LETd Optimization Verification With an SOI Microdosimeter

PURPOSE

A first of its kind experimental verification of dose-averaged linear energy transfer (LETd) optimized treatment plans for proton therapy has been carried out using a silicon-on-insulator microdosimeter at the Massachusetts General Hospital (MGH), Boston, USA.

METHODS AND MATERIALS

Three clinical treatment plans of a typical ependymoma structure set were designed using the standard clinical approach, the proposed protocol approach, and a one-field approach. The plans were then reoptimized to reduce the LETd-weighted dose in the brain stem. All six plans were delivered in a solid water phantom and the experimental yD‾ measured.

RESULTS

After LETd optimization, a reduction in yD‾ was found within the brain stem by an average of 12%, 19%, and 4% for the clinical, protocol, and one-field plans, respectively, while maintaining adequate coverage of the tumor structure. The experimental LETd-weighted doses were in agreement with the treatment planning system calculations and Monte Carlo simulations and reinforced the improvement of the optimization.

CONCLUSIONS

This work demonstrates the first experimental verification of the clinical implementation of LETd optimization for patient treatment with proton therapy.

A glassy carbon electrode modified with polyaniline nanowires: An electrochemically effective surface area and an electrocatalytic activity for the oxidation of methanol under alkaline conditions

Polyaniline nanowires are directly synthesized on a glassy carbon electrode (3 mm diameter) by an electrochemical process. The polyaniline nanowires, of uniform size, a diameter of 85–95 nm, and high conductivity, distribute evenly throughout the surface of the working electrode. Electrochemical measurements are conducted in order to determine the electrochemically effective surface area of the obtained glassy carbon electrode modified with polyaniline nanowires, and an investigation of the electrocatalytic activity of polyaniline nanowires for the oxidation of methanol under alkaline conditions is carried out. The electrochemically effective surface area of the glassy carbon electrode modified with polyaniline nanowires is nearly 27 times larger than that of a glassy carbon electrode. In a cyclic voltammetry curve of the glassy carbon electrode modified with polyaniline nanowires measured in a 3.0 M CH3OH and 0.5 M KOH solution, an anodic peak corresponding to the oxidation of methanol under alkaline conditions appears at 0.17 V with a peak current of 34.4 μA.

Effects of pretreatment and air drying temperature on Noni fruit powder

The plant Morinda citrifolia L. (Noni) has been the subject of several recent research due to its positive impact on the treatment and prevention of a variety of diseases. Noni fruits contain a variety of phytochemicals, including flavonoid, polyphenol, and triterpenoid saponin. This study aimed to determine the best pre-treatment (including blanching, soaking in ascorbic acid solution and metabisulfite solution) and air-drying temperature (50, 60, 70, and 80 °C) to maximize the total polyphenol content (TPC), flavonoid content (TFC), and triterpenoid saponin contents (TSC) of the resultant Noni fruit powder. The results revealed that pre-soaked Noni fruit samples in ascorbic acid or metabisulfite solution before air-drying at 60 °C were beneficial in preserving TPC, TFC, and TSC. TPC, TFC, and TSC losses increased as drying temperatures (70 and 80 °C) rose. The optimum sample was held at five different relative humidity conditions until they attained weight equilibrium. The results indicated that the sorption isotherm curve of the Noni powder was the sigmoid shape and fitted with the BET and GAB models.

Electrosynthesis of electrochemically reduced graphene oxide/polyaniline nanowire/silver nanoflower nanocomposite for development of a highly sensitive electrochemical DNA sensor

A novel nanostructured electrode material based on electrochemically reduced graphene oxide/polyaniline nanowires/silver nanoflowers (ERGO/PANi NWs/AgNFs) was fabricated site-specifically onto a Pt microelectrode (0.80 mm² area) using a three-step electrochemical procedure: electrosynthesis of ERGO, electropolymerization of PANi NWs, and electrodeposition of AgNFs. Synergistic and complementary properties of ERGO, PANi NWs and AgNFs, including high electrochemical activity, large surface area, and high biocompatibility, were obtained. Besides, the electrosynthesis method allowed the direct formation of the desired nanomaterial onto the Pt microelectrode, so the adhesion between the sandwich-structured nanocomposite and the electrode surface was also improved. The optimized ERGO/PANi NWs/AgNFs nanocomposite was used for the first time to develop an electrochemical DNA sensor. As a result, the DNA probe immobilization was facilitated and the electrochemical signals of the DNA sensor were enhanced. The detection limit of the DNA sensor was 2.70 × 10⁻¹⁵ M. Moreover, potential miniaturization for fabrication of a lab-on-a-chip system, direct detection, high sensitivity, and good specificity are the advantages of the fabricated DNA sensor.

