Mathematical analysis of circulatory mixing process

The circulatory mixing process was analyzed as the time course of the dispersion of indicator after its injection into the heart. In simplified models, which had one or two lumped mixing chambers and circulatory pathways connected with them, it was suggested that the extent of dispersion could be evaluated by the variance of indicator distribution in the total circulating blood when the circulation time distributions between the chambers and the concentration curves in the chambers were known. The method of determining the circulation time distributions through the pulmonary, systemic and total circulations was derived and the actual distributions were obtained in dogs by indicator dilution techniques. With the use of these distributions, the time course of the circulatory mixing process was numerically calculated. The results showed that there was considerable difference in velocities of the process between the case of the right heart injection and the left heart injection of the indicator.     

Density indicator method to measure pulmonary blood flows

The injection of plasma, saline, or erythrocyte (RBC) concentrate into the pulmonary circulation produces a change in the gravimetric density of the blood outflow similar to the dilution curve of dye. We used an improved density-measuring system to assess the flow of these density indicators through the lung in vivo and in vitro perfused dog lobe. From the in vitro density-dilution curves of plasma and RBC concentrate we calculated the pulmonary flow rate and found it to be 1.04 +/- 0.02 (SD) times the measured one. The outflow-dilution curves of gravimetric density were not as broad as those of optical density following in vivo injection of plasma bolus containing indocyanine green, and the gravimetric measurements dipped to base line, whereas the optical measurement did not. The density-dilution curves of isotonic saline injection are similar to that of plasma. Following injection of RBC concentrates with the dye, density changes in the pulmonary outflow lag behind the emergence of the dye. This was presumably related to RBC aggregation in the concentrates. In reference to the injected plasma, no loss in the density indicators for saline and RBC injection was observed. Based on these results and the similarity of the density indicators to the blood, we conclude that the plasma and isotonic saline are good density indicators to be used for the determination of pulmonary blood flows.     

Bioreactor hydrodynamic effect on Escherichia coli physiology: experimental results and stochastic simulations

A microorganism circulating in a bioreactor can be submitted to hydrodynamic conditions inducing a significant effect on its physiology. The mixing time exhibited by the stirred bioreactor and the circulation of microorganisms are both involved in this reacting system. The mixing component determines the intensity of the concentration gradient and the circulation component determines the way in which the microorganism is exposed to this gradient. These two components linked to the experimental evaluation of microbial physiology can be analysed by a structured stochastic model in the case of a partitioned or “scale-down” reactor (SDR). A stochastic model indeed enables to simulate the mixing process as well as the circulation of microorganisms in SDRs. The superimposition of mixing and circulation processes determines the concentration profile experienced by a microorganism in the reactor. In the present case, the glucose concentration experienced by Escherichia coli has been modelled during a fed-batch culture. In this context, the use of a stochastic hydrodynamic model has permitted to point out an interesting feed pulse retardant effect in the SDRs. Nevertheless, the metabolic response of E. coli is not easy to interpret because of the possible simultaneous developments of overflow metabolism and mixed acid fermentation induced by the strong glucose concentration in the reactor.     

Routes of administration and uptake of tritiated nucleotides

Summary The uptake, incorporation and distribution of tritiated thymidine and uridine into visceral organs of immature female and male rats was studied. Radioautographs of various organs were prepared 5, 15 and 30 min after intraperitoneal administration. The distribution of the radioactivity was compared with sections obtained 30 min after intravenous injection of the same amount of nucleotides.The intraperitoneal injection was performed by directing the needle toward the right side of the abdominal cavity. Visceral organs from the injected side contained consistently more silver grains than those from the opposite side. Sections of the abdominal organs showed a decreasing concentration gradient of reduced silver grains extending from the serosal part of the organ to the deeper layers. In addition, initial labeling was observed in sectors of organs which protruded into the peritoneal cavity. In contrast, following intravenous administration of nucleotides a concentration gradient was not observed in any of the visceral organs.The results of the present study suggest that nucleotides administered intraperitoneally may penetrate the abdominal organs directly via the serosal surface without prior entry into the general circulation.     

Effect of phase transition on the kinetics of dye transport in phospholipid bilater structures.

