Average shear rate in three pneumatic bioreactors

A method proposed in recent literature was applied to evaluate the average shear rate ( [(g)\dot]_av ) \left( {\dot{\gamma }_{\rm av} } \right) in three pneumatic bioreactors of 5-dm³ working volume: bubble column, split airlift, and concentric-tube airlift. The volumetric oxygen transfer coefficient (k _L a) is the appropriate characteristic parameter to assess the average shear rate ( [(g)\dot]_av ) \left( {\dot{\gamma }_{\rm av} } \right) in this methodology. Correlations for [(g)\dot]_av \dot{\gamma }_{\rm av} as a function of superficial gas velocity in the riser region (U _GR) and rheological fluid properties (consistency index, K, and flow index, n) were obtained for each model of pneumatic bioreactor studied. The [(g)\dot]_av \dot{\gamma }_{\rm av} values estimated by the proposed methodology lay within the range of values calculated by classical correlations. The proposed correlations were utilized to predict the [(g)\dot]_av \dot{\gamma }_{\rm av} during the Streptomyces clavuligerus cultivations carried out at the same specific air flow rate (3.5 vvm) in the different types of pneumatic bioreactors. The lowest values of [(g)\dot]_av \dot{\gamma }_{\rm av} related to the highest values of consistency index (K) were found for the bubble column bioreactor, and the highest values of [(g)\dot]_av \dot{\gamma }_{\rm av} related to the lowest values of K were found for the concentric-tube airlift bioreactor. Intermediate values were found for the split airlift bioreactor. The results showed that high [(g)\dot]_av \dot{\gamma }_{\rm av} values affect the structural health of the mycelia by the rupture of the hipha.     

Host-Guest Chemistry and Chemical Sensors: FT-IR-Analysis and Spectra Simulation of CDCl<Subscript>3</Subscript> Inclusion

Host-guest principles are put into action advantageously by cyclodextrins that give remarkable sensor responses to halogenated hydrocarbons on mass-sensitive devices such as QMB (quartz micro balance) and SAW (surface acoustic wave) resonators. Modifications of the structure can tune the compound to different analytes and molecular modeling allows us to understand and predict specific host-guest interactions. The FT-IR analysis of CDCl₃, incorporated into a partially methylated cyclodextrine, yields an astonishingly strong band shift of about 50 cm^-1 to lower wave numbers, in contrast to the permethylated product that shows a displaced band of 10 cm^-1 for the C-D stretching vibration. The explanation can be given by semiempirical methods and force field calculations. Two CDCl₃ binding sites are revealed, one being a multicentered inclusion ([(n)\tilde] ~ 2195  cm^-1{\tilde\nu}\sim 2195\;cm^{-1} of CDCl₃ at the upper rim of the #-cyclodextrine cone, whereas the other is incorporated within the cavity ([(n)\tilde] ~ 2240  cm^-1{\tilde\nu}\sim 2240\;cm^{-1}.     

HNCA-TOCSY-CANH experiments with alternate <Superscript>13</Superscript>C-<Superscript>12</Superscript>C labeling: a set of 3D experiment with unique supra-sequential information for mainchain resonance assignment

Described here is a set of three-dimensional (3D) NMR experiments that rely on CACA-TOCSY magnetization transfer via the weak ³ \textJ_{\textCa\textCa} ^{ 3} {\text{J}}_{{{\text{C}}\alpha {\text{C}}\alpha }} coupling. These pulse sequences, which resemble recently described ¹³C detected CACA-TOCSY (Takeuchi et al. 2010) experiments, are recorded in ¹H₂O, and use ¹H excitation and detection. These experiments require alternate ¹³C-¹²C labeling together with perdeuteration, which allows utilizing the small ³ \textJ_{\textCa\textCa} ^{ 3} {\text{J}}_{{{\text{C}}\alpha {\text{C}}\alpha }} scalar coupling that is otherwise masked by the stronger ¹J_CC couplings in uniformly ¹³C labeled samples. These new experiments provide a unique assignment ladder-mark that yields bidirectional supra-sequential information and can readily straddle proline residues. Unlike the conventional HNCA experiment, which contains only sequential information to the ^{1 3} \textC^a ^{ 1 3} {\text{C}}^{\alpha } of the preceding residue, the 3D hnCA-TOCSY-caNH experiment can yield sequential correlations to alpha carbons in positions i−1, i + 1 and i−2. Furthermore, the 3D hNca-TOCSY-caNH and Hnca-TOCSY-caNH experiments, which share the same magnetization pathway but use a different chemical shift encoding, directly couple the ¹⁵N-¹H spin pair of residue i to adjacent amide protons and nitrogens at positions i−2, i−1, i + 1 and i + 2, respectively. These new experimental features make protein backbone assignments more robust by reducing the degeneracy problem associated with the conventional 3D NMR experiments.     