A novel nanostructured material based on ERGO/PANi NWs/AgNFs was electrosynthesized on a Pt microelectrode and was used for the first time to develop an electrochemical DNA sensor.

Graphene Oxide/Polyvinyl Alcohol/Fe3O4 Nanocomposite: An Efficient Adsorbent for Co(II) Ion Removal

In this work, an effective nanocomposite-based adsorbent directed to adsorb cobalt (Co²⁺) ion was successfully synthesized from graphene oxide (GO), polyvinyl alcohol (PVA), and magnetite (Fe₃O₄) nanoparticles via a coprecipitation technique. The synthesized GO/PVA/Fe₃O₄ nanocomposite was applied for Co²⁺ ion removal with the optimized working conditions including 100 min of contact time, 0.01 g of adsorbent dosage, pH of 5.2, and 50°C of temperature. The investigation of adsorption kinetics showed that the adsorption of Co²⁺ ion onto the GO/PVA/Fe₃O₄ nanocomposite followed the pseudo-second-order kinetic model with the rate constant k₂ being 0.0026 (g mg^-1·min^-1). The Langmuir model is suitable to describe the adsorption of Co²⁺ ion onto the GO/PVA/Fe₃O₄ nanocomposite with the maximum sorption capacity (q _max) reaching 373.37 mg·g^-1. The obtained results also indicated that the GO/PVA/Fe₃O₄ nanocomposite can adsorb/regenerate for at least 5 cycles with a little reduction in removal efficiency. Therefore, we believe that the GO/PVA/Fe₃O₄ nanocomposite could be used as a potential adsorbent for heavy metal treatment in terms of high adsorption capacity, fast adsorption rate, and recyclability.

Modular gene analysis reveals distinct molecular signatures for subsets of patients with cutaneous lupus erythematosus

BACKGROUND

Cutaneous lupus erythematosus (CLE) is a heterogeneous autoimmune disease with clinical sequelae such as itching, dyspigmentation and scarring.

OBJECTIVES

We applied a previously described modular analysis approach to assess the molecular heterogeneity of patients with CLE.

METHODS

Whole-blood transcriptomes of RNA sequencing data from a racially and ethnically diverse group of patients with CLE (n = 62) were used to calculate gene co-expression module scores. An unsupervised cluster analysis and k-means clustering based on these module scores were then performed. We used Fisher's exact tests and Kruskal-Wallis tests to compare characteristics between patient clusters.

RESULTS

Six unique clusters of patients with CLE were identified from the cluster analysis. We observed that seven inflammation modules were elevated in two clusters of patients with CLE. Additionally, these clusters were characterized by interferon, neutrophil and cell-death signatures, suggesting that interferon-related proteins, neutrophils and cell-death processes could be driving the inflammatory response in these subgroups. Three different clusters had a predominant T-cell signature, which were supported by lymphocyte counts.

CONCLUSIONS

Our data support a diverse molecular profile in CLE that further adds to the clinical variations of this skin disease, and may affect disease course and treatment selection. Future studies with a larger and diverse cohort of patients with CLE are warranted to confirm these findings.

Stress in Parents of Children With Genetically Determined Leukoencephalopathies: A Pilot Study

Genetically determined leukoencephalopathies comprise a group of rare inherited white matter disorders. The majority are progressive diseases resulting in early death. We performed a cross-sectional pilot study including 55 parents from 36 families to assess the level of stress experienced by parents of patients with genetically determined leukoencephalopathies, aged 1 month to 12 years. Thirty-four mothers and 21 fathers completed the Parenting Stress Index-4th Edition. One demographic questionnaire was completed per family. Detailed clinical data was gathered on all patients. Statistical analysis was performed with total stress percentile score as the primary outcome. Mothers and fathers had significantly higher stress levels compared with the normative sample; 20% of parents had high levels of stress whereas 11% had clinically significant levels of stress. Mothers and fathers had comparable total stress percentile scores. We identified pediatric behavioral difficulties and gross motor function to be factors influencing stress in mothers. Our study is the first to examine parental stress in this population and highlights the need for parental support early in the disease course. In this pilot study, we demonstrated that using the Parenting Stress Index-4th Edition to assess stress levels in parents of patients with genetically determined leukoencephalopathies is feasible, leads to valuable and actionable results, and should be used in larger, prospective studies.

