Investigating the effects of opioid drugs on electrocortical activity using wavelet transform

 Fetal electrocortical activity (ECoG) is characterized by two distinct patterns: HVSA (high voltage, slow activity) and LVFA (low voltage, fast activity). Using the wavelet transform (WT), we recently reported that the frequency characteristics of these two ECoG patterns undergo significant maturational changes prior to birth (Akay et al. 1994a). We now report that fetal ECoG can also be significantly affected by pharmacological agents. In this paper, we compared the effects of two opioid drugs (morphine and [D-Pen², D-Pen⁵]enkephalin, DPDPE) on fetal ECoG, using the chronically instrumented fetal lamb model. Morphine was infused intravenously (i.v.) at 2.5 mg/h, while DPDPE was infused into the lateral cerebroventricle (i.c.v.) at 30 μg/h. The ECoG was analyzed using WT. We performed multiresolution decomposition for four sets of parameters D _{2 j} where −1<j<−4. The four series WTs represent the detail signal bandwidths: (1) 16–32 Hz, (2) 8–16 Hz, (3) 4–8 Hz, (4) 2–4 Hz. The data were subjected to statistical analysis using the Kolmogorov–Smirnov (KS) test. Both morphine and DPDPE resulted in a significant increase in power in the first wavelet band, while power was reduced in the second, third and fourth wavelet bands. In addition, both drugs resulted in a disruption of the normal cyclic pattern between the two ECoG patterns. There was a difference in the time course of action between morphine and DPDPE. This is the first occasion in which continuous ECoG has been subjected to rigorous statistical analysis. The results suggest that the WT-KS method is most suitable for quantitating changes in the ECoG induced by pharmacological agents. Received: 21 January 1994/Accepted in revised form: 15 September 1994     

The effects of morphine on the relationship between fetal EEG, breathing and blood pressure signals using fast wavelet transform

In this study, we introduce the fast wavelet transform (WT) as a method for investigating the effects of morphine on the electroencephalogram (EEG), respiratory activity and blood pressure in fetal lambs. Morphine was infused intravenously at 25 mg/h. The EEG, respiratory activity and blood pressure signals were analyzed using WT. We performed wavelet decomposition for five sets of parameters D _2j where -1 < j 5. The five series WTs represent the detail signal bandwidths: 1, 16–32 Hz; 2, 8–16 Hz; 3, 4–8 Hz; 4, 2–4 Hz; 5, 1–2 Hz. Before injection of the high-dose morphine, power in the EEG was high in all six frequency bandwidths. The respiratory and blood pressure signals showed common frequency components with respect to time and were coincident with the low-voltage fast activity (LVFA) EEG signal. Respiratory activity was observed during only some of the LVFA periods, and was completely absent during high-voltage slow activity (HVSA) EEG. The respiratory signal showed dominant power in the fourth wavelet band, and less power in the third and fifth bands. The blood pressure signal was also characterized by dominant power in the fourth wavelet band. This power was significantly increased during periods of respiratory activity. There was a strong relationship between fetal EEG, blood pressure and breathing movements. However, the injection of high-dose morphine resulted in a disruption of the normal cyclic pattern between the two EEG states and a significant increase in power in the first wavelet band. In addition, the high-dose drug resulted in a significant increase in the power of respiratory signal in the fourth and fifth wavelet bands, while power was reduced in the third wavelet band. Breathing activity was also continuous after the drug. The high-dose morphine also caused a temporary power shift from the third wavelet band to the fourth wavelet band for the 30-min period after injection of drug. Finally, high-dose morphine completely destroyed the correlation between EEG, breathing and blood pressure signals.     