Binding of 8-anilino-1-naphthalenesulfonate to dimyristoyl-L-alpha-lecithin bilayers enhances the fluorescence quantum yield of the dye molecule by 100-fold. By following the generation of fluorescence after a rapid mixing in a stopped-flow apparatus (mixing time 2 msec), kinetics of the binding of the fluorescence probe to the phospholipid vesicles has been investigated in the temperature range where the crystal-liquid crystal phase transition of the bilayer structures occurs. No reactions depending on the dye or the vesicle concentrations were detected. This suggests that the initial adsorption of the dye was very rapid. Two kinetic phases which appear in the 50 msec and the second time ranges are unimolecular. The faster one has a small amplitude and is observable in the entire temperature range studied. In the phase transition region the slower reaction becomes the major kinetic phase. It also increases the apparent concentration of bound dye by a factor of 2. These observations suggest that the 50-msec reaction has detected a reorientation of the probe molecule after the initial binding, and that the slow reaction represents a transport of the dye molecule into the inner layer of the lipid vesicle. The transport reaction is extremely temperature sensitive and exhibits a maximum rate at the midpoint of the bilayer phase transition (Tm = 24.1 degrees). the Arrhenius plot of the transport reaction shows a maximum at the Tm. the same temperature dependence was also observed for the bromothymol blue transport reaction. However, no such effects were detected for less amphiphilic molecules such as tetracycline, chlortetracycline, and pyrene. In the latter systems only a slight bending of the Arrhenius plots were seen at the phase transition temperature. Since the kinetics of the transport of 8-anilino-1-naphthalenesulfonate is sensitive to the physical state of the phospholipid bilayers this reaction may be used for probing membrane structures.     

Aeration is submerged fermentation

Observations on quantitative relationships between oxygen diffusion rate and product formation were made with penicillin, bacitracin, and gluconic acid. For penicillin and gluconic acid formation, no toxic oxygen concentration could be achieved in the broth, whereas concentration above approximately 7 mg. O₂/l. suppressed the bacitracin yield to an ever increasing extent. The intensity of mixing was measured by means of distributing a dye. With penicillin formation as an example, it was shown that the antibiotic yield is not only dependent on maintenance of a certain oxygen diffusion rate, but also on ensuring a necessary minimal mixing.     

Failure of injection of rat placental lactogen to inhibit prolactin in vivo

In an attempt to demonstrate a negative feedback of rat placental lactogen (rPL) on prolactin secretion, pregnant rats were hysterectomized and injected intraperitoneally with placental extracts. Hysterectomy alone prolonged the incidence of nocturnal prolactin surges and injection of placental extracts did not alter this response. However, the absence of rPL in the serum following the injections indicated a primary reason why no inhibition was seen. Only when rPL was given intravenously was there detectable amounts found in the blood. The slow disappearance of rPL from the circulation following hysterectomy in Day 11 pregnant rats suggests that the lack of rPL in the blood following ip injection of placental extracts is not due to rapid clearance of rPL from blood. The failure to show a negative feedback of rPL on prolactin in vivo may be due primarily to the lack of appearance of rPL in the circulation following an ip injection of placental extracts.     

Characterisation of the Egeria densa Planch. leaf symplast

The hydrophyllic dyes fluorescein glutamic acid, fluorescein glutamylglutamic acid (F(Glu)₂), fluorescein hexaglycine, fluorescein leucyldiglutamyl-leucine and 6-carboxyfluorescein are unable to pass the plasmalemma in leaves of E. densa. However, when injected into single cells the dye conjugates of molecular weight 665 dalton or less move freely from cell-to-cell. This intercellular movement presumably occurs via the plant symplast. Movement of F(Glu)₂ from the injected cell occurs with greatly reduced frequency when Ca²⁺, Mg²⁺ or Sr²⁺ are injected into the cell immediately prior to the dye. The fraction of dye injections leading to movement declines with increasing group II ion concentration in the electrode tip, up to 10 mM. Sodium and K ions do not affect dye movement. When dye injection is delayed 30 min after Ca²⁺ injection, dye movement is no longer inhibited. Thus the cells recover from the Ca²⁺ injection, indicating that the ion does not cause major cell damage. Recovery from Mg²⁺ injection is not complete within 60 min. Treatment of leaves with chemicals expected to raise the concentration of free intracellular group II ions, notably the mitochondrial uncoupler carbonyl cyanide p-trifluoromethoxyphenyl hydrazone, the inhibitor of mitochondrial Ca²⁺ uptake trifluralin, or the ionophore A23187 also inhibits dye movement, while the calmodulin inhibitor trifluoperazine does not. Cytoplasmic streaming is inhibited by Ca²⁺ or Mg²⁺ injection and by the metabolic inhibitors. However when streaming is stopped by cytochalasin B, dye movement is not inhibited. Hence steaming is not necessary for dye movement. Thus the cytoplasmic concentration of free group II ions may directly regulate the permeability of the plant symplast.     