The impact of sensitive volume thickness for silicon on insulator microdosimeters in hadron therapy

Compact silicon on insulator (SOI) microdosimeters have been used to characterise the radiation field of many different hadron therapy beams. SOI devices are particularly attractive in hadron therapy fields due to their spatial resolution being well suited to the sharp dose gradients at the end of the primary beam's range. Due to the small size of SOI's sensitive volumes (SVs), which are usually  ∼1-10 [Formula: see text]m thick, the fabrication of these devices can present challenges which are not as common for more conventional thickness silicon devices such as silicon spectroscopy detectors. Microdosimetry is the study of the energy deposition in micrometre sized volumes representing biological sites and is a powerful approach to estimate the biological effect of radiation on the micron-scale level, in a cell. However, cell sizes vary extensively translating in different energy deposition spectra. This work studies SV thicknesses between 1 and 100 [Formula: see text]m using Geant4 and examines the impact of SV dimensions on microdosimetric quantities. The quantities studied were the frequency mean lineal energy, [Formula: see text], and the dose mean lineal energy, [Formula: see text]. Additionally the relative biological effectiveness (RBE), estimated by the microdosimetric kinetic model (MKM), is also investigated. To study the impact of the SV thickness, SOI microdosimeters were irradiated with proton, [Formula: see text] and [Formula: see text] ion beams with ranges of  ∼160 mm, with the microdosimeter being set at various positions along the Bragg curve. It was found that [Formula: see text] was influenced the least in proton beams and increased for heavier ion beams. Conversely, [Formula: see text] was impacted by the SV thickness the most in proton beams and [Formula: see text] was the least. Similar to [Formula: see text], protons were impacted the most by the SV thickness when estimating the RBE using the MKM. The cause of these differences was largely due to the different densities of the delta electron track structure for the case of [Formula: see text] and the energy transferred to the medium from the primary beam for [Formula: see text].

Optimisation of the design of SOI microdosimeters for hadron therapy quality assurance

Silicon-on-insulator (SOI) microdosimeters offer a promising method for routine quality assurance (QA) for hadron therapy due to their ease of operation and high spatial resolution. However, one complication which has been shown previously is that the traditional use of the mean chord length, [Formula: see text], calculated using Cauchy's formula, for SOI devices in clinical carbon ion fields is not appropriate due to the strong directionality of the radiation field. In a previous study, we demonstrated that the mean path length, [Formula: see text], which is the mean path of charged particles in the sensitive volume (SV), is a more appropriate method to obtain microdosimetric quantities and biological relevant values, namely the relative biological effectiveness (RBE) by means of the microdosimetric kinetic model. The previous work, which was limited to mono-energetic [Formula: see text] ion beams typical of heavy ion therapy (HIT), is extended here to investigate the [Formula: see text] in a pristine proton beam as well as for spread out Bragg peaks (SOBP) for both proton and carbon ion clinical beams. In addition, the angular dependence of the SOI device for a number of different SV designs is also investigated to quantify the effects which the alignment has on the [Formula: see text]. It is demonstrated that the [Formula: see text] can be accurately estimated along the depth of a pristine or SOBP using the energy deposition spectra for both proton and [Formula: see text] ion beams. This observation allows a quick and accurate estimation of the [Formula: see text] for experimental use.

MICRODOSIMETRIC APPLICATIONS IN PROTON AND HEAVY ION THERAPY USING SILICON MICRODOSIMETERS

Using the CMRP 'bridge' μ+ probe, microdosimetric measurements were undertaken out-of-field using a therapeutic scanning proton pencil beam and in-field using a 12C ion therapy field. These measurements were undertaken at Mayo Clinic, Rochester, USA and at HIMAC, Chiba, Japan, respectively. For a typical proton field used in the treatment of deep-seated tumors, we observed dose-equivalent values ranging from 0.62 to 0.99 mSv/Gy at locations downstream of the distal edge. Lateral measurements at depths close to the entrance and along the SOBP plateau were found to reach maximum values of 3.1 mSv/Gy and 5.3 mSv/Gy at 10 mm from the field edge, respectively, and decreased to ~0.04 mSv/Gy 120 mm from the field edge. The ability to measure the dose-equivalent with high spatial resolution is particularly relevant to healthy tissue dose calculations in hadron therapy treatments. We have also shown qualitatively and quantitively the effects critical organ motion would have in treatment using microdosimetric spectra. Large differences in spectra and RBE10 were observed for treatments where miscalculations of 12C ion range would result in critical structures being irradiated, showing the importance of motion management.

