects on the Langendorff rat heart. Melampyroside (1), verminoside (2), ferruloylajugol (3) and catalpol (4) all significantly decreased contractile force in the isolated rat heart test. Within a minute after administration all, except catalpol, significantly increased heart rate and coronary perfusion rate. These results are compared to those of other cardioactive iridoid glycosides described in the literature.

A new, simple and fast method for the determination of the interaction parameters of sulfamethoxazole (SMZ) to human serum albumin (HSA) has been developed by utilizing a microdialysis sampling technique combined with liquid chromatography (LC). The drug and protein were mixed in different molar ratios in 0.067 M potassium phosphate buffer, pH 7.4, and incubated at 37 °C in a water-bath. Then the microdialysis probe was put in the SMZ-HSA solution and sampled at a perfusion rate of 1 μl/min. The concentration of SMZ in the microdialysates was determined by reversed-phase liquid chromatography. The recovery ( R ) was also determined in vitro under similar conditions, R is about 41.8% with an RSD of about 2.3%. The association constant ( K ) and the number of the binding sites on one HSA molecule ( n ) are calculated by three equations, the values of nK estimated by three methods are quite similar. The values found for K and n are 3.24 × 10 3 M −1 and 3.04, respectively.

Application of femtosecond lasers to cataract surgery has added unprecedented precision and reproducibility but ocular safety limits for the procedure are not well-quantified. We present an analysis of safety during laser cataract surgery considering scanned patterns, reduced blood perfusion, and light scattering on residual bubbles formed during laser cutting. Experimental results for continuous-wave 1030 nm irradiation of the retina in rabbits are used to calibrate damage threshold temperatures and perfusion rate for our computational model of ocular heating. Using conservative estimates for each safety factor, we compute the limits of the laser settings for cataract surgery that optimize procedure speed within the limits of retinal safety.

According to the requirement of the calibration in minimally invasive blood glucose monitoring, a method based on microdialysis was presented to monitor glucose level in interstitial fluid continuously. An experimental system simulating the continuous change of glucose concentration in vivo was built. The influences on recovery of microdialysis caused by flow rate, glucose concentration, and temperature etc. were studied. The results led to the conclusion that the recovery fell by 71.7% when perfusion rate increased from 0.3 μL/min to 3.0 μL/min, while the different concentrations of glucose solutions scarcely contribute to the recovery instead, and the temperatures from 25 to 58 °C caused the recovery to increase by 34.6%.

This paper presents development of a microwave system for noninvasive blood perfusion measurement. The proposed system is based on a thermal perfusion measuring method using microwave techniques. In this method, the tissue temperature is raised by microwave heating (900 MHz) to no more than one degree Celsius, and after the discontinuation of the microwave heating signal, the temperature decay measured using microwave radiometric sensing (1-2 GHz) is indicative of the blood perfusion rate. The preliminary results of the system's test are provided.

Introduction: Microdialysis is one of the methods used clinically for the detection of ischemia. Although microdialysis is reliable, in most clinical settings there is a delay of 1-2 hours before the information is available. Objective: The aim of this study was to evaluate whether an increase in the Microdialysis per fusion rate from 0.3 to 1.0 or 2.0 μl/min was capable of reducing the delay in the detection of a shift in molecular composition. Methods and material: Microdialysis was performed in a container with 3 catheters per fused with 0.3, 1.0 and 2.0 μl/min. The molecular composition in the container regarding glucose and lactate was initially as follows: CGlucose=6.0 mmol/L and CLactate=2 mmol/L. At T=90 min the composition was changed to CGlucose=1 mmol/L and CLactate=12 mmol/L. Dialysates were harvested from the three catheters and were analysed regarding the concentration of glucose and lactate. For calculation of the relative recovery, samples were harvested directly from the liquid. The relative recovery and the delay before new steady state were calculated for each of the 3 catheters. The experiment was performed 8 times. Results: A decrease in relative recovery was found with the higher perfusion rate. For glucose, the relative recovery was 100, 88, and 69% at perfusion rates of 0.3, 1.0 and 2.0 μl/min. For lactate, the corresponding values were 103, 93, and 77%. An increase in the lactate/glucose ratio was found with the higher perfusion rate. The delays in detection of shift in molecular concentration were found to be 60, 20, and 10 minutes for catheters 0.3, 1.0 and 2.0, respectively. Conclusion: Using microdialysis it is possible to significantly reduce the delay while still detecting a shift in the concentration of glucose and lactate when the perfusionrate is increased.