Transition from octahedral to tetrahedral geometry causes the activation or inhibition by Zn<Superscript>2+</Superscript> of <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> phosphorylcholine phosphatase

Pseudomonas aeruginosa phosphorylcholine phosphatase (PchP) catalyzes the hydrolysis of phosphorylcholine, which is produced by the action of hemolytic phospholipase C on phosphatidylcholine or sphyngomielin, to generate choline and inorganic phosphate. Among divalent cations, its activity is dependent on Mg²⁺ or Zn²⁺. Mg²⁺ produced identical activation at pH 5.0 and 7.4, but Zn²⁺ was an activator at pH 5.0 and became an inhibitor at pH 7.4. At this higher pH, very low concentrations of Zn²⁺ inhibited enzymatic activity even in the presence of saturating Mg²⁺ concentrations. Considering experimental and theoretical physicochemical calculations performed by different authors, we conclude that at pH 5.0, Mg²⁺ and Zn²⁺ are hexacoordinated in an octahedral arrangement in the PchP active site. At pH 7.4, Mg²⁺ conserves the octahedral coordination maintaining enzymatic activity. The inhibition produced by Zn²⁺ at 7.4 is interpreted as a change from octahedral to tetrahedral coordination geometry which is produced by hydrolysis of the [ \textZn ²⁺ \textL ₂ ^{- 1} \textL ₂⁰ ( \textH ₂ \textO ) ₂ ] \left[ {{\text{Zn}}^{ 2+ } {\text{L}}_{ 2}^{ - 1} {\text{L}}_{ 2}^{0} \left( {{\text{H}}_{ 2} {\text{O}}} \right)_{ 2} } \right] complex.     

Broadband <Superscript>15</Superscript>N–<Superscript>13</Superscript>C dipolar recoupling via symmetry-based RF pulse schemes at high MAS frequencies

An approach for generating efficient RN_n^{n_S, n_k} {\rm{RN}}_{n}^{\nu_{\rm{S}}, {\nu_{\rm{k}}}} symmetry-based dual channel RF pulse schemes for γ-encoded broadband ¹⁵N–¹³C dipolar recoupling at high magic angle spinning frequencies is presented. The method involves the numerical optimisation of the RF phase-modulation profile of the basic “R” element so as to obtain heteronuclear double quantum dipolar recoupling sequences with satisfactory magnetisation transfer characteristics. The basic “R” element was implemented as a sandwich of a small number of short pulses of equal duration with each pulse characterised by a RF phase and amplitude values. The performance characteristics of the sequences were evaluated via numerical simulations and ¹⁵N–¹³C chemical shift correlation experiments. Employing such ¹³C–¹⁵N double-quantum recoupling sequences and the multiple receiver capabilities available in the current generation of NMR spectrometers, the possibility to simultaneously acquire 3D NCC and CNH chemical shift correlation spectra is also demonstrated.     

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.     

Expression,subcellular localization,and <Emphasis Type="Italic">cis</Emphasis>-regulatory structure of duplicated phytoene synthase genes in melon (<Emphasis Type="Italic">Cucumis melo</Emphasis> L.)

