Continuous plankton records stand the test of time: evaluation of flow rates, clogging and the continuity of the CPR time-series

The Continuous Plankton Recorder (CPR) survey is one of themost extensive biological time-series in existence and has beenin operation over major regions of the North Atlantic since1932. However, there is little information about the volumeof water filtered through each sample, but rather a generalassumption has persisted that each sample represents 3 m³. Datafrom electromagnetic flowmeters, deployed on CPRs between 1995and 1998, was examined. The mean volume filtered through sampleswas 3.11 m³ and the effect of clogging on filtration efficiencieswas not great. Consequently, even when the likely variationsin flow due to clogging are taken into account, previously identifiedlinks between zooplankton abundance and climatic signals remainstrong.     

Vortex flow filtration of mammalian and insect cells

The use of vortex flow filtration for harvesting cells or conditioned medium from large scale bioreactors has proven to be an efficient, low shear method of cell concentration and conditioned medium clarification. Several 8–10 L batches of the human histiocytic lymphoma U-937 cell line (ATCC CRL 1593) were concentrated to less than 1 L by vortex flow filtration through a 3.0 m membrane. An aggressive filtration regimen caused a 17% loss of cell viability and a 32% loss of IL-4 receptor binding capacity when compared to a batch centrifuged control. A reduction of the rotor speed from 1500 to 500 RPM and reduction of system back pressure from 10 to 0 PSIG resulted in cell viability and IL-4 binding capacity comparable to the control. Several 10 L batches of baculovirus infected Sf-9 cells were also concentrated to less than 1 L by vortex flow filtration through a 3.0 m membrane. SDS-PAGE analysis of filtrate samples showed that aggressive filtration caused cell damage which led to contamination of the process stream by cellular lysate. When rotor speed was reduced to 500 RPM and system back pressure was reduced to 0 PSIG, the amount of contaminating lysate proteins in filtrate samples was comparable to a batch centrifuged control.     

Bronchial vascular contribution to lung lymph flow

The lymphatic vessels of thelung provide an important route for clearance of interstitial edemafluid filtered from pulmonary blood vessels. However, the importance oflung lymphatics for the removal of airway liquid filtered from thesystemic circulation of the lung has not been demonstrated. We studiedthe contribution of the bronchial vasculature to lung lymph flow inanesthetized, ventilated sheep (n = 35). With the bronchial artery cannulated and perfused (control flow = 0.6 ml · min¹ · kg¹),lymph flow from the efferent duct of the caudal mediastinal lymph nodewas measured 1) during increasedbronchial vascular perfusion (300% of control flow);2) with a hydrated interstitium induced by a 1-h period of left atrial hypertension and subsequent recovery, both with and without bronchial perfusion; and3) during infusion (directly intothe bronchial artery) of bradykinin, an inflammatory mediator known tocause changes in bronchial vascular permeability. Increased bronchialperfusion for 90 min resulted in an average 35% increase in lung lymphflow. During left atrial hypertension, the increase in lung lymph flowwas significantly greater with bronchial perfusion (339% increase overbaseline) than without bronchial perfusion (138% increase).Furthermore, recovery after left atrial hypertension was more completeafter 90 min without bronchial perfusion (91%) than with bronchialperfusion (63%). Infusion of bradykinin into the bronchial arteryresulted in a prompt and prolonged 107% increase in lung lymph flow.This was not seen if the same dose was infused into the pulmonaryartery. Thus bronchial vascular transudate contributes significantly to lymph flow from the efferent duct of the caudal mediastinal lymph node.These results demonstrate that lymph vessels clear excess fluid fromthe airway wall and should be considered when evaluating the effect ofvascular leak in airway obstruction.