The isolation and identification of two cardioactive compounds from two Eremophila species (Myoporaceae) considered important in the pharmacopoeia of the Australian Aboriginal people is described. Verbascoside, isolated from the methanol and water extracts of E. alternifolia leaves, mediated significant increases in chronotropism, inotropism and coronary perfusion rate (CPR) in the Langendorff rat heart. Geniposidic acid, isolated from the methanol extract of E. longifolia leaves, mediated an inhibitory effect with significant negative chronotropism, negative inotropism and CPR.

A non-damage method for measuring local tissue blood perfusion rate by surface heat disturbance and its two special embodiments for realizing this measurement are presented in this paper. In the derivation of mathematical model, the Pennes equation is used, and two parameters which are very difficult to be known - the arterial blood temperatureTa and the metabolic heat generation rateqm, have been eliminated. So it has provided a feasible basis for application. In this paper, the performance and the adaptable condition of the measurement method and its structure peculiarities are discussed over a wide variety of parameters. Moreover, the effectiveness of the measurement method has been demonstrated by means of the quantitative measurement of tissue in vitro, the comparative measurement of animal under artificial perfusion and the dependence measurement in human body.

This paper presents an analysis of heat sink effect in hepatic cancer treatment near arterial vessel for microwave ablation by using finite element method. We analyze the temperature distribution, Specific Absorbtion Rate (SAR) and coagulation area in two models. The first is hepatic tissue without artery and the second is hepatic tissue with artery. In the second model, we specify distance between antenna and artery at 10 mm. The initial condition is set as power at 50 watts, temperature at 37 °C and blood perfusion rate is varied at 6.4 × 10-10, 6.4 × 10-3 and 6.4 × 104 l/s. The simulation results by using three-dimensional finite element analysis show that the temperature distribution in case of hepatic tissue with no artery is larger than the case with artery. We also found that blood perfusion rate affects to the temperature distribution in hepatic tissue. Higher blood perfusion rate, higher heat sink effect occur.

Purpose: The novel thermo-brachytherapy (TB) seed provides a simple means of adding hyperthermia to LDR prostate permanent implant brachytherapy. The high blood perfusion rate (BPR) within the prostate motivates the use of the ferrite and conductive outer layer design for the seed cores. We describe the results of computational analyses of the thermal properties of this ferrite-based TB seed in modelled patient-specific anatomy, as well as studies of the interseed and scatter (ISA) effect. Methods: The anatomies (including the thermophysical properties of the main tissue types) and seed distributions of 6 prostate patients who had been treated with LDR brachytherapy seeds were modelled in the finite element analysis software COMSOL, using ferrite-based TB and additional hyperthermia-only (HT-only) seeds. The resulting temperature distributions were compared to those computed for patient-specific seed distributions, but in uniform anatomy with a constant blood perfusion rate. The ISA effect was quantified in the Monte Carlo software package MCNP5. Results: Compared with temperature distributions calculated in modelled uniform tissue, temperature distributions in the patient-specific anatomy were higher and more heterogeneous. Moreover, the maximum temperature to the rectal wall was typically ∼1 °C greater for patient-specific anatomy than for uniform anatomy. The ISA effect of the TB and HT-only seeds caused a reduction in D90 similar to that found for previously-investigated NiCu-based seeds, but of a slightly smaller magnitude. Conclusion: The differences between temperature distributions computed for uniform and patient-specific anatomy for ferrite-based seeds are significant enough that heterogeneous anatomy should be considered. Both types of modelling indicate that ferrite-based seeds provide sufficiently high and uniform hyperthermia to the prostate, without excessively heating surrounding tissues. The ISA effect of these seeds is slightly less than that for the previously-presented NiCu-based seeds.