Regulation of breathing movements in fetal sheep by prostaglandin E2

In fetal sheep, plasma prostaglandin (PG) E2 concentrations are high, and fetal breathing movements (FBM) occur intermittently, primarily during low-voltage fast electrocortical activity (LVFA). There is evidence suggesting that prostaglandins, specifically PGE2, may regulate FBM. To define the physiological role of PGE2 in regulation of FBM, we infused meclofenamate (0.9 mg X kg-1 X h-1), a prostaglandin synthetase inhibitor, into six fetal sheep to suppress endogenous prostaglandin production. Afterward, PGE2 was added in mean doses of 9, 18, 36, and 90 ng X kg-1 X min-1. Meclofenamate decreased PGE2 concentrations and increased FBM, especially during high-voltage slow electrocortical activity (HVSA). Addition of PGE2 reversed the effects of meclofenamate, increasing PGE2 concentrations and decreasing FBM, especially during HVSA. The response to PGE2 was dose dependent; the overall incidence of FBM and incidences of FBM during HVSA and LVFA were inversely correlated with both the infused PGE2 dose and the mean PGE2 concentration. At higher doses of PGE2, FBM occurred intermittently and only during LVFA; thus PGE2 infusion restored the physiological pattern of FBM. These results indicate that PGE2 regulates FBM by inhibiting FBM during HVSA.     

Baseline EEG gamma activity and induced responses to facial stimuli during the formation of a visual cognitive set

The power spectra of cortical potentials of baseline activity during interstimulus intervals (4 s; Fourier transform in the frequency band of 1–60 Hz) and short-term (0.8 s) induced responses to facial stimuli (wavelet transform in the 15–60 Hz band) were assessed during the study of the visual cognitive set to facial expression. Significant differences between groups of subjects with different set plasticities were observed only at the set-testing stage. Estimation of short-term (0.8 s) induced responses of wavelet spectra in the group with the plastic set revealed an increase in the power (compared to the power of background activity) of the γ₂ band (41–60 Hz) in the temporal, central and occipital areas of the left hemisphere, whereas in the group with the rigid set these power spectra decreased. At the same time, the power in the γ₁ band (21–40 Hz) was significantly lower (at the same level with the rigid form), indicating the discrete nature and functional selectivity in the γ frequency band.     

Methane-Oxidizing Bacteria in a Finnish Raised Mire Complex: Effects of Site Fertility and Drainage

Methane-oxidizing bacteria (MOB) are the only biological sinks for methane (CH₄). Drainage of peatlands is known to decrease overall CH₄ emission, but the effect on MOB is unknown. The objective of this work was to characterize the MOB community and activity in two ecohydrologically different pristine peatland ecosystems, a fen and a bog, and their counterparts that were drained in 1961. Oligotrophic fens are groundwater-fed peatlands, but ombrotrophic bogs receive additional water and nutrients only from rainwater. The sites were sampled in August 2003 down to 10 cm below the water table (WT), and cores were divided into 10-cm subsamples. CH₄ oxidation was measured by gas chromatography (GC) to characterize MOB activity. The MOB community structure was characterized by polymerase chain reaction–denaturing gradient gel electrophoresis (DGGE) and sequencing methods using partial pmoA and mmoX genes. The highest CH₄ oxidation rates were measured from the subsamples 20–30 and 30–40 cm above WT at the pristine oligotrophic fen (12.7 and 10.5 μmol CH₄ dm⁻³ h⁻¹, respectively), but the rates decreased to almost zero in the vicinity of WT. In the pristine ombrotrophic bog, the highest oxidation rate at 0–10 cm was lower than in the fen (8.10 μmol CH₄ dm⁻³ h⁻¹), but in contrast to the fen, oxidation rates of 4.5 μmol CH₄ dm⁻³ h⁻¹ were observed at WT and 10 cm below WT. Drainage reduced the CH₄ oxidation rates to maximum values of 1.67 and 5.77 μmol CH₄ dm⁻³ h⁻¹ at 30–40 and 20–30 cm of the fen and bog site, respectively. From the total of 13 pmoA-derived DGGE bands found in the study, 11, 3, 6, and 2 were observed in the pristine fen and bog and their drained counterparts, respectively. According to the nonmetric multidimensional scaling of the DGGE banding pattern, the MOB community of the pristine fen differed from the other sites. The majority of partial pmoA sequences belonged to type I MOB, whereas the partial mmoX bands that were observed only in the bog sites formed a distinct group relating more to type II MOB. This study indicates that fen and bog ecosystems differ in MOB activity and community structure, and both these factors are affected by drainage.     