     

Submarine groundwater discharge in Osaka Bay, Japan

Submarine groundwater discharge (SGD) rates in Osaka Bay were continuously measured and analyzed to evaluate seawater–groundwater interactions. Fast Fourier transfer and power spectrum density methods were applied to analyze the dominant periods of the SGD variations. Diurnal and semidiurnal periods of SGD variation were found, and they were caused by tidal effects. According to the separation of SGD into fresh and recirculated water components using automated seepage meter measurements and terrestrial groundwater flow analyses, the fresh groundwater component in SGD was evaluated to be in the range 4%–29% at Tannowa, Osaka. Therefore, SGD rates depend mainly on the volume of recirculated seawater. Correlation analyses between SGD and sea level show that SGD is delayed by 4h after sea level changes.     

Transpiration measurements on apple trees with an improved stem heat balance method

Since the late eighties a handy and user-friendly sap flow meter (Dynagage®) is on the market which can quantify 0205 the sap flow through intact plant stems, based on the stem heat balance method. The documentation about its accuracy and reliability, however, is still too limited to use it as a standard method in field experiments with apple trees. We therefore tested this commercial system on potted apple trees (Malus domestica L.; cv. Red Elstar and Jonagold; on rootstock M9 vf) with stem diameters of 1.8 to 4 cm. The measured sap flow was compared with mass loss measured by an automated balance, supposing the total mass loss of the trees was equal to the water loss by transpiration. The results revealed three major problems:

Mechanisms of blood flow during pneumatic vest cardiopulmonary resuscitation

Mechanisms of blood flow during cardiopulmonary resuscitation (CPR) were studied in a canine model with implanted mitral and aortic flow probes and by use of cineangiography. Intrathoracic pressure (ITP) fluctuations were induced by a circumferential pneumatic vest, with and without simultaneous ventilation, and by use of positive-pressure ventilation alone. Vascular volume and compression rate were altered with each CPR mode. Antegrade mitral flow was interpreted as left ventricular (LV) inflow, and antegrade aortic flow was interpreted as LV outflow. The pneumatic vest was expected to elevate ITP uniformly and thus produce simultaneous LV inflow and LV outflow throughout compression. This pattern, the passive conduit of "thoracic pump" physiology, was unequivocally demonstrated only during ITP elevation with positive-pressure ventilation alone at slow rates. During vest CPR, LV outflow started promptly with the onset of compression, whereas LV inflow was delayed. At compression rates of 50 times/min and normal vascular filling pressures, the delay was sufficiently long that all LV filling occurred with release of compression. This is the pattern that would be expected with direct LV compression or "cardiac pump" physiology. During the early part of the compression phase, catheter tip transducer LV and left atrial pressure measurements demonstrated gradients necessitating mitral valve closure, while cineangiography showed dye droplets moving from the large pulmonary veins retrograde to the small pulmonary veins. When the compression rate was reduced and/or when intravascular pressures were raised with volume infusion, LV inflow was observed at some point during the compressive phase. Thus, under these conditions, features of both thoracic pump and cardiac pump physiology occurred within the same compression. Our findings are not explained by the conventional conceptions of either thoracic pump or cardiac compression CPR mechanisms alone.     

Gas compression in lungs decreases peak expiratory flow depending on resistance of peak flowmeter

Pedersen, O. F., T. F. Pedersen, and M. R. Miller. Gascompression in lungs decreases peak expiratory flow depending onresistance of peak flowmeter. J. Appl.Physiol. 83(5): 1517-1521, 1997.It has recentlybeen shown (O. F. Pedersen T. R. Rasmussen, Ø. Omland, T. Sigsgaard, P. H. Quanjer, and M. R. Miller. Eur. Respir. J. 9: 828-833, 1996) that the addedresistance of a mini-Wright peak flowmeter decreases peak expiratoryflow (PEF) by ~8% compared with PEF measured by a pneumotachograph.To explore the reason for this, 10 healthy men (mean age 43 yr, range33-58 yr) were examined in a body plethysmograph with facilitiesto measure mouth flow vs. expired volume as well as the change inthoracic gas volume (Vb) and alveolar pressure(PA). The subjects performed forced vital capacity maneuvers through orifices of different sizes andalso a mini-Wright peak flowmeter. PEF with the meter and other addedresistances were achieved when flow reached the perimeter of theflow-Vb curves. The mini-Wright PEF meter decreased PEF from 11.4 ± 1.5 to 10.3 ± 1.4 (SD) l/s(P < 0.001),PA increased from 6.7 ± 1.9 to 9.3 ± 2.7 kPa (P < 0.001), anincrease equal to the pressure drop across the meter, and caused Vb atPEF to decrease by 0.24 ± 0.09 liter(P < 0.001). We conclude that PEF obtained with an added resistance like a mini-Wright PEF meter is awave-speed-determined maximal flow, but the added resistance causes gascompression because of increasedPA at PEF. Therefore, Vb at PEFand, accordingly, PEF decrease.