To help define the optimal conditions for the preparation of vascular corrosion casts of rat heart, we examined the effect of prefixation with aldehyde fixatives on the perfusion rates of rat heart and on the quality of vascular casts. For these studies, beating hearts were removed from rats, cannulated via the aortic stump, arrested with KCl, perfused retrograde with buffered saline or fixative, and infused with resin to prepare corrosion casts. Fixatives used were 2.5% glutaraldehyde or 2% paraformaldehyde, and the casting resin consisted of a Mercox-methylmethacrylate mixture (4:1). All perfusion pressures were monitored at 80 to 100 mm Hg using a mercury manometer. The perfusion rate of control hearts was 13 to 14 mL/min. Prefixation with glutaraldehyde and paraformaldehyde reduced perfusion to 8.5 and 8.1 mL/min, respectively. Cast quality was observed grossly and with the scanning electron microscope. Control hearts yielded high quality, complete casts with 2570 capillaries/mm(2+). Casts from prefixed hearts exhibited areas of incomplete vessel filling and resisted complete tissue maceration, leaving tissue remnants adhering to the vessel replicas. Casts from glutaraldehyde-fixed hearts were of very poor quality. Our results indicate that prefixation is an unnecessary step in the preparation of vascular casts of rat heart and is inconsistent with cast quality.

Modeling bioheat transfer plays an important role in the treatment planning of cancer therapy. Historically, Pennes bioheat equation has been used for bioheat transfer modeling in living tissue because of its simplicity, effectiveness and ease of application. It is imperative that the effect of each parameter involved in the bioheat transfer be known. The ultimate goal of a cancer treatment is to maximize the damage to the cancer affected tissue and minimize the collateral damage to the normal tissue surrounding it. This study takes into account six 3-level factors namely blood perfusion rate in healthy tissue and tumor, frequency, applied voltage, metabolic heating rate in healthy tissue and tumor. The purpose of this study is to rank the parameters involved in electromagnetic heating and determine the factors which affect the bioheat transfer the most. Maximum obtained temperature was taken as the response variable and Taguchi orthogonal arrays were used to obtain required data with minimum number of numerical experiments required. Calculations were performed in Minitab statistical software. The results show that the applied voltage has the largest effect on the maximum achieved temperature followed by frequency of the electromagnetic radiation.

Perfusion culture is a commonly used dynamic culture technique in tissue engineering for promoting higher cell number growth. Under perfusion culture, the cell number could be co-influenced by cell detachment and cell proliferation. However, previous studies have mainly focused on the perfusion effects on cell proliferation but largely ignored the aspect of cell detachment. This work demonstrates that perfusion as small as 2.3 mL/min have induced cell loss compared with static culture even for a culture period of 12 minutes Both perfusion rate and direction have influenced the cell retention in the construct. In general, higher perfusion rates have caused more cell loss, largely due to the induced higher flow shear. The influence of perfusion directions on cell retention has been closely related to cell distribution in the construct. The study shows that cell retention is an important aspect that is worth more research attention and should be considered for cell number analysis in 3D construct development. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 101A: 647–652, 2013.

To test the hypothesis that the distribution of hemodynamic resistance is involved in the control of pulmonary capillary surface area, we measured permeability-surface area product (PS) and longitudinal resistance distribution (LRD) as functions of perfusion rate in isolated rabbit lungs under zone II conditions (n = 10) and through the zone II-III transition (n = 4). PS, considered to be indicative of functioning capillary surface area, was measured with the aid of the diffusion-limited tracer [14C]propanediol, whereas LRD was determined using a viscous bolus technique. LRD was seen to change character with increasing flow and increasing PS/surface area, becoming bimodal with low central resistance as full capillary recruitment was approached in zone III. Effects of hypoxic ventilation were studied in zone II in five lungs; it was found that hypoxia altered the LRD and eradicated the normoxic dependence of PS/surface area on perfusion rate. It was concluded that LRD is involved in the determination of functioning capillary surface area.

