Evaluation of Surface Free Energy of Various Fruit Epicarps Using Acid�CBase and Zisman Approaches

Surface free energy (SFE; γ _SV) of 16 fruit epicarps present on the Chilean market was calculated by two approaches: the acid–base and Zisman. The results show that the fruit epicarps were low surface energy since the magnitude of γ _SV falls within a narrow range, between 37 and 44 mJ m^− 2. Zisman approach gave a critical surface tension values, γ _cr lower than the SFE calculated by the acid–base approach. Significant differences in SFE between the fruits may be explained by the variation in the chemical composition of epicuticular waxes. The polar (g^AB_SV\gamma^{\rm AB}_{\rm SV}) and apolar (g^LW_SV\gamma^{\rm LW}_{\rm SV}) components of the SFE were also calculated and a mathematical relation was between both values was found. Values of g^AB_SV\gamma^{\rm AB}_{\rm SV} and g^LW_SV\gamma^{\rm LW}_{\rm SV} could also be associated with the fruit family and the tissue origins in the ovary region. Finally, it has been shown that fruit epicarps exhibited predominantly electron-donator behaviour since $\gamma_{\rm SV}^- > \gamma_{\rm SV}^+$\gamma_{\rm SV}^- > \gamma_{\rm SV}^+. We believe that the results reported here can potentially impact in food engineering because the compatibility of coatings and fruit epicarps depends on the interaction of their respective chemical and physical properties.     

Environment and feeding change the ability of heart rate to predict metabolism in resting Steller sea lions (<Emphasis Type="Italic">Eumetopias jubatus</Emphasis>)

The ability to use heart rate (fh) to predict oxygen consumption rates ( [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} ) in Steller sea lions and other pinnipeds has been investigated in fasting animals. However, it is unknown whether established fh: [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} relationships hold under more complex physiological situations, such as when animals are feeding or digesting. We assessed whether fh could accurately predict [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} in trained Steller sea lions while fasting and after being fed. Using linear mixed-effects models, we derived unique equations to describe the fh: [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} relationship for fasted sea lions resting on land and in water. Feeding did not significantly change the fh: [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} relationship on land. However, Steller sea lions in water displayed a different fh: [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} relationship after consuming a 4-kg meal compared with the fasting condition. Incorporating comparable published fh: [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} data from Steller sea lions showed a distinct effect of feeding after a 6-kg meal. Ultimately, our study illustrated that both feeding and physical environment are statistically relevant when deriving [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} from telemetered fh, but that only environment affects the practical ability to predict metabolism from fh. Updating current bioenergetic models with data gathered using these predictive fh: [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} equations will yield more accurate estimates of metabolic rates of free-ranging Steller sea lions under a variety of physiological, behavioral, and environmental states.     

Finite element–based injury metrics for pulmonary contusion via concurrent model optimization

This study explores the relationship between impact severity and resulting pulmonary contusion (PC) for four impact conditions using a rat model of the injury. The force–deflection response from a Finite Element (FE) model of the lung was simultaneously matched to experimental data from distinct impacts via a genetic algorithm optimization. Sprague-Dawley rats underwent right-side thoracotomy prior to impact. Insults were applied directly to the lung via an instrumented piston. Five cohorts were tested: a sham group and four groups experiencing lung insults of varying degrees of severity. The values for impact velocity (V) and penetration depth (D) of the cohorts were Group 1, (V = 6.0 m · s⁻¹, D = 5.0 mm), Group 2, (V = 1.5 m · s⁻¹,D = 5.0 mm), Group 3, (V = 6 m · s⁻¹, D = 2.0 mm), and Group 4, (V = 1.5 m · s⁻¹, D = 2.0 mm). CT scans were acquired at 24 h, 48 h, and 1 week post-insult. Contusion volume was determined through segmentation. FE-based injury metrics for PC were determined at 24 h and 1 week post-impact, based on the observed volume of contusion and first principal strain. At 24 h post-impact, the volume of high radiopacity lung (HRL) was greatest for the severe impact group (mean HRL = 9.21 ± 4.89) and was significantly greater than all other cohorts but Group 3. The concurrent optimization matched simulated and observed impact energy within one standard deviation for Group 1 (energy = 3.88 ± 0.883 mJ, observed vs. 4.47 mJ, simulated) and Group 2 (energy = 1.46 ± 0.403 mJ, observed vs. 1.50 mJ, simulated) impacts. Statistically significant relationships between HRL and impact energy are presented. The FEA-based injury metrics at 24 h post-contusion are e_max·[(e)\dot]_max{\varepsilon_{\max}\cdot \dot {\varepsilon}_{\max}} exceeding 94.5 s⁻¹, ε _max exceeding 0.284 and [(e)\dot]_max{\dot{\varepsilon}_{\max}} exceeding 470 s⁻¹. Thresholds for injury to the lung still present at 1 week post-impact were also determined. They are e_max·[(e)\dot]_max{\varepsilon_{\max}\cdot \dot {\varepsilon}_{\max}} exceeding 149 s⁻¹, ε _max exceeding 0.343 and [(e)\dot]_max{\dot{\varepsilon}_{\max}} exceeding 573 s⁻¹. A mesh sensitivity study found that thresholds based on strain rate were more sensitive to changes to mesh density than the threshold based on strain only.     