A radiological study of the central circulation in the lungfish, Protopterus aethiopicus

The dipnoan heart is only in part structurally developed to support a separated circulation in pulmonary and systemic circuits. In the present investigation biplane angiocardiography has been used to describe the extent of such a double circulation and the factors which may modify it in the African lungfish, Protopterus aethiopicus. Contrast injections in the pulmonary vein revealed a clear tendency for aerated blood returing from the lungs to be selectively dispatched to the anterior branchial arteries giving rise to the major systemic circulation. Contrast injections in the vena cava delineated the sinus venosus as a large receiving chamber for systemic venous blood. Contraction of the sinus venosus discharged blood into the right, posterior part of the partially divided atrial space. Contrast injection in the pulmonary vein showed that vessel to pass obliquely from right to left such that blood was emptied distinctly into the left side of the atrium. During contraction the atrial space tended to retain a residual volume in its anterior undivided part which minized mixing. Ventricular filling occurred through separate right and left atrio-ventricular connections. Right-left separation in most of the ventricle was maintained by the partial ventricular septum, the trabeculated, spongelike myocardium and the mode of inflow from the atria. Mixing in the anterior undivided portion of the ventricle during the ejection phase was slight due to a streamlined ejection pattern. The outflow through the bulbus cordis occurred in discrete streams which in part were structurally separated by well developed spiral folds. In the anterior bulbus segment the spiral folds are fused and make completely separate dorsal and ventral outflow tracts. The ventral bulbus channel provides blood to the three anterior branchial arteries. The second and third branchial arteries are large and represent direct shunts to the dorsal aorta. The fourth and fifth branchial arteries are gill bearing and receive blood form the dorsal bulbus channel. The most posterior epibranchial vessels give rise to the pulmonary arteries.     

Induced optical activity of chondroitin sulfate c–acridine orange complexes

Chondroitin sulfate C (CSC) and acrdiine orange (AO) formed two types of complexes at neutral pH, depending upon the order of mixing. The induced optical activity of AO was much more pronounced when the polysaccharide was added to dye than the dye to polymer (final concentration of dye was 5 × 10⁵M). The difference in aggregation of the dye molecules is believed to be responsible for the observed peculiarities. The Cotton effects of the CSC-to-dye solution displayed a sharp inversion near 59°C. and the profile at 76°C. was almost a mirror image of that at room temperature. At pH 1.3, however, the order of mixing became unimportant, suggesting that the carboxylate on the polysaccharide way involved more intimately than were sulfates in the peculiarities of the Cotton effects.     

Interaction between DMPC liposomes and HM-PNIPAM polymer

The interactions of hydrophobically-modified poly-(N-isopropylacrylamides) (HM-PNIPAM) and dimyristoylphosphatidylcholine (DMPC) vesicles were investigated by the effect of the polymer on the binding of a fluorescent dye, oxonol VI, to DMPC vesicles, and on its diffusion across the membrane. On mixing with the vesicles, the dye exhibits an increase in fluorescence, which occurs in a two-stage process. The process was monitored by stopped-flow fluorescence spectrophotometry. According to the dependence of the reciprocal relaxation time on vesicle concentration, the rapid stage seems to be due to the second-order binding of the dye to the lipid membrane, a process that is almost diffusion-controlled, whereas the slow process is attributed to movement of the dye within the membrane phase. The polymer did not significantly affect the rate constant of the binding step, but it slowed down slightly the dissociation process of the dye from the membrane. However, the polymer affected the second stage, causing an increase in the reciprocal of its relaxation time, which suggests that the polymer makes the vesicle membrane more fluid.     

The oral-aboral axis of a sea urchin embryo is specified by first cleavage

Several lines of evidence suggest that the oral-aboral axis in Strongylocentrotus purpuratus embryos is specified at or before the 8-cell stage. Were the oral-aboral axis specified independently of the first cleavage plane, then a random association of this plane with the blastomeres of the four embryo quadrants in the oral-aboral plane (viz. oral, aboral, right and left) would be expected. Lineage tracer dye injection into one blastomere at the 2-cell stage and observation of the resultant labeling patterns demonstrates instead a strongly nonrandom association. In at least ninety percent of cases, the progeny of the aboral blastomeres are associated with those of the left lateral blastomeres and the progeny of the oral blastomeres with the right lateral ones, respectively. Thus, ninety percent of the time the oral pole of the future oral-aboral axis lies 45 degrees clockwise from the first cleavage plane as viewed from the animal pole. The nonrandom association of blastomeres after labeling of the 2-cell stage implies that there is a mechanistic relation between axis specification and the positioning of the first cleavage plane.     