The contribution of the loop segments to lithium reabsorption in sodium-replete, anesthetized Sprague-Dawley rats was examined by perfusing superficial loops of Henle between late proximal convolutions and early distal tubules. Preliminary experiments in which lithium was initially present only inside or outside the perfused loop confirmed substantial permeability of one or more of the loop segments to lithium. In subsequent experiments, in which lithium was infused intravenously and included in the perfusate so that the perfusate-to-plasma lithium concentration ratio was close to that found in late proximal tubules during lithium clearance studies, lithium reabsorption was inversely related to the perfusion rate: values for fractional lithium reabsorption (FRLi) at perfusion rates of 10, 20, and 30 nl/min were 58 +/- 3, 17 +/- 2, and 2 +/- 2%, respectively. Bumetanide (10(-6) M) markedly inhibited FRLi but also reduced water reabsorption, suggesting an effect on the pars recta at this dose; 10(-7) M bumetanide, which was without effect on water reabsorption, had only a small effect on FRLi at a perfusion rate of 10 nl/min but reduced FRLi by approximately 70% at 20 nl/min. We argue that the remarkable flow dependency of lithium reabsorption, together with its bumetanide sensitivity, provides evidence for significant voltage-driven lithium reabsorption in the thick ascending limb of Henle.

schnermann makes several strong points in his article “Adenosine mediates tubuloglomerular feedback responses” ([19][1]). We completely agree that the data provided by two independent laboratories demonstrating that tubuloglomerular feedback (TGF) responses to increases in distal perfusion rate

Temperature is a very important factor in laser moxibustion. This paper foucus on temperature field in simulated living-porcine liver tissue radiated by laser. Firstly, we place simulated blood vessels in isolated porcine liver to simulate living liver and obtain simulation temperature field by the finite element analysis; then we use K type thermocouples and thermocouple amplifier respectively measured the temperature field of isolated porcine liver and simulated living liver. The experiment results of the two are basically consistent, in the same position of organization, blood perfusion rate will be significantly lower the temperature. These researches provide the basis for the establishment of laser moxibustion in TCM.

A NS0 cell line was used for the production of monoclonal antibody using a perfusion process based on spin filter technology. The process involves a batch phase followed by perfusion for building up the cell counts. The duration of the perfusion phase is usually restricted by the clogging of the spin filter. Perfusion rate was found to be a very important factor influencing the performance of the spin filter. Higher perfusion rates resulted in higher cell loss from the bioreactor and early clogging of the filter. The loss of cells also resulted in switching of the cells to growth phase which lowered the cell productivity. This observation was confirmed by using other perfusion devices like hollow fiber cartridges and perfusion wave bags which allow complete cell retention and hence increase cell productivity. Medium screening program resulted in finding a medium which gave more than double the cell count with half the perfusion rate of the original process. A further improvement by the spent medium analysis with supplementation of deficient medium components and perfusion rates optimization also resulted in a significant increase in IgG titre. With the new process there was a three-fold increase in the total product per day from the bioreactor and from the increase in cell count.

This paper presents a pumpless cell culture chip, where a constant-rate medium perfusion is achieved by balanced droplet dispensing. Previous pumpless cell culture chips, where the gravity-driven flow is induced by gradually decreasing the hydraulic-head difference, Δh, between source and drain reservoirs, result in a decreasing perfusion-rate. However, the present pumpless cell culture chip, where autonomous droplet dispensers are integrated on the source reservoirs, results in a constant perfusion-rate using a constant Δh maintained by balanced droplet dispensing between the source-inlet and the drain-outlet. In the experimental study, constant perfusion-rates of 0.1, 0.2, and 0.3 μl min(-1) are obtained by Δh of 38, 76, and 114 mm, respectively. At the constant perfusion-rate (Q=0.2 μl min(-1)), H358 lung cancer cells show the maximum growth-rate of 57.8 ± 21.1% d(-1), which is 1.9 times higher than the 30.2 ± 10.3% d(-1) of the static culture. At a perfusion-rate varying between 0.1-0.3 μl min(-1) (average=0.2 μl min(-1)), however, the H358 cells show a growth-rate of 46.9 ± 8.3% d(-1), which is lower than that of the constant Q of 0.2 μl min(-1). The constant-rate perfusion culture (Q=0.1, 0.2, and 0.3 μl min(-1)) also results in an average cell viability of 89.2%, which is higher than 75.9% of the static culture. This pumpless cell culture chip offers a favorable environment to cells with a high growth-rate and viability, thus having potential for use in cell-based bio-assays.