Physical and physiological aspects of gear efficiency in North Sea brown shrimp fisheries

In search of means to reduce the by-catch of juvenile flatfish in the shrimp fishery, vibrations and changes in current velocity caused by shrimp trawls were investigated in the field and in the laboratory. Buried as well as emerged shrimps (Crangon crangon) exhibit tailflips 5–10 cm before being touched by the rollers of a shrimp gear approaching them at a speed of 0.5 m·sec⁻¹, as was revealed by slow motion video recordings in aquaria under artificial light. Hence, the signal effective in triggering escape must be attenuated strongly with increasing distance. Sediment vibration, commonly assumed to be an important signal in triggering escape of shrimps, was found to decrease by a factor 100·m⁻¹. Signals from the rollers of a commercial shrimp gear in operation (towing speed 1 m·sec⁻¹) were directly recorded with an accelerometer. Their frequency ranged from 50 to 500 Hz and reached an acceleration of 40 m·sec⁻² on soft bottom or up to 100 m·sec⁻² on hard substrate. Accelerometers, which had been buried right at the surface of a tidal sand flat during low tide, produced only one sharp signal of 100 Hz with an acceleration of 24 m·sec⁻², when a shrimp gear swept them on the submerged tidal flats. However, in aquaria short sinusoidal signals (<5 m·sec⁻²; 20 to 300 Hz) made buried shrimps and flatfish (Pleuronectes platessa, Solea solea, Microstomus kitt) hide rather than flee. The vibrations recorded directly at the rollers and the underlying jolting movements of the rollers induce corresponding pulses in the water surrounding the rollers in a layer of approximately 10–15 cm. Similar water displacement of high acceleration was experimentally produced by a spring loaded transparent lucite piston (7 cm in diameter) fitted to an accelerometer. Accelerating this piston (12–116 m·sec⁻², 50–200 Hz range) from 5 cm above towards the shrimp produced escape responses in up to 94% of the tests. Arthropods are known to perceive medium displacement rather than pressure. Hence, strong and rapidly rising water currents caused by the rollers rather than sediment vibration are assumed to mainly trigger the escape reaction, which makesCrangon accessible to the gear.     

Enhancement of susceptivity to photoinhibition and photooxidation in rice chlorophyll <Emphasis Type="Italic">b</Emphasis>-less mutants

Two rice chlorophyll (Chl) b-less mutants (VG28-1, VG30-5) and the respective wild type (WT) plant (cv. Zhonghua No. 11) were analyzed for the changes in Chl fluorescence parameters, xanthophyll cycle pool, and its de-epoxidation state under exposure to strong irradiance, SI (1 700 μmol m⁻² s⁻¹). We also examined alterations in the chloroplast ultrastructure of the mutants induced by methyl viologen (MV) photooxidation. During HI (0–3.5 h), the photoinactivation of photosystem 2 (PS2) appeared earlier and more severely in Chl b-less mutants than in the WT. The decreases in maximal photochemical efficiency of PS2 in the dark (F_v/F_m), quantum efficiency of PS2 electron transport (Φ_PS2), photochemical quenching (q_P), as well as rate of photochemistry (P_rate), and the increases in de-epoxidation state (DES) and rate of thermal dissipation of excitation energy (D_rate) were significantly greater in Chl b-mutants compared with the WT plant. A relatively larger xanthophyll pool and 78–83 % conversion of violaxanthin into antheraxanthin and zeaxanthin in the mutants after 3.5 h of HI was accompanied with a high ratio of inactive/total PS2 (0.55–0.73) and high 1–q_P (0.57–0.68) which showed that the activities of the xanthophyll cycle were probably insufficient to protect the photosynthetic apparatus against photoinhibition. No apparent difference of chloroplast ultrastructure was found between Chl b-less mutants and WT plants grown under low, LI (180 μmol m⁻² s⁻¹) and high, HI (700 μmol m⁻² s⁻¹) irradiance. However, swollen chloroplasts and slight dilation of thylakoids occurred in both mutants and the WT grown under LI followed by MV treatment. These typical symptoms of photooxidative damage were aggravated as plants were exposed to HI. Distorted and loose scattered thylakoids were observed in particular in the Chl b-less mutants. A greater extent of photoinhibition and photooxidation in these mutants indicated that the susceptibility to HI and oxidative stresses was enhanced in the photosynthetic apparatus without Chl b most likely as a consequence of a smaller antenna size.     