AMP-activated protein kinase plays a role in initiating metabolic rate suppression in goldfish hepatocytes

In the present study, we test the hypothesis that AMP-activated protein kinase (AMPK) initiates metabolic rate suppression in isolated goldfish hepatocytes. To accomplish this, we attempted to pharmacologically activate AMPK in goldfish hepatocytes with 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) and the thienopyridone, A769662, to examine the effects of AMPK activation on eukaryotic elongation factor-2 (eEF2), protein synthesis, and cellular oxygen consumption rate ( [(M)\dot]_{\textO 2} \dot{M}_{{{\text{O}}_{ 2} }} ). Goldfish hepatocytes treated with 1 mM AICAR under normoxic conditions (>200 μM O₂) showed a modest but significant 1.1-fold increase in AMPK phosphorylation, a 7.5-fold increase in AMPK activity, a 1.4-fold increase in eEF2 phosphorylation, and a 24% decrease in [(M)\dot]_{\textO 2} \dot{M}_{{{\text{O}}_{ 2} }} . At physiologically relevant [O₂] (<40 μM O₂), the addition of 1 mM AICAR resulted in only a 13% decrease in cellular [(M)\dot]_{\textO 2} \dot{M}_{{{\text{O}}_{ 2} }} with no change in sensitivity to [O₂] as assessed by estimates of cellular P₅₀ and P₉₀ values. The addition of compound C, a general protein kinase inhibitor, after AICAR incubation did not reverse the effects of AICAR on [(M)\dot]_{\textO 2} \dot{M}_{{{\text{O}}_{ 2} }} in normoxia. Treatment of hepatocytes with ≤200 μM A769662 did not affect AMPK activity, AMPK phosphorylation, eEF2 phosphorylation, or cellular [(M)\dot]_{\textO 2} \dot{M}_{{{\text{O}}_{ 2} }} . These data suggest that A769662 is not an activator of AMPK in goldfish hepatocytes. Although our study provides support for the hypothesis that AMPK plays a role in initiating metabolic rate suppression in goldfish hepatocytes, this support must be viewed cautiously because of the known off-target effects of the pharmacological agents used.     

Cardiorespiratory responses to hypoxia in the African catfish, <Emphasis Type="Italic">Clarias gariepinus</Emphasis> (Burchell 1822), an air-breathing fish

The African catfish, Clarias gariepinus, possesses a pair of suprabranchial chambers located in the dorsal-posterior part of the branchial cavity having extensions from the upper parts of the second and fourth gill arches, forming the arborescent organs. This structure is an air-breathing organ (ABO) and allows aerial breathing (AB). We evaluated its cardiorespiratory responses to aquatic hypoxia. To determine the mode of air-breathing (obligate or accessory), fish had the respiratory frequency (f _R) monitored and were subjected to normoxic water (PwO₂ = 140 mmHg) without becoming hyperactive for 30 h. During this period, all fish survived without displaying evidences of hyperactivity and maintained unchanged f _R, confirming that this species is a facultative air-breather. Its aquatic O₂ uptake ( [(V)\dot]\textO₂ \dot{V}{\text{O}}_{2} ) was maintained constant down to a critical PO₂ (PcO₂) of 60 mmHg, below which [(V)\dot]\textO₂ \dot{V}{\text{O}}_{2} declined linearly with further reductions of inspired O₂ tension (PiO₂). Just above the PcO₂ the ventilatory tidal volume (V _T) increased significantly along with gill ventilation ( [(V)\dot]_\textG \dot{V}_{\text{G}} ), while f _R changed little. Consequently, the water convection requirement ( [(V)\dot]_\textG /[(V)\dot]\textO₂ ) \left( {\dot{V}_{\text{G}} /\dot{V}{\text{O}}_{2} } \right) increased steeply. This threshold applied to a cardiac response that included reflex bradycardia. AB was initiated at PiO₂ = 140 mmHg (normoxia) and air-breathing episodes increased linearly with more severe hypoxia, being significantly higher at PiO₂ tensions below the PcO₂. Air-breathing episodes were accompanied by bradycardia pre air-breath, to tachycardia post air-breath.     