Modeling and monitoring of blood perfusion in burn skin has been presented in this study. A non invasive Laser speckle contrast imaging (LSCI) system is presented here for monitoring different flow conditions in a burn layer simulated capillary phantom. Speckle contrast variations with respect to changes in burn depth and blood perfusion rate have been studied in this work.

In the past ten years, one has seen rapid advancements in heat and mass transport applications in biology and medicine. The research activities have been shifted from fundamental development of better theoretical models accurately describing the thermal effect of local vasculature geometry and blood perfusion rate in the 1980s and 1990s to emphases on biotransport research with clear clinical applications and on how to utilize theoretical simulation and imaging techniques for better designing treatment protocols in those applications. This review will first describe briefly technical advancements in bioheat and mass transfer in the past several decades and then focus on two important applications in bioheat and mass transport covering different temperature ranges: hypothermia in brain injury and hyperthermia in tissue thermal damage. The contributions of nanotechnology, imaging tools, and multiscale modeling to the advancements will be discussed in the review.

A perfusion-based high cell density (HD) cell banking process has been developed that offers substantial advantages in time savings and simplification of upstream unit operations. HD cell banking provides the means to reduce the time required for culture inoculum expansion and scale-up by eliminating the need for multiple small to intermediate scale shake flask-based operations saving up to 9 days of operation during large-scale inoculum expansion. HD perfusion cultures were developed and optimized in a disposable Wave bioreactor system. Through optimization of perfusion rate, rocking speed and aeration rate, the perfusion system supported peak cell densities of >20 × 10(6) cells/mL while maintaining high cell viability (≥ 90%). The cells were frozen at HD (90-100 × 10(6) viable cells/mL) in 5-mL CryoTube vials. HD cell banks were demonstrated to enable direct inoculation of culture into a Wave bioreactor in the inoculum expansion train thus eliminating the need for intermediate shake flask expansion unit operations. The simplicity of the disposable perfusion system and high quality of the cell banks resulted in the successful implementation in a 2000 L scale manufacturing facility.

For metabolic diseases, functional changes are often earlier than structural lesions, for example, diabetes. The paper aims to provide a survey using Support Vector Machine (SVM) to predict and assess metabolic functions of diabetes based on bio-heat transfer theory and infrared thermal imaging technology. Two metabolic characteristic values, metabolic function parameter and blood perfusion rate, are extracted from thermography data of cold water stimulation experiment as inputs of SVM to set up models by different kernel functions. For more than 2000 clinical data used in the paper, the prediction accuracy averaged 90%. The research provides a new attempt to evaluate diabetes metabolic function, hoping for contribution to early detection of diabetes.

There has been considerable interest in developing sound and accurate thermal models that describe heat transfer within a living tissue with blood perfusion. Since the landmark paper by Pennes (1948), a number of bioheat transfer equations for living tissue have been proposed to remedy possible shortcomings in his equation. Although Pennes’ model is often adequate for roughly describing the effect of blood flow on the tissue temperature, there exist some serious shortcomings in his model due to its inherent simplicity, as pointed out by Wulff (1974), namely, assuming uniform perfusion rate without accounting for blood flow direction, neglecting the important anatomical features of the circulatory network system such as countercurrent arrangement of the system, and choosing only the venous blood stream as the fluid stream equilibrated with the tissue.

Thermal imaging is an emerging method for early detection of female breast tumor. The main challenge for thermal imaging used in breast clinics lies in how to detect or locate the tumor and obtain its related parameters. The purpose of this study is to apply an improved method which combined a genetic algorithm with finite element thermal analysis to determine the breast tumor and its parameters, such as the size, location, metabolic heat generation and blood perfusion rate. A finite element model for breast embedded a tumor was used to investigate the temperature distribution, and then the influences of tumor metabolic heat generation, tumor location and tumor size on the temperature were studied by use of an improved genetic algorithm. The results show that thermal imaging is a potential and effective detection tool for early breast tumor, and thermal simulation may be helpful for the explanation of breast thermograms.

Perfusion processes provide high volumetric productivity by retaining a large cell number in a relatively small size bioreactor. The increased cell concentration however, often requires enormous perfusion rates which in turn lead to low product concentrations. Additionally the resulting large volumes cause problems in downstream processing. In this study IgG producing CHO cells were cultivated on Cytopore 1 and Cytoline 1 in a stirred tank reactor and a fluidised bed reactor respectively. Both microcarrier cultivations were run as perfusion processes over 50 days. The resulting volumetric productivities and antibody concentrations were compared to cultivation in batch and fedbatch culture. The composition of the culture medium was optimised to limit perfusion rate and hence increase product concentration.