The emission of molecular iodine (I₂) from the stipe, the meristematic area and the distal blade of the brown macroalga Laminaria digitata (Hudson) Lamouroux (Phaeophyceae) was monitored under low light and dark conditions. Photosynthetic parameters were determined to investigate both the extent of stress experienced by different thallus parts and the effects of emersion on photosynthesis. Immediately after air exposure, intense I₂ emission was detectable from all thallus parts. I₂ emission declined continuously over a period of 180 min following the initial burst, but was not affected by the light regime. The total number of mole of I₂ emitted by stipes was approximately 10 times higher than those emitted from other thallus parts. Initial I₂ emission rates (measured within 30 min of exposure to air) were highest for stipes (median values: 2,999 and 5,222 pmol g⁻¹ dw min⁻¹ in low light and dark, respectively) and lower, by one order of magnitude, for meristematic regions and distal blades. After exposure to air for between 60 and 180 min, I₂ emission rates of all thallus parts were reduced by 70–80%. Air exposure resulted in a decrease of the maximum photosystem II (PSII) efficiency (F _v/F _m) by 3%, and in a 25–55% increase of the effective PSII quantum efficiency ( \Updelta F/F^￠_\textm \Updelta F/F^{\prime}_{\text{m}} ); this was caused by a higher fraction of open reaction centres (q_P), whereas the efficiency of the latter in capturing energy ( F^￠_\textv /F^￠_\textm F^{\prime}_{\text{v}} /F^{\prime}_{\text{m}} ) remained constant. The results indicate the presence of an iodine pool which is easily volatilised and depleted due to air exposure, even under apparently low stress conditions.     

Loss of ncm<Superscript>5</Superscript> and mcm<Superscript>5</Superscript> wobble uridine side chains results in an altered metabolic profile

Introduction

The Elongator complex, comprising six subunits (Elp1p-Elp6p), is required for formation of 5-carbamoylmethyl (ncm⁵) and 5-methoxycarbonylmethyl (mcm⁵) side chains on wobble uridines in 11 out of 42 tRNA species in Saccharomyces cerevisiae. Loss of these side chains reduces the efficiency of tRNA decoding during translation, resulting in pleiotropic phenotypes. Overexpression of hypomodified \( {\text {tRNA}_{{\rm s^{2} {\rm UUU}}}^{{\rm Lys}} , {\rm tRNA}_{{\rm s^{2} {\rm UUG}}}^{{\rm Gln }} \;{\rm and}\;{\rm tRNA}_{{\rm s^{2} {\rm UUC}}}^{{\rm Glu}}} \), which in wild-type strains are modified with mcm⁵s²U, partially suppress phenotypes of an elp3Δ strain.

Objectives

To identify metabolic alterations in an elp3Δ strain and elucidate whether these metabolic alterations are suppressed by overexpression of hypomodified \( {\text {tRNA}_{{\rm s^{2} {\rm UUU}}}^{{\rm Lys}} , {\rm tRNA}_{{\rm s^{2} {\rm UUG}}}^{{\rm Gln }} \;{\rm and}\;{\rm tRNA}_{{\rm s^{2} {\rm UUC}}}^{{\rm Glu}}} \).

Method

Metabolic profiles were obtained using untargeted GC-TOF-MS of a temperature-sensitive elp3Δ strain carrying either an empty low-copy vector, an empty high-copy vector, a low-copy vector harboring the wild-type ELP3 gene, or a high-copy vector overexpressing \( {\text {tRNA}_{{\rm s^{2} {\rm UUU}}}^{{\rm Lys}} , {\rm tRNA}_{{\rm s^{2} {\rm UUG}}}^{{\rm Gln }} \;{\rm and}\;{\rm tRNA}_{{\rm s^{2} {\rm UUC}}}^{{\rm Glu}}} \). The temperature sensitive elp3Δ strain derivatives were cultivated at permissive (30 °C) or semi-permissive (34 °C) growth conditions.

Results

Culturing an elp3Δ strain at 30 or 34 °C resulted in altered metabolism of 36 and 46 %, respectively, of all metabolites detected when compared to an elp3Δ strain carrying the wild-type ELP3 gene. Overexpression of hypomodified \( {\text {tRNA}_{{\rm s^{2} {\rm UUU}}}^{{\rm Lys}} , {\rm tRNA}_{{\rm s^{2} {\rm UUG}}}^{{\rm Gln }} \;{\rm and}\;{\rm tRNA}_{{\rm s^{2} {\rm UUC}}}^{{\rm Glu}}} \) suppressed a subset of the metabolic alterations observed in the elp3Δ strain.

Conclusion

Our results suggest that the presence of ncm⁵- and mcm⁵-side chains on wobble uridines in tRNA are important for metabolic homeostasis.

     

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.     