A simple method for measuring signs of <Superscript>1</Superscript>H<Superscript>N</Superscript> chemical shift differences between ground and excited protein states

NMR relaxation dispersion spectroscopy is a powerful method for studying protein conformational dynamics whereby visible, ground and invisible, excited conformers interconvert on the millisecond time-scale. In addition to providing kinetics and thermodynamics parameters of the exchange process, the CPMG dispersion experiment also allows extraction of the absolute values of the chemical shift differences between interconverting states, | \Updelta [(w)\tilde] | \left| {\Updelta \tilde{\omega }} \right| , opening the way for structure determination of excited state conformers. Central to the goal of structural analysis is the availability of the chemical shifts of the excited state that can only be obtained once the signs of \Updelta [(w)\tilde] \Updelta \tilde{\omega } are known. Herein we describe a very simple method for determining the signs of ¹H^N \Updelta [(w)\tilde] \Updelta \tilde{\omega } values based on a comparison of peak positions in the directly detected dimensions of a pair of ¹H^N–¹⁵N correlation maps recorded at different static magnetic fields. The utility of the approach is demonstrated for three proteins that undergo millisecond time-scale conformational rearrangements. Although the method provides fewer signs than previously published techniques it does have a number of strengths: (1) Data sets needed for analysis are typically available from other experiments, such as those required for measuring signs of ¹⁵N \Updelta [(w)\tilde] \Updelta \tilde{\omega } values, thus requiring no additional experimental time, (2) acquisition times in the critical detection dimension can be as long as necessary and (3) the signs obtained can be used to cross-validate those from other approaches.     

Comparative analysis of oxygen transfer rate distribution in stirred bioreactor for simulated and real fermentation broths

Study of the distribution of the oxygen mass transfer coefficient, k _l a, for a stirred bioreactor and simulated (pseudoplastic solutions of carboxymethylcellulose sodium salt) bacterial (P. shermanii), yeast (S. cerevisiae), and fungal (P. chrysogenum free mycelia) broths indicated significant variation of transfer rate with bioreactor height. The magnitude of the influence of the considered factors differed from one region to another. As a consequence of cell adsorption to bubble surface, the results indicated the impossibility of achieving a uniform oxygen transfer rate throughout the whole bulk of the microbial broth, even when respecting the conditions for uniform mixing. Owing to the different affinity of biomass for bubble surface, the positive influence of power input on k _l a is more important for fungal broths, while increasing aeration is favorable only for simulated, bacterial and yeast broths. The influence of the considered factors on k _l a were included in mathematical correlations established based on experimental data. For all considered positions, the proposed equations for real broths have the general expression k_l a = aC_X^b ( \fracP_a V )^g v_S^d , k_{\rm l} a = \alpha C_{\rm X}^{\beta } \left( {{\frac{{P_{\rm a} }}{V}}} \right)^{\gamma } v_{\rm S}^{\delta } , exhibiting good agreement with experimental results (with maximum deviations of ±10.7% for simulated broths, ±8.4% for P. shermanii, ±9.3% for S. cerevisiae, and ±6.6% for P. chrysogenum).     

