Protein assembly and heat stability in developing thylakoid membranes during greening

The development of the thylakoid membrane was studied during illumination of dark-grown barley seedlings by using biochemical methods, and Fourier transform infrared and spin label electron paramagnetic resonance spectroscopic techniques. Correlated, gross changes in the secondary structure of membrane proteins, conformation, composition, and dynamics of lipid acyl chains, SDS/PAGE pattern, and thermally induced structural alterations show that greening is accompanied with the reorganization of membrane protein assemblies and the protein-lipid interface. Changes in overall membrane fluidity and noncovalent protein-lipid interactions are not monotonic, despite the monotonic accumulation of chlorophyll, LHCII [light-harvesting chlorophyll a/b-binding (polypeptides) associated with photosystem II] apoproteins, and 18:3 fatty acids that follow a similar time course with highest rates between 12-24 h of greening. The 18:3 fatty acid content increases 2.8-fold during greening. This appears to both compensate for lipid immobilization by membrane proteins and facilitate packing of larger protein assemblies. The increase in the amount of protein-solvating immobile lipids, which reaches a maximum at 12 h, is caused by 40% decrease in the membranous mean diameter of protein assemblies at constant protein/lipid mass ratio. Alterations in the SDS/PAGE pattern are most significant between 6-24 h. The size of membrane protein assemblies increases approximately 4.5-fold over the 12-48-h period, likely caused by the 2-fold gain in LHCII apoproteins. The thermal stability of thylakoid membrane proteins increases monotonically, as detected by an increasing temperature of partial protein unfolding during greening. Our data suggest that a structural coupling between major protein and lipid components develops during greening. This protein-lipid interaction is required for the development and protection of thylakoid membrane protein assemblies.     

Benign solitary solid cold thyroid nodules: US-guided interstitial laser photocoagulation--initial experience

PURPOSE: To evaluate the effects of ultrasonography (US)-guided interstitial laser photocoagulation (ILP) on the volume of benign solitary solid cold thyroid nodules and any nodule-related symptoms. MATERIALS AND METHODS: ILP was performed in 16 patients with normal thyroid function and a solid benign thyroid nodule. None of the patients had uptake on a radionuclide scan. Patients underwent one ILP session. A needle was positioned in the thyroid nodule with US guidance, and the laser fiber was placed in the lumen of the needle. Patients were treated for 287-1,200 seconds with an output power of 1-3 W. ILP was performed with continuous US guidance and terminated when the echogenic changes were stationary. Thyroid nodule volume and thyroid function were evaluated before and 1, 3, and 6 months after treatment. During the same period, 15 untreated patients (control group) were followed up to evaluate the size of the untreated thyroid nodule. RESULTS: In the 16 patients treated with ILP, the mean thyroid nodule volume decreased from 10 to 5.4 mL (P <.001) after 6 months. The median energy given was 761 J. There was no relationship between the dose of thermal energy given and nodule reduction. Pressure symptoms were significantly reduced (P =.0002) after 6 months. The treatment was well-tolerated in all patients. No significant change in thyroid nodule volume was seen in the control group. CONCLUSION: US-guided ILP could become a useful nonsurgical alternative in the treatment of the benign solitary solid cold thyroid nodule in patients who cannot or will not undergo surgery.     

Effect of ketamine on dendritic arbor development and survival of immature GABAergic neurons in vitro.

Ketamine, a noncompetitive antagonist of the N-methyl-D-aspartate type of glutamate receptors, was reported to induce neuronal cell death when administered to produce anesthesia in young rodents and monkeys. Subanesthetic doses of ketamine, as adjuvant to postoperative sedation and pain control, are also frequently administered to young children. However, the effects of these low concentrations of ketamine on neuronal development remain unknown. The present study was designed to evaluate the effects of increasing concentrations (0.01-40 microg/ml) and durations (1-96 h) of ketamine exposure on the differentiation and survival of immature gamma-aminobutyric acidergic (GABAergic) interneurons in culture. In line with previous studies (Scallet et al., 2004), we found that a 1-h-long exposure to ketamine at concentrations > or = 10 microg/ml was sufficient to trigger cell death. At lower concentrations of ketamine, cell loss was only observed when this drug was chronically (> 48 h) present in the culture medium. Most importantly, we found that a single episode of 4-h-long treatment with 5 microg/ml ketamine induced long-term alterations in dendritic growth, including a significant (p < 0.05) reduction in total dendritic length and in the number of branching points compared to control groups. Finally, long-term exposure (> 24 h) of neurons to ketamine at concentrations as low as 0.01 microg/ml also severely impaired dendritic arbor development. These results suggest that, in addition to its dose-dependent ability to induce cell death, even very low concentrations of ketamine could interfere with dendritic arbor development of immature GABAergic neurons and thus could potentially interfere with the development neural networks.     