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.     

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.     

Applicability of <Emphasis Type="Italic">Penicillium</Emphasis><Emphasis Type="Italic">chrysogenum</Emphasis> rheological correlations to broths of other fungal strains

Existing correlations of Power law consistency index with Penicillium chrysogenum biomass concentration and morphology were revised using a microscope magnification of 50 times to characterize the latter, rather than the 80 times used previously. This allowed tests of the correlations on broths of Aspergillus oryzae and Aspergillus niger, which have such large mycelial sizes that a lower magnification is required for accurate morphological analysis. The new correlations were successful at predicting the rheology of A. oryzae broths but not A. niger broths, which may be because of a change in the exponent on the biomass concentration in the correlations for the latter. Because the mean maximum dimension of clumps is magnification independent, the preferred correlation was:

Nitrogen metabolism of asparagine and glutamate in Vero cells studied by <Superscript>1</Superscript>H/<Superscript>15</Superscript>N NMR spectroscopy

Glutamine-free culture of Vero cells has previously been shown to cause higher cell yield and lower ammonia accumulation than that in glutamine-containing culture. Nitrogen metabolism of asparagine and glutamate as glutamine replacer was studied here using nuclear magnetic resonance (NMR) spectroscopy. ¹⁵N-labelled glutamate or asparagine was added and their incorporation into nitrogenous metabolites was monitored by heteronuclear multiple bond coherence (HMBC) NMR spectroscopy. In cells incubated with l-[¹⁵N]glutamate, the ¹⁵N label was subsequently found in a number of metabolites including alanine, aspartate, proline, and an unidentified compound. No detectable signal occurred, indicating that glutamate was utilized by transamination rather than by oxidative deamination. In cells incubated with l-[2-¹⁵N]asparagine, the ¹⁵N label was subsequently found in aspartate, the amine group of glutamate/glutamine, and in two unidentified compounds. Incubation of cells with l-[4-¹⁵N]asparagine showed that the amide nitrogen of asparagine was predominantly transferred to glutamine amide. There was no detectable production of , showing that most of the asparagine amide was transaminated by asparagine synthetase rather than deaminated by asparaginase. Comparing with a glutamine-containing culture, the activities of phosphate-activated glutaminase (PAG), glutamate dehydrogenase (GDH) and alanine aminotransferase (ALT) decreased significantly and the activity of aspartate aminotransferase (AST) decreased slightly.     

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.     

<Emphasis Type="SmallCaps">l</Emphasis>-carnitine modulates blood platelet oxidative stress

The oxidative stress induced by acute exertion may interfere with blood platelet activation. The beneficial effect of l-carnitine (γ-trimethylamino-β-hydroxybutyric acid) on oxidative stress in blood platelets has not been fully investigated; however, different studies indicate that this compound modulates platelet functions. The aim of our study was to assess the effects of l-carnitine on platelet activation and oxidative/nitrative protein damage (determined by the levels of protein carbonyl groups, thiol groups, and 3-nitrotyrosine residues) in resting blood platelets or platelets treated with peroxynitrite (ONOO⁻, a strong physiological oxidant) in vitro. We also investigated the effects of l-carnitine on the level of platelet glutathione and on the formation of superoxide anion radicals ( O₂ ^{- ·} ) \left( {{\hbox{O}}_2^{ - \bullet }} \right) , lipid peroxidation measured by thiobarbituric acid reactive substances (TBARS) in blood platelets stimulated by thrombin (a strong physiological agonist), and platelet aggregation induced by adenosine diphosphate (a strong physiological stimulator). We have observed that carnitine decreases platelet activation (measured by platelet aggregation, the generation of O₂ ^{- ·} {\hbox{O}}_2^{ - \bullet } , and TBARS production). Moreover, our results in vitro demonstrate that carnitine may protect against oxidation of thiol groups induced by ONOO⁻. Thus, carnitine may have some protectory effects against oxidative changes induced in blood platelets.     