Interaction between acridine orange and polyriboadenylic acid

The absorption spectra and circular dichroism of aqueous solutions of acridine orange mixed with polY(riboadenylic acid) [poly(rA)] have been measured for different mixing ratios at acid and neutral pH. The binding ratio of dye to poly(rA) has been determined by equilibrium dialysis. At acid pH where poly(rA) is in a double-stranded helix, monomeric dye molecules are intercalated between base pairs, first sparsely and then at neighbouring sites with mutual coupling, as the nucleotide-to-dye mixing ratio decreases. In the presence of excess dye, dimeric dye molecules of antiparallel type are bound to phosphate groups electrostatically and stack together to form linear sequences along a poly(rA) chain. At neutral pH where poly(rA) is single-stranded, isolated intercalation of monomeric dye molecules can occur in the helical parts. At intermediate mixing ratios, half-intercalated dimeric dye molecules are bound to adjacent sites and electronically coupled, inducing characteristic circular dichroism. In the presence of higher amounts of dye, external stacking of dimeric dye molecules of antiparallel type occurs along a poly(rA) chain. The binding of dye cations is suppressed to some degree at acid pH compared to that at neutral pH, owing to the repulsion exerted by protonated adenine bases.     

Perfluoro compounds as artificial erythrocytes.

Some liquid perfluoro compounds dissolve relatively large amounts of oxygen and can be used in dispersed form as substitutes for erythrocytes. The commonly used perfluoro compounds contain about the same amount of oxygen as do equal volumes of erythrocytes when equilibrated with 100% oxygen. However, when equilibrated with alveolar air, the perfluoro compounds contain much less oxygen than erythrocytes. The dispersed fluorochemicals are adequate substitutes for perfusion of isolated preparations of mammalian brain, heart kidney, lung and liver. However, when put into the circulation of the intact animal, the dispersed fluorochemicals tends to produce lesions of the lungs, dilation of the right heart, and ultimately fatal hypoxia. It is suggested that the course of events following intravenous injection of dispersed fluorochemical is initiated by an interaction of the perfluoro particles with blood platelets or blood clotting factors. The ensuing intravascular clotting could then cause the changes in the lungs which lead to a marked increase in pulmonary artery pressure and dilation of the right heart. These events would terminate in fatal hypoxia due to pulmonary pathology and heart failure.     

Starch-primulin fluorescence

Summary Intact starch grains with primulin give initially a blue fluorescence that is weakly polarized. As more dye enters the grain, the fluorescence color gradually changes to a yellow-green fluorescence that is strongly polarized. Where the structure of the grain is disorganized, the primulin-starch complex fluoresces yellow. A bright yellow rim about all intact grains is interpreted as a Becke line.Fluorescence colors of primulin-starch are essentially unaffected by hydrogen ion concentration, by the presence of salts, by the solvent in which the primulin is dissolved, and by the dye fraction (of acetoneseparated primulin fractions) used as a solute. These colors have no relation to the type of starch in the primulin-starch complex.Absorption and fluorescence spectra of primulin and its fractions vary with the concentration of the dye, the nature of the solvent, and the nature of the fraction. Three types of primulin-solvent association are envisioned: primulin anion in water; primulin molecule hydrogen-bonded to solvent or substrate molecule in non-aqueous medium; primulin dimeric association-at high concenntrations-in non-aqueous medium.Primulin-starch fluorescence colors are explicable on the basis of dye concentration and pore size in the starch grain. Pore spaces that will accept dye molecules are estimated to have a diameter between 7 and 20°.     

Distinct Patterns of Cerebral Extravasation by Evans Blue and Sodium Fluorescein in Rats

The Evans blue dye (EBD; 961 Da) and the sodium fluorescein dye (NaF; 376 Da) are commonly used inert tracers in blood-brain barrier (BBB) research. They are both highly charged low molecular weight (LMW) tracers with similar lipophobic profiles. Nevertheless, the EBD binds to serum albumin (69,000 Da) to become a high molecular weight (HMW) protein tracer when injected into the circulation, whereas the NaF remains an unbound small molecule in the circulation. In this study, rats were injected with equal doses of either EBD or NaF to monitor their blood and tissue distribution. The EBD was largely confined to the circulation with little accumulation in the peripheral organ and even less accumulation in the central tissue, whereas the NaF distributed more evenly between the blood and the peripheral organ but was also largely excluded from the central tissue. Importantly, the EBD crossed the BBB most effectively at the prefrontal cortex and the cerebellum, and most poorly at the striatum. In marked contrast, the NaF was evenly distributed throughout the brain. Finally, the EBD exhibited this same peculiar tissue distribution profile when administered by either bolus injection or slow infusion. Our study suggests that different regions of the brain are equally permeable to LMW inert dyes like the NaF, but are markedly different in permeability to HMW proteins such as EBD-labelled serum albumin.     