Differential effects of aging on EEG after baclofen administration

Baclofen is a selective gamma-aminobutyric acid (GABA) type B agonist that may have important medicinal uses, such as in analgesics and drug addiction treatment. In addition, evidence is accumulating that suggests GABAergic-mediated neurotransmission is altered during aging. This study investigated whether baclofen administration (5 mg kg⁻¹) induces differential effects on cortical electrical activity with age. Electroencephalograms (EEGs) were recorded from young (3–4 months) and aged (15–17 months) rats, and both the absolute and relative powers in five frequency bands (delta: 2–4 Hz; theta: 4–8 Hz; alpha: 8–12 Hz; beta: 12–20 Hz; gamma: 20–100 Hz) were analyzed. Before administration of baclofen, we found that the EEG relative power in the beta band was higher in the aged than that in the young rats. After administration of baclofen, there was a slower increase in the relative power in the delta band in the aged than that in the young rats. Moreover, there was no significant difference between the two age groups in absolute power in any frequency band. These findings indicate that baclofen treatment appears to differentially modify cortical EEG activity as a function of age. Our data further elucidate the relationship between GABA_B receptor-mediated neurotransmission and aging.     

Temperature and the temporal resolving power of fly photoreceptors

A hot head gives an insect a clearer view of a moving world because warming reduces motion blur by accelerating photoreceptor responses. Over a natural temperature range, 19–34 °C, the speed of response of blowfly (Calliphora vicina) photoreceptors more than doubles, to produce the fastest functional responses recorded from an ocular photoreceptor. This acceleration increases temporal resolving power, as indicated by the corner frequency of the response power spectrum. When light adapted, the corner frequency increases from 53 Hz to 119 Hz with a Q ₁₀ of 1.9, and when dark adapted from 8 Hz to 32 Hz with a Q ₁₀ of 3.0. Temperature sensitivity originates in the phototransduction cascade, and is associated with signal amplification. The temperature sensitivity of photoreceptors must be taken into account when studying the mechanisms, function and ecology of vision, and gives a distinct advantage to insects that thermoregulate. Accepted: 2 February 2000     

Modest increase in temperature affects ODC activity in L929 cells: low-level radiofrequency radiation does not

The effects of low-level radiofrequency (RF) radiation and elevated temperature on ornithine decarboxylase (ODC) activity were investigated in murine L929 fibroblasts. The cells were exposed at 900 MHz either to a pulse-modulated (pulse frequency 217 Hz; GSM-type modulation) or a continuous wave signal at specific absorption rate (SAR) levels of 0.2 W kg⁻¹ (0.1–0.3 W kg⁻¹) and 0.4 W kg⁻¹ (0.3–0.5 W kg⁻¹) for 2, 8, or 24 h. RF radiation did not affect cellular ODC activity. However, a slight increase in temperature (0.8–0.9°C) in the exposure system lead to decreased ODC activity in cell cultures. This was verified by tests in which cells were exposed to different temperatures in incubators. The results show that ODC activity is sensitive to small temperature differences in cell cultures. Hence, a precise temperature control in cellular ODC activity studies is needed.     

Strong coupling effects during <Emphasis Type="Italic">X</Emphasis>-pulse CPMG experiments recorded on heteronuclear <Emphasis Type="Italic">ABX</Emphasis> spin systems: artifacts and a simple solution

Simulation and experiment have been used to establish that significant artifacts can be generated in X-pulse CPMG relaxation dispersion experiments recorded on heteronuclear ABX spin-systems, such as ¹³C _i –¹³C _j –¹H, where ¹³C _i and ¹³C _j are strongly coupled. A qualitative explanation of the origin of these artifacts is presented along with a simple method to significantly reduce them. An application to the measurement of ¹H CPMG relaxation dispersion profiles in an HIV-2 TAR RNA molecule where all ribose sugars are protonated at the 2′ position, deuterated at all other sugar positions and ¹³C labeled at all sugar carbons is presented to illustrate the problems that strong ¹³C–¹³C coupling introduces and a simple solution is proposed.     