Influence of {\text{NH - }}{{\text{S}}^\gamma } bonding interactions on the structure and dynamics of metallothioneins

Mammalian metallothioneins ( \textM₇^\textIIMTs {\text{M}}_7^{\text{IIMTs}} ) show a clustered arrangement of the metal ions and a nonregular protein structure. The solution structures of Cd₃-thiolate cluster containing β-domain of mouse β-MT-1 and rat β-MT-2 show high structural similarities, but widely differing structure dynamics. Molecular dynamics simulations revealed a substantially increased number of \textNH - \textS^g {\text{NH - }}{{\text{S}}^\gamma } hydrogen bonds in β-MT-2, features likely responsible for the increased stability of the Cd₃-thiolate cluster and the enfolding protein domain. Alterations in the \textNH - \textS^g {\text{NH - }}{{\text{S}}^\gamma } hydrogen-bonding network may provide a rationale for the differences in dynamic properties encountered in the β-domains of MT-1, -2, and -3 isoforms, believed to be essential for their different biological function.     

Self-thinning lines of organs and aboveground parts based on allometric relationships in overcrowded Pinus densiflora stands

The allometric relationships of mean tree height [`(H)]( μ [`(w)]_x^q ) \bar{H}( \propto \bar{w}_{\rm {x}}^{\theta } ) and of organ mass density [`(d)]<sub>x</sub> ( μ [`(w)]_x^d ) \bar{d}_{\rm {x}} ( \propto \bar{w}_{\rm {x}}^{\delta } ) to mean organ mass [`(w)]_x \bar{w}_{\rm {x}} were studied in self-thinning Pinus densiflora Sieb. et Zucc. stands. Tree height increased significantly with increasing mean mass of organs and aboveground parts on log–log coordinates. The value of the allometric constant θ ranged from 0.2878 to 0.3349. On the other hand, the constant value δ was not significantly different from zero, except for leaves. The value of the allometric constant δ ranged from −0.2926 to 0.0120. According to Weller’s allometric model, the slope of the self-thinning line was calculated from the allometric constants θ and δ. The thinning slope was estimated to be −1.51 in stem, −1.39 in branches, −1.00 in leaf and −1.41 in aboveground parts, respectively. Mass density was high in stem, medium in branches and low in leaves. Mean leaf mass density decreased significantly with decreasing stand density on log–log coordinates, which could be interpreted as indicating the importance of the constant final leaf biomass in overcrowded P. densiflora stands. The self-thinning exponents of branch, stem and aboveground parts were not significantly different from 3/2, which indicated that the 3/2 power law of self-thinning holds for stem mass, branch mass and aboveground mass in overcrowded P. densiflora stands.     

Nocturnal lizards from a cool-temperate environment have high metabolic rates at low temperatures

Ectotherms from low-temperature environments have higher metabolic rates at low temperatures than those from warm-temperature environments. We predicted that nocturnal lizards, which are active at much lower environmental temperatures than diurnal lizards, would also have higher metabolic rates at low temperatures, and by association a lower thermal sensitivity (Q ₁₀) than diurnal and crepuscular lizards. We measured the rate of oxygen consumption ( [(V)\dot]\textO ₂ \dot{V}{\text{O}}_{ 2} ) of eight cool-temperate species of lizard (four nocturnal, three diurnal, and one crepuscular) at 13 and 26°C and analyzed log transformations of these data using log mass as a covariate. As expected, [(V)\dot]\textO ₂ \dot{V}{\text{O}}_{ 2} was positively correlated with temperature in all eight species, with [(V)\dot]\textO ₂ \dot{V}{\text{O}}_{ 2} being two to four times higher at 26°C than at 13°C. As predicted, at 13°C (but not 26°C) the [(V)\dot]\textO ₂ \dot{V}{\text{O}}_{ 2} was significantly higher in nocturnal than diurnal lizards. Species-specific differences and mass scaling factors explain the patterns of thermal sensitivity seen among these eight lizard species. Thermal sensitivity is strongly influenced by mass, with smaller species generally having higher thermal sensitivity of their metabolic rate, and this result deserves further exploration among other ectotherms. We conclude that, along with the previously reported lower cost of locomotion found in nocturnal lizards, they also partially offset the thermal handicap of activity at low body temperatures by having an elevated [(V)\dot]\textO ₂ \dot{V}{\text{O}}_{ 2} at lower temperatures.     