Estimating development rate and thermal requirements of Bactericera cockerelli (Hemiptera: Triozidae) reared on potato and tomato by using linear and nonlinear models

The temperature-dependent development of tomato psyllid (also called potato psyllid), Bactericera cockerelli (Sulc), was studied in the laboratory at seven constant temperatures (8, 10, 15, 20, 23, 27, and 31°C), 50-60% RH, and a photoperiod of 16:8 (L:D) h on leaves of whole potato (Solanum tuberosum L.) and tomato (Solanum lycopersicum L.) plants. Developmental time in days for immature stages and total development (egg to adult) on both host species were inversely proportional to temperature between 8 and 27°C but increased at 31°C. One linear and two nonlinear models were fitted to the data. The lower developmental thresholds, calculated using the linear model for egg, total nymph, and total development (from oviposition to adult emergence) were 7.9, 4.2, and 7.1°C (reared on potato) and 7.2, 5.3, and 7.5°C (reared on tomato), respectively. The thermal constant (K) for total development was 358 (reared on potato), and 368 (reared on tomato) degree-days (DD). Two nonlinear models, Briere and Lactin, fit the data well as measured by goodness-of-fit criteria, the residual sum of square (RSS) and Akaike information criterion (AIC). Temperature threshold parameters for these nonlinear models (T(0), T(opt), and T(max)) were estimated for eggs, total nymphal stages, and total development time (egg to adult). The Briere model is highly recommended for the description of temperature-dependent development of tomato psyllid. Results from this study will provide basic information on the biology of tomato psyllid and have potential for the development of predictive models of the seasonal progress of this invasive pest.

Endothelin-1 modulates angiotensin II in the development of hypertension in fructose-fed rats

Two of the most potent vasoconstrictors, endothelin-1 (ET-1) and angiotensin II (Ang II), are upregulated in fructose hypertensive rats. It is unknown whether an interrelationship exists between these peptides that may contribute to the development of fructose-induced hypertension. The objective of this study was to investigate the existence of an interaction between the endothelin and renin angiotensin systems that may play a role in the development of fructose-induced hypertension. High fructose feeding and treatment with either bosentan, a dual endothelin receptor antagonist, or with L-158,809, an angiotensin type 1 receptor antagonist, were initiated simultaneously in male Wistar rats. Systolic blood pressure, fasted plasma parameters, insulin sensitivity, plasma Ang II, and vascular ET-1-immunoreactivity were determined following 6 weeks of high fructose feeding. Rats fed with a high fructose diet exhibited insulin resistance, hyperinsulinemia, hypertriglyceridemia, hypertension, and elevated plasma Ang II. Treatment with either bosentan or L-158,809 significantly attenuated the rise in blood pressure with no effect on insulin levels or insulin sensitivity in fructose-fed rats. Bosentan treatment significantly reduced plasma Ang II levels, while L-158,809 treatment significantly increased vascular ET-1-immunoreactivity in fructose-fed rats. Thus, treatment with the endothelin receptor antagonist prevented the development of fructose-induced hypertension and decreased plasma Ang II levels. These data suggest that ET-1 contributes to the development of fructose-induced hypertension through modulation of Ang II levels.

Photoperiod, reproduction, and immunity in select strains of inbred mice

The purpose of this study was to determine whether decreased day lengths affect reproduction or the immune system in inbred mice. Irrespective of a nocturnal pineal melatonin rise, the signal for day length information, body and testis weights were the same in various strains 8 weeks after transfer from long to short days (16 to 8 h of light/day) compared to mice that remained in long days. Serum testosterone was unaffected by the photoperiod shift. The second goal was to determine whether the shift from long to short days influenced lymphocyte populations in spleen or blood, as well as innate and cell-mediated immune cell functions in C3H/HeN mice, an inbred strain with a robust melatonin rhythm. By flow cytometry, a stable percentage and number of B cells, T cells, and natural killer cells were identified in spleen from mice in both long and short days during the day and night. This complement of immunophenotypes in spleen suggests that equivalent functional capabilities persist in secondary lymphoid tissue of mice irrespective of day length. This was supported by findings that cytolytic activity by splenic natural killer cells (innate immunity) and antigen-induced T cell-dependent B cell antibody production (adaptive immunity) were similar in mice in long and short days. In blood, cell numbers but not helper T cell subset percentages (i.e., naive, memory, cytotoxic, or activated) were augmented in mice in short compared to long days, a consequence of increased circulating B cells. Day length differences in certain immunophenotypes in circulation may forecast photoperiod-mediated alterations in responsiveness to pathogens that are associated with a change in season. At night, the reduced proportion of cytotoxic T cells (long and short days), as well as increases in the percentage of activated T cells (long days), B cells (short days), and NK cell activity (long and short days) relative to daytime, suggests that surveillance and function by select immunophenotypes may adapt to circadian transitions even in highly inbred species. Thus, inbred mice retain capabilities for photoperiod to influence trait-specific aspects of immune cell but not reproductive function.