Electrostatic effect of surfactant molecules on bacteriochlorophyll a and carotenoid binding sites in the LH1 complex isolated from Rhodospirillum rubrum S1 probed by Stark spectroscopy

The LH1 complexes were isolated from the purple photosynthetic bacterium Rhodospirillum rubrum strain S1. They were initially solubilized using LDAO and then purified in the presence of Triton X-100. The purified complexes were then either used directly or following an exchange into LDAO. Stark spectroscopy was applied to probe the electrostatic field around the bacteriochlorophyll a (BChl a) and carotenoid binding sites in the LH1 complexes surrounded by these two different surfactant molecules. Polarizabilty change () and dipole moment change () upon photoexcitation were determined for the BChl a Q_y band. Both of these parameters show smaller values in the presence of LDAO than in Triton X-100. This indicates that polar detergent molecules, like LDAO, affect the electrostatic environment around BChl a, and modify the nonlinear optical parameters ( and values). The electrostatic field around the BChl a binding site, which is generated by the presence of LDAO, was determined to be |E _L | = ∼3.9 × 10⁵ [V/cm]. Interestingly, this kind of electrostatic effect was not observed for the carotenoid-binding site. The present study demonstrates a unique electrostatic interaction between the polar detergent molecules surrounding the LH1 complex and the Q_y absorption band of BChl a that is bound to the LH1 complex.     

Na<Superscript>+</Superscript> Modulates Anion Permeation and Block of P2X<Subscript>7</Subscript> Receptors from Mouse Parotid Glands

Experiments were conducted to test the hypothesis that aliphatic hydrocarbons bind to pockets/crevices of sodium (Na⁺) channels to cause action potential (AP) block. Aliphatic solutes exhibiting successively greater octanol/water partitition coefficients (K _ow) were studied. Each solute blocked Na⁺ channels. The 50% effective concentration (EC₅₀) to block APs could be mathematically predicted as a function of the solute’s properties. The solutes studied were methyl ethyl ketone (MEK), cyclohexanone, dichloromethane, chloroform and triethylamine (TriEA); the K _ow increased from MEK to TriEA. APs were recorded from frog nerves, and test solutes were added to Ringer’s solution bathing the nerve. When combined with EC₅₀s for solutes with log K _ows < 0.29 obtained previously, the solute EC₅₀s could be predicted as a function of the fractional molar volume (dV/dm = [dV/dn]/100), polarity (P) and the hydrogen bond acceptor basicity (β) by the following equation: Fluidity changes cannot explain the EC₅₀s. Each of the solutes blocks Na⁺ channels with little or no change in kinetics. Na⁺ channel block explains much of the EC₅₀ data. EC₅₀s are produced by a combination of effects including ion channel block, fluidity changes and osmotically induced structural changes. As the solute log K _ow increases to values near 1 or greater, Na⁺ channel block dominates in determining the EC₅₀. The results are consistent with the hypothesis that the solutes bind to channel crevices to cause Na⁺ channel and AP block.     

The effect of cold-induced increased metabolic rate on the rate of <Superscript>13</Superscript>C and <Superscript>15</Superscript>N incorporation in house sparrows (<Emphasis Type="Italic">Passer domesticus</Emphasis>)

Animals with high metabolic rates are believed to have high rates of carbon and nitrogen isotopic incorporation. We hypothesized that (1) chronic exposure to cold, and hence an increase in metabolic rate, would increase the rate of isotopic incorporation of both ¹³C and ¹⁵N into red blood cells; and (2) that the rate of isotopic incorporation into red blood cells would be allometrically related to body mass. Two groups of sparrows were chronically exposed to either 5 or 22°C and switched from a ¹³C-depleted C₃-plant diet to a more ¹³C-enriched C₄-plant one. We used respirometry to estimate the resting metabolic rate of birds exposed chronically to our two experimental temperatures. The allometric relationship between the rate of ¹³C incorporation into blood and body mass was determined from published data. The of birds at 5°C was 1.9 times higher than that of birds at 22°C. Chronic exposure to a low temperature did not have an effect on the rate of isotopic incorporation of ¹⁵N save for a very small effect on the incorporation of ¹³C. The isotopic incorporation rate of ¹³C was 1.5 times faster than that of ¹⁵N. The fractional rate of ¹³C incorporation into avian blood was allometrically related to body mass with an exponent similar to −1/4. We conclude that the relationship between metabolic rate and the rate of isotopic incorporation into an animal’s tissues is indirect. It is probably mediated by protein turnover and thus more complex than previous studies have assumed.     

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.