Determination of the average shear rate in a stirred and aerated tank bioreactor

A method for evaluating the average shear rate () in a stirred and aerated tank bioreactor has been proposed for non-Newtonian fluids. The volumetric oxygen transfer coefficient (k _L a) was chosen as the appropriate characteristic parameter to evaluate the average shear rate (). The correlations for the average shear rate as a function of N and rheological properties of the fluid (K and n) were obtained for two airflow rate conditions (ϕ_air). The shear rate values estimated by the proposed methodology lay within the range of the values calculated by classical correlations. The proposed correlations were utilized to predict the during the Streptomyces clavuligerus cultivations carried out at 0.5 vvm and four different rotational impeller speeds. The results show that the values of the average shear rate () varied from 437 to 2,693 s⁻¹ by increasing with N and flow index (n) and decreasing with the fluid consistency index (K).     

Topography of nucleic acid helices in solutions. 3. Interactions of spermine and spermidine derivatives with polyadenylic-polyuridylic and polyinosinic-polycytidylic acid helices

The synthesis of spermine derivatives (II), \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R}_1 {\rm R}_{\rm 2} {\rm R}_{\rm 3} \mathop {\rm N}\limits^ + \left( {{\rm CH}_2 } \right)_3 \mathop {\rm N}\limits^ + {\rm R}_{\rm 1} {\rm R}_{\rm 2} \left( {{\rm CH}_2 } \right)_2 ]_2 \cdot 4{\rm X}^ - $\end{document}, and spermidine derivatives (III), \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R}_1 {\rm R}_{\rm 2} {\rm R}_{\rm 3} \mathop {\rm N}\limits^ + \left( {{\rm CH}_2 } \right)_4 \mathop {\rm N}\limits^ + {\rm R}_{\rm 1} {\rm R}_{\rm 2} \left( {{\rm CH}_2 } \right)_3 \mathop {\rm N}\limits^ + {\rm R}_{\rm 1} {\rm R}_{\rm 2} {\rm R}_3 \cdot 3{\rm X}^ - $\end{document}, are reported. The effects of these salts on the helix–coil transition of rA–rU and rI–rC helices were examined. Increasing the size of the hydrophobic substituents, R¹, R², and R³ lowers the degree of stabilization of the helical structure. The disproportionation reaction, 2rA–rU→rA–rU₂ + rA occurs readily with salts II and III, especially when the substituents, R₁, R₂, and R₃ are small, i.e., H or Me. Spermine is found to stabilize the rA–rU² and rI–rC helices to approximately the same extent; however, large differences between the degree of stabilization of rA–rU₂ and rI-rC helices are observed when the substituents R₁, R₂, and R₃ are large hydrophobic groups. Similar results are also obtained for the spermidine series. Finally, differences in the interactions of the salts II and III with rA–rU₂ and rI–rC helices suggest that the latter helix is denser.     

Topography of nucleic acid helices in solutions. II. Structure of the double-stranded rA-rU, rI-rC, acid rA, and the triple-stranded rA-rU2 and rA-rI2 helices

Information concerning the structures of rA–rU, rA–rU₂ rI–rC, rA–rI₂, and acid rA helices in solutions is reported. Through the use of diquaternary ammonium salts of the general structure, \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R}_1 {\rm R}_2 {\rm R}_3 \mathop {\rm N}\limits^ + ({\rm CH}_2 )n\mathop {\rm N}\limits^ + {\rm R}_1 {\rm R}_2 {\rm R}_3 \cdot 2{\rm Br}^ - $\end{document} (I), it is shown that (1) the distances between adjacent negatively charged oxygen atoms on the helix increases in the following order rA–rI₂ < rI–rC < rA–rU ? rA–rU₂; (2) the density of the helices increases in the order. rA–rI₂ < rA–rU < rA–rU₂ < rI–rC; (3) there is a large hydrophobia site in rA–rI₂ and possibly also in rA–rU, rA–rU₂, and rI–rC helices; (4) the results of the interactions between the salts of type I and the helices may be formulated in semi-quantitative terms by the use of two parameters, α, and β which are shown to be related to the charge separation and the density of the helices, respectively; (5) the studies in solutions compare favorably with the x-ray studies on the fibers; and (6) the acid rA helix differs significantly from the other helices by the fact that the electrostatic interstrand interactions between the negatively charged oxygen atom of a phosphate group and the positively charged 10-amino group of adenine contribute significantly to the stabilization of the helix, and thus it is found that the presence of the salts, I, leads to a significant destabilization of the acid rA helix.     