The activity and characteristics of tubuloglomerular feedback (TGF) are altered subsequent to reductions in renal mass or blockade of the renin-angiotensin system. This study assessed the combined effects of renal ablation and captopril on TGF. Renal mass was reduced in male Sprague-Dawley rats by the surgical removal of 1 1/2 kidneys. At 2 and 8 wk postsurgery, TGF was studied by micropuncture before and after the administration of captopril (0.5 mg/kg i.v.) Before captopril, TGF in remnant kidneys (NX) was characterized by a higher tubular perfusion rate required for a 50% maximal response (TGF turning point) as compared with intact kidneys of controls (CNT) at both 2 (NX, 35 +/- 3; CNT, = 19 +/- 1 nL/min; P less than 0.05) and 8 wk (NX, 54 +/- 5; CNT, 20 +/- 1 nL/min; P less than 0.05). Captopril significantly increased the turning point in both intact and remnant kidneys at both 2 (NX, 43 +/- 2; CNT, 25 +/- 2 nL/min) and 8 wk (NX, 61 +/- 5; CNT, 28 +/- 2 nL/min) postsurgery. Captopril also significantly reduced the maximal TGF response in both intact and remnant kidneys at 2 (NX from 13 +/- 3 to 7 +/- 1 mm Hg; CNT from 10 +/- 1 to 5 +/- 1 mm Hg) and 8 wk (NX from 15 +/- 1 to 9 +/- 2 mm Hg; CNT from 13 +/- 1 to 7 +/- 1 mm Hg).(ABSTRACT TRUNCATED AT 250 WORDS)

Given a styrene tissue/blood partition coefficient of ca. 39 and a relatively low perfusion rate of ca. 0.03 ml/min-g tissue, adipose tissue provides a useful physiologically damped integrative measure of environmental exposure. Styrene in the adipose tissue of nonoccupationally exposed individuals was measured for the first time. Tissue samples obtained from elective surgery patients and postmortem donors were analyzed by capillary gas chromatography and found to contain 1.12 +/- 1.06 (mean +/- SD) ppm styrene. Using these measured tissue levels and an apparent clearance of styrene (defined as the ratio of blood clearance to adipose tissue/blood partition coefficient), environmental intake of styrene was estimated to be 2.23 mg/hr, corresponding to an inhaled concentration of 1.96 mg/m3 (476 ppb). This value is two to three orders of magnitude higher than typical breathing zone air measurements, indicating additional undiscovered sources of styrene exposure.

A skin burn model using variable thermophysical properties as a function of water content is studied as it is subjected to a heat flux at the skin surface. The model employs the finite element method to solve Pennes' [1] bio-heat equation as it is subjected to heat fluxes modeled from actual sensor test data. The model assesses burn damage using the burn integral of Henriques [2] using burn-threshold criteria Ω at both the epidermal-dermal and dermal-subcutaneous tissue interface. The model's times-to-degree burn, cumulative burn damage Ω, and peak temperatures are studied as the blood perfusion rate and water contents for the respective layers of skin are separately and arbitrarily varied. Results from the variable- and constant-property Pennes' models are compared.

Using micro-fabrication techniques a micro thermal probe has been developed in our laboratory to measure the thermal conductivity of biological tissues. This paper presents our latest experimental results which demonstrate the usefulness of the micro thermal probe in mapping the complicated perfusion field inside biological tissues. A perfused pig liver model has been constructed to simulate in vivo conditions. The portal vein and hepatic artery of a porcine liver were intubated and connected to a perfusion circuit. Saline water was perfused through the liver driven by a peristaltic pump. By varying the pumping rate of the perfused model, we measured the effective thermal conductivity at different perfusion rates in different locations. The results show that the effective thermal conductivity varies with the square root of the perfusion rate. Also, by rotating the micro probes, we observed a strong directional dependence of the effective thermal conductivity, revealing that perfusion is not a scalar but a vector field.