     

Analysis of flow acceleration during erythrocyte filtration: Dependence of hematocrit and cell rigidity

At flow onset the blood filtration rate accelerates to a steady state, this may affect the interpretation of red blood cell (RBC) filterability. We studied the acceleration of flow while the pressure is built up across the filter to analyse effects of various hematocrits and RBC rigidity by glutaraldehyde (GA) hardening. This was analysed by a new filtration system with high time resolution and unlimited filtration volume. The system uses a digital balance that samples the accumulated weight (e.g., filtration rate through 5 μm Nuclepore membranes) with on-line computer communication. The filtration is computer controlled via a pneumatic valve. White blood cells (WBC) were removed prior to filtration by a WBC-eliminating filter to avoid clogging artifacts. When flow is initiated a steady state is reached at 0.3–0.4 s. This timing was also tested and confirmed by a video monitoring technique of filtration flow into a horizontal pipette. The digital balance has a mathematical function to reduce the effects of vibration noise; when this function was activated the apparent acceleration was retarded to 1.2 s. With any of these techniques the steady state timing did not vary with the hematocrit, however, the volume of filtered suspension during acceleration varied with both the hematocrit and the GA hardening (p < 0.001). Extrapolation to yield the initial filtration rate from the relative flow curve (RBC suspension divided by buffer flow) varied depending on if the acceleration phase was included or not. In the most unfavourable situation, with GA-hardened RBC, this difference was 340% (p < 0.01). The slope to calculate clogging rate was affected in a similar way. Moreover, with the most GA-hardened RBC a delay in flow onset was observed with this technique. The acceleration phenomenon may cause artifacts in systems employing volumederived filtration kinetics because of fixed volumes of filtrated medium.     

Mesh selection and filtration efficiency of the Continuous Plankton Recorder

The filtration efficiency [volume filtered/(inlet aperture areax distance travelled through the water)] and retention of copepodsby the Continuous Plankton Recorder (CPR) were measured in seatrials. Filtration efficiency was independent of tow speed (n= 14 trials, range of speeds 5–13 knots, F_1.12 = 0.1,P = 0.73), but was influenced by the extent to which the bodyof the CPR was sealed. The retention of copepods on the silkfiltering mesh routinely used in CPRs did not differ significantlyfrom that predicted for a 270 µm nylon mesh and did notvary with tow speed.     

Use of polyester leukocyte elimination filters in blood filterability research

We tested a new routine to eliminate leukocytes for blood rheology measurements using commercial leukocyte absorbing filters (here PALL RC400). These filters were punched out and fitted in smaller chambers through which blood was filtered under controlled suction pressure (< 30 mm Hg). This technique resulted in a very effective leukocyte elimination to 0.0022% but also a platelet reduction to 0.2%. The process causes a small but significant hemolysis with free hemoglobin, of the order of 0.06% of the filtered erythrocytes. A small fraction of the erythrocytes were retained in the filter, versus plasma, to reduce the hematocrit on the order of 1.4%. The leukocyte filtration did not cause any detectable functional trauma to the erythrocytes, measured as micro-pore filterability of normal and glutaraldehyde (GA) hardened erythrocytes. However, when 10% of the erythrocytes were hardened with GA, which caused an increase in pore clogging slope (p < 0.05), the additional passage through the leukocyte elimination filter removed this measured change in clogging. This observation suggests that the leukocyte elimination filter may selectively remove, not only leukocytes and platelets, but also hardened erythrocytes. Reticulocyte counting did not reveal any selective removal of young erythrocytes. In general, we find the presented method reproducible, efficient and easy for eliminating leukocytes for blood rheology research although the risk of removing undeformable erythrocytes must be considered.     