Effects of β-alanine supplementation on the onset of neuromuscular fatigue and ventilatory threshold in women

Summary. This study examined the effects of 28 days of β-alanine supplementation on the physical working capacity at fatigue threshold (PWC_FT), ventilatory threshold (VT), maximal oxygen consumption ( O_2-MAX), and time-to-exhaustion (TTE) in women. Twenty-two women (age ± SD 27.4 ± 6.1 yrs) participated and were randomly assigned to either the β-alanine (CarnoSyn™) or Placebo (PL) group. Before (pre) and after (post) the supplementation period, participants performed a continuous, incremental cycle ergometry test to exhaustion to determine the PWC_FT, VT, O_2-MAX, and TTE. There was a 13.9, 12.6 and 2.5% increase (p < 0.05) in VT, PWC_FT, and TTE, respectively, for the β-alanine group, with no changes in the PL (p > 0.05). There were no changes for O_2-MAX (p > 0.05) in either group. Results of this study indicate that β-alanine supplementation delays the onset of neuromuscular fatigue (PWC_FT) and the ventilatory threshold (VT) at submaximal workloads, and increase in TTE during maximal cycle ergometry performance. However, β-alanine supplementation did not affect maximal aerobic power ( O_2-MAX). In conclusion, β-alanine supplementation appears to improve submaximal cycle ergometry performance and TTE in young women, perhaps as a result of an increased buffering capacity due to elevated muscle carnosine concentrations.     

Energy requirements of Adélie penguin (Pygoscelis adeliae) chicks

Summary The energy requirements of Adélie penguin (Pygoscelis adeliae) chicks were analysed with respect to body mass (W, 0.145–3.35 kg, n=36) and various forms of activity (lying, standing, minor activity, locomotion, walking on a treadmill). Direct respirometry was used to measure O₂ consumption ( ) and CO₂ production. Heart rate (HR, bpm) was recorded from the ECG obtained by both externally attached electrodes and implantable HR-transmitters. The parameters measured were not affected by hand-rearing of the chicks or by implanting transmitters. HR measured in the laboratory and in the field were comparable. Oxygen uptake ranged from in lying chicks to at maximal activity, RQ=0.76. Metabolic rate in small wild chicks (0.14–0.38 kg) was not affected by time of day, nor was their feeding frequency in the colony (Dec 20–21). Regressions of HR on were highly significant (p< 0.0001) in transmitter implanted chicks (n=4), and two relationships are proposed for the pooled data, one for minor activities ( ), and one for walking ( ). Oxygen consumption, mass of the chick (2–3 kg), and duration of walking (T, s) were related as , whereas mass-specific O₂ consumption was related to walking speed (S, m·s^-1) as .Abbreviations bpm beats per minute - D distance walked (m) - ECG electrocardiogram - HR heart rate (bpm) - ns number of steps - RQ respiratory quotient - S walking speed (m·s^-1) - T time walked (s) - W body mass (kg)     

Respiratory evaporation in panting fowl: Partition between the respiratory and buccopharyngeal pumps

Summary Ventilation (V) and respiratory water loss were measured in domestic fowlGallus gallus subjected to raised environmental temperatures (33±2°C) and breathing air, 8% O₂ in N₂, 3% CO₂ in air or 5% CO₂ in air. Birds breathing air underwent an 18.6-fold increase in respiratory frequency and a 5-fold reduction in tidal volume and panting was accompanied by vigorous gular flutter. Hypoxic and hypercapnic birds breathed more slowly and deeply and gular flutter was strongly inhibited. The ratio was similar to that predicted on the basis of the measured ventilation assuming saturation of expired gas at measured gular mucosal temperature in hypoxic and hypercapnic birds but 54% greater than the predicted value in birds panting in air. It is concluded that the excess water loss during normal panting results from tidal airflow generated independently by the buccopharyngeal pump and that buccopharyngeal ventilation is equivalent to 54% of the respiratory ventilation.     