Dynamic components of interrelation among the parameters of heart preload, venous return and central venous pressure

In acute experiments on cats, in applying of original methodical approach--control of systemic circulation by the aid of computerized negative feedback loop changing the volume of circulating blood (method of biological feedback)--first were experimentally measured and analyzed the dynamic characteristics of relationship between central venous pressure and venous return of blood to the right heart. The following positions are offered and validated in the work. (1) It is shown that the passive component (mechanical compliance) is more important than active one (active myogenic component) in the small circle of circulation being compared to large one. (2) Venous return plays the leading role in forming the shifts of central venous pressure directly during developing of the transition processes of systemic circulation caused by the norepinephrine injection and the linear type of this link is proved directly during the development of the cardiovascular shift. (3) The dynamic characteristics of relationship between venous return and central venous pressure during the geodynamical reaction caused by the shifts of intravascular blood volume are experimentally measured and mathematically analyzed. It is revealed that dynamic summands of this link may overbalance the static ones known before in influence on the total shifts in developing of the systemic reaction of circulation and this influence increases when the velocity of changes in studied parameters of circulation becomes more.     

Stimulation by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine of rat hepatic polyamine biosynthesis in vivo

Intraperitoneal injection of the phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (IBMX), resulted in a rapid and transient induction of rat hepatic ornithine decarboxylase (ODC) activity. Maximal activity was found about 5 hr after application. The levels of putrescine and spermidine increased accordingly, reaching a maximum at 7 and 12 hr following injection, respectively, while the concentration of spermine remained almost constant. The implications of these findings are discussed in relation to the mechanism of induction of ornithine decarboxylase and concomitant polyamine biosynthesis.     

Magnetic resonance of a dextran-coated magnetic fluid intravenously administered in mice

Magnetic resonance was used to investigate the kinetic disposition of magnetite nanoparticles (9.4 nm core diameter) from the blood circulation after intravenous injection of magnetite-based dextran-coated magnetic fluid in female Swiss mice. In the first 60 min the time-decay of the nanoparticle concentration in the blood circulation follows the one-exponential (one-compartment) model with a half-life of (6.9 +/- 0.7) min. The X-band spectra show a broad single line at g approximately 2, typical of nanomagnetic particles suspended in a nonmagnetic matrix. The resonance field shifts toward higher values as the particle concentration reduces, following two distinct regimes. At the higher concentration regime (above 10(14) cm(-3)) the particle-particle interaction responds for the nonlinear behavior, while at the lower concentration regime (below 10(14) cm(-3)) the particle-particle interaction is ruled out and the system recovers the linearity due to the demagnetizing field effect alone.     

Mixing rate of phosphate between plasma and interstitial body fluid of cows

Radiophosphate was injected into the left jugular vein of dairy cows. Blood samples were taken frequently from the right jugular vein during the first hour after injection. Between 20 minutes and 1 hour after injection, the decrease in plasma radioactivity could be formulated as a first order process, designated as "process 3," with a turnover time of 50 minutes. From 5 to 20 minutes after injection the decrease in plasma activity could be interpreted as the result of mixing plasma phosphate with another phosphate pool, designated as the second pool. The capacity of this second pool was derived as a constant in a kinetic equation, so chosen that the resulting mixing rates were independent of time. For two cows the capacity of the second pool was 5 and 8 times, respectively. the phosphate content of the plasma. This result led to the working hypothesis that the major part of the second pool was the phosphate in the interstitial tissue fluid. The turnover time of the plasma phosphate in the mixing process with the second pool amounted to an average of 14 minutes for 5 lactating cows, and an average of 21 minutes for 2 dry cows. This result was obtained under the assumption that the slow first order process 3 is parallel to the mixing process. The assumption that the slower first order process is in series with the mixing process reduces the resulting mixing time to about four-fifths of that reported above. The calculation of process 2 which deviates from first order may be applicable to numerous turnover processes in which both exchange pools have a limited capacity.