Wave-speed-determined flow limitation at peak flow in normal and asthmatic subjects

Pedersen, O. F., H. J. L. Brackel, J. M. Bogaard, and K. F. Kerrebijn. Wave-speed-determined flow limitation at peak flow innormal and asthmatic subjects. J. Appl.Physiol. 83(5): 1721-1732, 1997.The purpose ofthis study was to examine whether peak expiratory flow is determined bythe wave-speed flow-limiting mechanism. We examined 17 healthy subjectsand 11 subjects with stable asthma, the latter treated with inhaledbronchodilators and corticosteroids. We used an esophageal balloon anda Pitot-static probe positioned at five locations between the rightlower lobe and midtrachea to obtain dynamic area-transmural pressure(A-Ptm) curves as described (O. F. Pedersen, B. Thiessen, and S. Lyager. J. Appl.Physiol. 52: 357-369, 1982). From these curves weobtained cross-sectional area (A)and airway compliance (Caw = dA/dPtm) at PEF, calculated flow at wave speed {ws = A[A/(Caw*)^0.5],where  is density} and speed index is (SI = /ws). In 13 of 15 healthy andin 4 of 10 asthmatic subjects, who could produce satisfactory curves,SI at PEF was >0.9 at one or more measured positions. Alveolarpressure continued to increase after PEF was achieved, suggesting flowlimitation somewhere in the airway in all of these subjects. Weconclude that wave speed is reached in central airways at PEF in mostsubjects, but it cannot be excluded that wave speed is also reached inmore peripheral airways.

     

Influence of expiratory flow on closing capacity at low expiratory flow rates.

Single-breath oxygen (SBO2) tests at expiratory flow rates of 0.2, 0.5, and 1.01/s were performed by 10 normal subjects in a body plethysmograph. Closing capacity (CC)--the absolute lung volume at which phase IV began--increased significantly with increases in flow. Five subjects were restudied with a 200-ml bolus of 100% N2 inspired from residual volume after N2 washout by breathing 100% O2 and similar results were obtained. An additional five subjects performed SBO2 tests in the standing, supine, and prone positions; closing volume (CV)--the lung volume above residual volume at which phase IV began--also increased with increases of expiratory flow. The observed increase in CC with increasing flow did not appear to result from dependent lung regions reaching some critical "closing volume" at a higher overall lung volume. In normal subjects, the phase IV increase in NI concentration may be caused by the asynchronous onset of flow limitation occurring initially in dependent regions.     

Diurnal changes in the radius of a subalpine Norway spruce stem: their relation to the sap flow and their use to estimate transpiration

Diurnal changes in the stem radius of a subalpine mature Norway spruce were measured simultaneously with the flow of sap in xylem. Matric potentials in the soil were > -35 kPa. The kinetics of the flow were closely related to the changes in the radius of the stem resulting from depletion of its extensible tissues. The radius of the stem oscillated daily and, fairly independently of this, fluctuated over several days. The daily shrinkage (_d) was correlated with the daily flow through its base (Q_d). When the crown transpired little and was nearly saturated during rainy days, ASd tended to increase relative to Q_d. Using a linear relation, the estimates of flow by _d deviated less than ± 10% from the values measured by heat balance, provided that the periods of calibration in their ratio of dry to rainy days were comparable to those estimated. If the two periods differed in this respect, the estimates of flow deviated up to 42%. A quadratic relation yielded estimates that depended less on weather. It reduced maximal deviations to ±22%. Since _d additionally may represent the time pattern of the daily transpiration better than Q_d, analysing changes in the radius of stems may supplement or partly replace measurements of sap flow in stems.     