Modellierung der enzymatischen Cellobiosehydrolyse – Vergleich linearer und nichtlinearer Parameterbestimmung

Experimental kinetic data (initial rate and high conversion) on the hydrolysis of cellobiose by 1,4-β-glucosidace (Gliocladium sp.) have been analysed and a competitive inhibition by glucose has been proposed. The determination of kinetic parameters from integral data is based upon algorithms for non-linear optimization and numerical integration. The values of kinetic constants \documentclass{article}\pagestyle{empty}\begin{document}$(v_{\max } = 1.02\frac{{\mu {\rm M}_{{\rm glucose}} }}{{{\rm mg}_{{\rm protein}} \cdot \min }},K_M = 2.6{\rm mM/l, and }K_P = 1.2{\rm mM/l)}$\end{document} agree well with the initialrate results. An important distinction is the confidence limit of parameters. Linear regression analysis shows a virtual accuracy and can lead to wrong conclusions.     

Effects of rheological properties and mass transfer on plant cell bioreactor performance: production of tropane alkaloids

Volumetric mass transfer coefficients, K(L)a were measured over an aeration rate range from 0.1 to 1.0 vvm in a 1.2-L draft-tube-type airlift bioreactor for different Datura stramonium cell concentrations and correlated with superficial air velocity and rheological properties of the cell suspension. The measured K(L)a values (17-40 h(-1)) for a cell volume fraction of 0.2 (v/v) were approximately 2 times higher than those for the highest cell concentrations tested (cell volume fraction 0.7-0.8 v/v). Cell suspensions exhibited yield stress and pseudoplastic behavior. This behavior was described by the Casson model. The estimated yield stress values depended upon cell concentration with an exponent of 4.0. An empirical correlation based on the data for plant cell suspensions exhibiting yield stress was developed in order to determine aeration strategy for the plant cell cultivation in draft-tube-type airlift bioreactors: \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm K}_{\rm L} {\rm a} = {\rm A}({\rm U}_{{\rm gr}});{0.3} ({\rm \eta }_{{\rm eff}});{ - 0.4} $$\end{document} Aeration rates above 1.0 vvm caused a significant drop in cell yield and product content. Maximum growth and production were obtained at 0.6 vvm aeration. The cell and product yields obtained at 1.7 vvm were 2.8 times lower than the maximum values (25 g cell DW/L and 73.8 mg tropane alkaloid/L). The effects of the increased aeration rates on cell yield were also evaluated in terms of Reynolds stress. It was found that there was a relation between cell damage and the estimated Reynolds stress. The Reynolds stress estimated for the same aeration rate decreased with increasing cell concentration, suggesting that cells in the cultures at low cell concentrations are subjected to hydrodynamic damage. In the experiments with the cell cultures having a cell concentration of 0.3 (v/v), approximately 70% reduction in cell concentration was observed when the Reynolds stress was increased from 10 to 50 dyn/cm(2). (c) 1993 John Wiley & Sons, Inc.     

Using light as a lure is an efficient predatory strategy in <Emphasis Type="Italic">Arachnocampa flava,</Emphasis> an Australian glowworm

Trap-building, sit-and-wait predators such as spiders, flies and antlions tend to have low standard metabolic rates (SMRs) but potentially high metabolic costs of trap construction. Members of the genus Arachnocampa (glowworms) use an unusual predatory strategy: larvae bioluminesce to lure positively phototropic insects into their adhesive webs. We investigated the metabolic costs associated with bioluminescence and web maintenance in larval Arachnocampa flava. The mean rate of CO₂ production ([(V)\dot] \dot{V}CO₂) during continuous bioluminescence was 4.38 μl h⁻¹ ± 0.78 (SEM). The mean [(V)\dot] \dot{V}CO₂ of inactive, non-bioluminescing larvae was 3.49 ± 0.35 μl h⁻¹. The mean [(V)\dot] \dot{V}CO₂ during web maintenance when not bioluminescencing was 8.95 ± 1.78 μl h⁻¹, a value significantly lower than that measured during trap construction by other predatory arthropods. These results indicate that bioluminescence itself is not energetically expensive, in accordance with our prediction that a high cost of bioluminescence would render the Arachnocampa sit-and-lure predatory strategy inefficient. In laboratory experiments, both elevated feeding rates and daily web removal caused an increase in bioluminescent output. Thus, larvae increase their investment in light output when food is plentiful or when stressed through having to rebuild their webs. As light production is efficient and the cost of web maintenance is relatively low, the energetic returns associated with continuing to glow may outweigh the costs of continuing to attract prey.