Enantioselective biocatalytic hydrolysis of (<Emphasis Type="Italic">R</Emphasis>,<Emphasis Type="Italic">S</Emphasis>)-mandelonitrile for production of (<Emphasis Type="Italic">R</Emphasis>)-(−)-mandelic acid by a newly isolated mutant strain

(R)-(−)-Mandelic acid (R-MA) is an important intermediate with broad uses. Recently, R-MA production using nitrilase has been gaining more and more attention due to its higher productivity and enantioselectivity. In this work, a new bacterium WT10, which exhibited favorable nitrilase activity and excellent enantioselectivity for production of R-MA by enantioselective biocatalytic hydrolysis of (R,S)-mandelonitrile, was isolated and identified as a strain of Alcaligenes faecalis. In order to improve its nitrilase activity for industrial application, the wild-type strain WT10 was further subjected to mutagenesis using a combined LiCl–ultraviolet irradiation and low energy N⁺ ion beams implantation technique. A valuable mutant strain A. faecalis ZJUTB10 was obtained. The nitrilase specific activity of the mutant strain was greatly improved up to 350.8 U g⁻¹, in comparison with wild-type strain WT10 of 53.09 U g⁻¹. The reaction conditions for R-MA production by mutant strain A. faecalis ZJUTB10 were also optimized. Nitrilase activity in mutant strain showed a broad pH optimum at pH 7.7–8.5. The optimal temperature was 35°C. The highest production rate reached 9.3 mmol h⁻¹ g⁻¹. The results showed that mutant strain A. faecalis ZJUTB10 was a new candidate for efficient R-MA production from (R,S)-mandelonitrile and could potentially be used in industrial production.     

Effect of Novel Amino Acids and Dipeptides Substituted 3-Morpholino Arecoline Derivatives as Muscarinic Receptor 1 Agonists in Alzheimer’s Dementia Models

A series of novel, potent and selective muscarinic receptor 1 agonists (M1 receptor agonists) that employ a key N-substituted morpholine arecoline moiety has been synthesized as part of research effort for the therapy of Alzheimer’s diseases. The ester group of arecoline (which is reported as mucarinic agonist) has been replaced by N-substituted morpholine ring. The structure activity relationship reveals that the increase in lipophilic carbon chain on the nitrogen atom of the morpholine ring increases the affinity of M1 receptor. In the present study, we are reporting N-amino acid substituted 9(a–k) and dipeptides substituted 10(a–j) and 11(a–j) morpholino arecoline derivatives, along with their in vitro muscarinic binding studies by using [³H]QNB and also in vivo evaluation of memory and learning in male Wistar rats (passive avoidance test plus maze studies) as M1 receptor agonist. Some molecules from the dipeptide series (10b, 10c and 10j) showed potent M1 receptor agonist activity. Other derivatives also showed considerable M1 receptor binding affinity.     

Induction of emotional states by reading aloud texts with various emotional valences and changes in the EEG power in the β and γ frequency bands

The EEG power in the β₁, β₂, and γ frequency bands during reading according to the method of “self-regulatory utterance” was compared in subjects reading aloud emotionally neutral business texts related to an unknown field of activity, fiction texts with clear positive or negative valences or personally important autobiographic texts with similar emotional valences. Two groups of subjects participated in the study: students training to be actors (N = 22) and students with other specializations (N = 23). We observed higher values of the EEG power in the γ (30–40 Hz) and β₂ (18.5–29.5 Hz) frequency bands when comparing the states during reading of emotionally positive and emotionally negative fiction texts and personally important texts. These data are similar to our previous studies with the use of techniques that apply internal induction of positive or negative emotions without speech, in different groups of subjects. Internal induction of positive emotions was associated with an increase in the EEG power in these bands compared to the performance of an emotionally neutral task, whereas induction of negative emotions resulted in a decrease in the EEG power.     