Exercise-induced blood flow in relation to muscle relaxation period

Background

Dynamic exercise is characterized by relaxation periods between contractions. The relaxation period should be considered as a causal factor for determining the magnitude of blood flow during dynamic exercise. The purpose of this study was to investigate the effect of muscle relaxation periods determined by the response of each subject on the exercise-induced blood flow response.

Methods

Seven healthy female subjects performed dynamic plantar flexions twice in succession; the duration of each flexion was 1- s and they were performed at an intensity of 15%, 30% and 50% of the maximal voluntary contraction (MVC). Based on the blood flow response after a single contraction, we set up intervals between two successive contractions; the intervals corresponded to 50% (pre-T_peak), 100% (T_peak), and 150% (post-T_peak) of the time required to reach peak blood flow.

Results

In all the conditions, upon cessation of the contraction, there was a progressive, beat-by-beat increase in the blood flow through the popliteal artery that peaked by the 5^th cardiac cycle. Peak values of blood flow achieved after exercise were significantly higher at pre-T_peak than at T_peak and post-T_peak (p < 0.05).

Conclusion

The result indicate that at three intervals based on the time taken to reach the peak value, the highest blood flow value was obtained at the pre-T_peak interval.

     

The sponge pump: the role of current induced flow in the design of the sponge body plan

Sponges are suspension feeders that use flagellated collar-cells (choanocytes) to actively filter a volume of water equivalent to many times their body volume each hour. Flow through sponges is thought to be enhanced by ambient current, which induces a pressure gradient across the sponge wall, but the underlying mechanism is still unknown. Studies of sponge filtration have estimated the energetic cost of pumping to be <1% of its total metabolism implying there is little adaptive value to reducing the cost of pumping by using "passive" flow induced by the ambient current. We quantified the pumping activity and respiration of the glass sponge Aphrocallistes vastus at a 150 m deep reef in situ and in a flow flume; we also modeled the glass sponge filtration system from measurements of the aquiferous system. Excurrent flow from the sponge osculum measured in situ and in the flume were positively correlated (r>0.75) with the ambient current velocity. During short bursts of high ambient current the sponges filtered two-thirds of the total volume of water they processed daily. Our model indicates that the head loss across the sponge collar filter is 10 times higher than previously estimated. The difference is due to the resistance created by a fine protein mesh that lines the collar, which demosponges also have, but was so far overlooked. Applying our model to the in situ measurements indicates that even modest pumping rates require an energetic expenditure of at least 28% of the total in situ respiration. We suggest that due to the high cost of pumping, current-induced flow is highly beneficial but may occur only in thin walled sponges living in high flow environments. Our results call for a new look at the mechanisms underlying current-induced flow and for reevaluation of the cost of biological pumping and its evolutionary role, especially in sponges.     

Blood flow, vascular resistance, and blood volume after hemorrhage in conscious adrenalectomized rat

Darlington, Daniel N., and Majid J. Tehrani. Bloodflow, vascular resistance, and blood volume after hemorrhage in conscious adrenalectomized rat. J. Appl.Physiol. 83(5): 1648-1653, 1997.Hemorrhage leadsto cardiovascular collapse and death in adrenal-insufficient animals.To determine whether the cardiovascular collapse is due to vasodilationand/or failure to restore blood volume, we used radiolabeledmicrospheres and ¹²⁵I-labeledalbumin to measure blood flow and blood volume in conscious adrenalectomized (ADX) rats after 15 ml · kg¹ · 3 min¹ hemorrhage. In ADXrats, hemorrhage led to a greater fall than in sham rats in blood flowin the stomach, small intestines, cecum, colon, spleen, hepatic portalvein, kidney, testis, lung, thymus, bone, fat, forebrain, cerebellum,and brainstem. The greater fall in blood flow was caused by an increasein vascular resistance in these organs except brain and hepatic artery.Sham rats maintained or increased brain and hepatic artery blood flowafter hemorrhage whereas flow decreased and remained depressed in ADXrats. ADX rats failed to restore blood volume, whereas sham ratscompletely restored blood flow by 2 h. We conclude that cardiovascularcollapse in ADX rats does not result from vasodilatation but may result from a failure to restore blood volume. The failure to restore bloodvolume and the low blood flow to organs, especially brain and liver,may contribute to mortality in ADX rats after hemorrhage.