The Duration of Measuring Partial AUCs for the Assessment of Bioequivalence

Purpose. To determine favourable sampling conditions for assessing bioequivalence by the comparison of partial AUCs in the early phase of concentration-time profiles. Methods. Two-period crossover trials were simulated. They assumed a wide range of the ratios of absorption rate constants of the test (T) and reference (R) formulations (k_aT/k_aR). Averages and standard deviations of the corresponding ratios of simulated partial AUCs (AUC_pT/AUC_pR) were determined together with the statistical power of assessing bioequivalence, i.e., the percentage of simulated trials in which bioequivalence was declared. Results. The power for stating bioequivalence was high when AUC_P was recorded until the earlier rather than the later of two peaks in each subject. Similarly, power was comparatively high when AUC_P was measured until the time of the reference peak instead of multiples of this time. Power was high also when AUC_p was determined until the fixed true, population mean time of the reference formulation instead of multiples of this time. The pattern for the kinetic sensitivity parallelled that found for the power, while the standard deviations changed generally in the opposite direction. Conclusions. The effectiveness (power) of evaluating bioequivalence in the early phase of concentration-time profiles by partial AUCs generally decreases when the duration for measuring the metric is extended. Among the investigated designs, determination of partial AUCs until the earlier of two peaks in each subject is the most powerful.     

Metrics Comparing Simulated Early Concentration Profiles for the Determination of Bioequivalence

Purpose. To compare the effectiveness of various metrics which evaluate bioequivalence in the early phase of concentration-time profiles. Methods. Two-period crossover trials were simulated with increasing assumed ratios of the true absorption rate constants of the two formulations, and with various kinetic models. Kinetic sensitivities (KS) and standard errors (SE) of the various metrics were recorded and the percentage of trials accepting bioequivalence (the statistical power) was evaluated. The principal metrics included the partial AUC (AUC _P) the intercept obtained by linear extrapolation of the ratios of the lower over higher concentrations (C) measured for the two formulations (I _{L /H}), and the ratios of intercepts extrapolated from logarithmic C/ time values of the two products (M _log). For comparison, also properties of C _maxand an ideally evaluated measure (Id) were determined. Results. M _logshowed generally the highest statistical power and KS, and also the largest SE, closely followed by I _{L /H}. Partial AUC exhibited lower power and KS, but also smaller SE than the intercept procedures. The three methods had much higher power, KS and SE than C _max. These comparisons were maintained over various kinetic conditions and experimental designs. The effective evaluation of bioequivalence in the early phase of studies is assured with 3 (or more) measurements until the population average peak of the reference formulation. Conclusions. The three principal methods assess bioequivalence very effectively in the early phase of a concentration-time profile. M _loghad the highest statistical power, closely followed by I_{L /H}and then by partial AUC.     

Lorazepam in cancer patients treated with cisplatin: a drug having antiemetic, amnesic, and anxiolytic effects

There currently is no pharmacologic approach to the problem of anticipatory nausea and vomiting (ANV). Lorazepam (Ativan, Wyeth Laboratories, Philadelphia) is an interesting candidate drug if it could block the recall of the unpleasant events associated with chemotherapy, especially if it also has antiemetic properties. Since ANV is a conditioned (learned) response, it may well depend on a memory imprint of the stimulus. This pilot study was designed to use intravenous lorazepam given before and after cisplatin infusion in 32 patients, and to make detailed measurements of nausea, vomiting, recent memory, anxiety, and sedation as well as toxicity. Satisfactory responses occurred in about 70%, as rated separately both by investigator and patient. Forty-six percent did not even recall receiving chemotherapy, regardless of whether or not they vomited; 80% had no significant anxiety after chemotherapy. Adverse reactions included some cases of perceptual disturbance, urinary incontinence, diarrhea, hypotension, and one case of severe transient amnesia. No long-term adverse effects were noted.