Quantification of water and biomass in small colony variant PAO1 biofilms by confocal Raman microspectroscopy

The Raman spectra, water content, and biomass density of wild-type (WT) Pseudomonas aeruginosa PAO1, small colony variant (SCV) PAO1, and Pseudoalteromonas sp. NCIMB 2021 biofilms were compared in order to determine their variation with strain and species. Living, fully submerged biofilms were analyzed in situ by confocal Raman microspectroscopy for up to 2 weeks. Water to biomass ratios (W/BRs), which are the ratios of the O–H stretching vibration of water at 3,450 cm⁻¹ to the C–H stretching band characteristic of biomass at 2,950 cm⁻¹, were used to estimate the biomass density and cell density by comparison with W/BRs of protein solutions and bacterial suspensions, respectively, on calibration curves. The hydration within SCV biofilm colonies was extremely heterogeneous whereas W/BRs were generally constant in young WT biofilm colonies. The mean biomass in biofilm colonies of WT or colony cores of SCV was typically equivalent to 16% to 27% protein (w/v), but was 10% or less for NCIMB 2021. The corresponding cell densities were 7.5 to >10 × 10¹⁰ cfu mL⁻¹ for SCV, while the maximum cell density for NCIMB biofilms was 2.8 × 10¹⁰ cfu mL⁻¹.     

Electroencephalograms of patients with initial signs of depression: Independent component analysis

Independent component analysis (ICA) of 19-channel background EEG was performed in 111 patients with the early signs of depressive disorders and in 526 healthy subjects. The power spectra of the independent components were compared in the depressive patients and in healthy subjects at the eyes closed and eyes opened states. Statistically significant differences between the groups were detected in three frequency bands: θ (4–7.5 Hz), α (7.5–14 Hz), and β (14–20 Hz). Increased θ and α activities in parietal and occipital derivations of depressive patients may have been caused by a reduced cortical activity in the projection of these derivation. Diffuse enhancement of the β activity may be correlated with anxiety symptoms that are pronounced in the clinical picture of depressive disorders at early stages of the disease. ICA used to compare quantitative EEG parameters in different groups of patients and in healthy persons makes it possible to localize the differences more accurately than the traditional analysis of EEG spectra.     

A new manganese superoxide dismutase identified from Beauveria bassiana enhances virulence and stress tolerance when overexpressed in the fungal pathogen

A superoxide dismutase (SOD) was characterized from Beauveria bassiana, a fungal entomopathogen widely applied to insect control. This 209-aa enzyme (BbSod2) showed no more than 71% sequence identity to other fungal Mn-SODs, sharing all conserved residues with the Mn-SOD family and lacking a mitochondrial signal. The SOD activity of purified BbSod2 was significantly elevated by Mn²⁺, suppressed by Cu²⁺ and Zn²⁺ but inhibited by Fe³⁺. Overexpressing the enzyme in a BbSod2-absent B. bassiana strain enhanced its SOD activity (107.2 ± 6.1 U mg⁻¹ protein) by 4–10-fold in different transformants analyzed. The best BbSod2-transformed strain with the SOD activity of 1,157.9 ± 74.7 U mg⁻¹ was 93% and 61% more tolerant to superoxide-generating menadione in both colony growth (EC₅₀ = 2.41 ± 0.03 versus 1.25 ± 0.01 mM) and conidial germination (EC₅₀ = 0.89 ± 0.06 versus 0.55 ± 0.07 mM), and 23% more tolerant to UV-B irradiation (LD₅₀ = 0.49 ± 0.02 versus 0.39 ± 0.01 J cm⁻²). Its virulence to Spodoptera litura larvae was enhanced by 26% [LT₅₀ = 4.5 (4.2–4.8) versus 5.7 (5.2–6.4) days]. Our study highlights for the first time that the Mn²⁺-cofactored, cytosolic BbSod2 contributes significantly to the virulence and stress tolerance of B. bassiana and reveals possible means to improving field persistence and efficacy of a fungal formulation by manipulating the antioxidant enzymes of a candidate strain.     