     

Use of silicone membranes to enhance gas transfer during microbial fuel cell operation on carbon monoxide

Electricity generation in a microbial fuel cell (MFC) using carbon monoxide (CO) or synthesis gas (syngas) as a carbon source has been demonstrated recently. A major challenge associated with CO or syngas utilization is the mass transfer limitation of these sparingly soluble gases in the aqueous phase. This study evaluated the applicability of a dense polymer silicone membrane and thin wall silicone tubing for CO mass transfer in MFCs. Replacing the sparger used in our previous study with the membrane systems for CO delivery resulted in improved MFC performance and CO transformation efficiency. A power output and CO transformation efficiency of up to 18 mW (normalized to anode compartment volume) and 98%, respectively, was obtained. The use of membrane systems offers the advantage of improved mass transfer and reduced reactor volume, thus increasing the volumetric power output of MFCs operating on a gaseous substrate such as CO.     

Changes in bronchial and pulmonary arterial blood flow with progressive tension pneumothorax

Carvalho, Paula, Jacob Hildebrandt, and Nirmal B. Charan.Changes in bronchial and pulmonary arterial blood flow with progressive tension pneumothorax. J. Appl.Physiol. 81(4): 1664-1669, 1996.We studied theeffects of unilateral tension pneumothorax and its release on bronchialand pulmonary arterial blood flow and gas exchange in 10 adultanesthetized and mechanically ventilated sheep with chronicallyimplanted ultrasonic flow probes. Right pleural pressure (Ppl) wasincreased in two steps from 5 to 10 and 25 cmH₂O and then decreased to 10 and5 cmH₂O. Each level of Pplwas maintained for 5 min. Bronchial blood flow, right and leftpulmonary arterial flows, cardiac output(T),hemodynamic measurements, and arterial blood gases were obtained at theend of each period. Pneumothorax resulted in a 66% decrease inT, bronchialblood flow decreased by 84%, and right pulmonary arterial flowdecreased by 80% at Ppl of 25 cmH₂O(P < 0.001). At peak Ppl, themajority ofT was due toblood flow through the left pulmonary artery. With resolution ofpneumothorax, hemodynamic parameters normalized, although abnormalitiesin gas exchange persisted for 60-90 min after recovery and wereassociated with a decrease in total respiratory compliance.

     

Inter-Individual Difference in the Effect of Mirror Reflection-Induced Visual Feedback on Phantom Limb Awareness in Forearm Amputees

Objective

To test whether the phantom limb awareness could be altered by observing mirror reflection-induced visual feedback (MVF) in unilateral forearm amputees.

Methods

Ten unilateral forearm amputees were asked to perform bilateral (intact and phantom) synchronous wrist motions with and without MVF. During wrist motion, electromyographic activities in the extensor digitorum longus (EDL) and flexor carpi radialis muscles (FCR) were recorded with bipolar electrodes. Degree of wrist range of motion (ROM) was also recorded by electrogoniometry attached to the wrist joint of intact side. Subjects were asked to answer the degree of attainment of phantom limb motion using a visual analog scale (VAS: ranging from 0 (hard) to 10 (easy)).

Results

VAS and ROM were significantly increased by utilizing MVF, and the extent of an enhancement of the VAS and wrist ROM was positively correlated (r = 0.72, p<0.05). Although FCR EMG activity also showed significant enhancement by MVF, this was not correlated with the changes of VAS and ROM. Interestingly, while we found negative correlation between EDL EMG activity and wrist ROM, MVF generally affected to be increasing both EDL EMG and ROM.

Conclusions

Although there was larger extent of variability in the effect of MVF on phantom limb awareness, MVF has a potential to enhance phantom limb awareness, in case those who has a difficulty for the phantom limb motion. The present result suggests that the motor command to the missing limb can be re-activated by an appropriate therapeutic strategy such as mirror therapy.