Energetic cost of hovering flight in a nectar-feeding bat measured with fast-response respirometry

Hover-feeding glossophagine bats provide, in addition to the hummingbirds, a second vertebrate model for the analysis of hovering flight based on metabolic measurement and aerodynamic theory. In this study, the power input of hovering Glossophaga soricina bats (11.9 g) was measured by standard respirometry and fast-response (<0.2 s) oxygen analysis. Bats needed 5–7 s after a rest-to-flight transition to return to a respiratory steady state. Therefore, only hovering events preceeded by a 7-s flight interval were evaluated. V˙_O2 during hovering fluctuated with a frequency of 3–5 Hz, which corresponded in frequency to the licking movement of the tongue. During hovering, bats often may have hypoventilated as indicated by reduced V˙_O2 and a respiratory exchange ratio (RER) well below the steady-state value of 1. Steady-state oxygen consumption (and derived power input) during hovering was estimated to be 27 (25–29) ml O₂ g⁻¹ h⁻¹ (158 W kg⁻¹ or 1.88 W) in the 11.9-g bats as indicated by three independent findings: (1) V˙_O2 was 26 ml O₂ g⁻¹ h⁻¹ after 6.5 s of hovering, (2) the mean RER during single hovering events was at its steady-state level of 1 only at oxygen uptake rates of 25–29 ml g⁻¹ h⁻¹, and (3) when the oxygen potentially released from estimated oxygen stores was added to the measured oxygen uptake, the upper limit for oxygen consumption during hovering was found to be 29 ml O₂ g⁻¹ h⁻¹. Hovering power input was about 1.2 times the value of minimum flight power input (Winter and von Helversen 1998) and thus well below the 1.7–2.6 difference in power output postulated by aerodynamic theory (Norberg et al. 1993). Mass specific power input was 40% less than in hummingbirds. Thus, within the possible modes of hovering flight, Glossophaga bats seem to operate at the high-efficiency end of the spectrum. Accepted: 28 April 1998     

Lhcb2 gene expression analysis in two ecotypes of Sedum alfredii subjected to Zn/Cd treatments with functional analysis of SaLhcb2 isolated from a Zn/Cd hyperaccumulator

The Lhcb2 gene from hyperaccumulator Sedum alfredii was up-regulated more than three-fold while the non-hyperaccumulator accumulated one or two-fold higher amount of the mRNA than control plants under different concentrations of Cd²⁺ for 24 h. Lhcb2 expression was up-regulated more than five-fold in a non-hyperaccumulator S. alfredii when exposed to 2 μM Cd²⁺ or 50 μM Zn²⁺ for 8 d and the hyperaccumulator had over two-fold more mRNA abundance than the control plants. Over-expression of SaLhcb2 increased the shoot biomass by 14–41% and the root biomass by 21–57% without Cd²⁺ treatment. Four transgenic tobacco lines (L5, L7, L10 and L11) possessed higher shoot biomass than WT plants with Cd²⁺. Four transgenic lines (L7, L8, L10 and L11) accumulated 6–35% higher Cd²⁺ amounts in shoots than the wild type plants.     

Assaying Total Carotenoids in Flours of Corn and Sweetpotato by Laser Photoacoustic Spectroscopy

This study describes the application of the laser photoacoustic spectroscopy (PAS) for quantification of total carotenoids (TC) in corn flours and sweetpotato flours. Overall, thirty-three different corn flours and nine sweetpotato flours were investigated. All PAS measurements were performed at room temperature using 488-nm argon laser radiation for excitation and mechanical modulation of 9 and 30 Hz. The measurements were repeated within a run and within several days or months. The UV–Vis spectrophotometry was used as the reference method. The concentration range that allows for the reliable analysis of TC spans a region from 1 to 40 mg kg⁻¹ for corn flours and from 9 to 40 mg kg⁻¹ for sweetpotato flours. In the case of sweetpotato flours, the quantification may extend even to 240 mg kg⁻¹ TC. The estimated detection limit values for TC in corn and sweetpotato flours were 0.1 and 0.3 mg kg⁻¹, respectively. The computed repeatability (n = 3–12) and intermediate precision (n = 6–28) RSD values at 9 and 30 Hz are comparable: 0.1–17.1% and 5.3–14.7% for corn flours as compared with 1.4–9.1% and 4.2–23.0% for sweetpotato flours. Our results show that PAS can be successfully used as a new analytical tool to simply and rapidly screen the flours for their nutritional potential based on the total carotenoid concentration.