P-113D, an antimicrobial peptide active against Pseudomonas aeruginosa, retains activity in the presence of sputum from cystic fibrosis patients

Antimicrobial peptides are a source of novel agents that could be useful for treatment of the chronic lung infections that afflict cystic fibrosis (CF) patients. Efficacy depends on antimicrobial activity against the major pathogens of CF patients, Pseudomonas aeruginosa, Staphylococcus aureus, and Haemophilus influenzae, in the environment of the CF patient's airway. We describe the in vitro efficacies of derivatives of histatins, which are histidine-rich peptides produced by the salivary glands of humans and higher primates. P-113, a peptide containing 12 of the 24 amino acid residues of the parent molecule, histatin 5, retained full antibacterial activity and had a good spectrum of activity in vitro against the prominent pathogens of CF patients. However, P-113 was not active in the presence of purulent sputum from CF patients. In contrast, P-113D, the mirror-image peptide with the amino acid residues in the D configuration, was stable in sputum, was as active as P-113 against pathogens of CF patients in the absence of sputum and retained significant activity in the presence of sputum from CF patients. Recombinant human DNase, which effectively liquefies sputum, enhanced the activity of P-113D in undiluted sputum against both exogenous (added) bacteria and endogenous bacteria. Because of its properties, P-113D shows potential as an inhalant in chronic suppressive therapy for CF patients.

Photoperiod modulates the inhibitory effect of in vitro melatonin on lymphocyte proliferation in female Siberian hamsters

In Siberian hamsters (Phodopus sungorus), short days suppress reproductive function and lymphocyte proliferation. To determine whether melatonin influences cell-mediated immunity through a direct action on lymphocyte proliferation, in vitro responsiveness to mitogens and melatonin was assessed in systemic and splenic lymphocytes from adult female Siberian hamsters housed in either long or short days for 13 weeks. Short days provoked reproductive regression and reduced lymphocyte proliferation. Physiological concentrations of melatonin (50 pg/ml) inhibited in vitro proliferation of circulating lymphocytes, whereas higher concentrations (> or = 500 pg/ml) were required to inhibit proliferation of splenic lymphocytes. Immunomodulatory effects of melatonin were restricted to lymphocytes from long-day hamsters-in vitro melatonin had no effect on circulating or splenic lymphocytes from females in short days. Responsiveness to melatonin in short-day lymphocytes may be restrained by the already expanded nightly pattern of melatonin secretion in short days. These data support the hypothesis that melatonin acts directly on lymphocytes from long-day hamsters to suppress blastogenesis.

Anticandida activity is retained in P-113, a 12-amino-acid fragment of histatin 5

Through the analysis of a series of 25 peptides composed of various portions of the histatin 5 sequence, we have identified P-113, a 12-amino-acid fragment of histatin 5, as the smallest fragment that retains anticandidal activity comparable to that of the parent compound. Amidation of the P-113 C terminus increased the anticandidal activity of P-113 approximately twofold. The three histidine residues could be exchanged for three hydrophobic residues, with the fragment retaining anticandidal activity. However, the change of two or more of the five basic (lysine and arginine) residues to uncharged residues resulted in a substantial loss of anticandidal activity. A synthetic D-amino-acid analogue, P-113D, was as active against Candida albicans as the L-amino-acid form. In vitro MIC tests in low-ionic-strength medium showed that P-113 has potent activity against Candida albicans, Candida glabrata, Candida parapsilosis, and Candida tropicalis. These results identify P-113 as a potential antimicrobial agent in the treatment of oral candidiasis.

Selection of a Bifidobacterium strain to complement resistant starch in a synbiotic yoghurt

AIMS

To employ an in vitro screening regime to select a probiotic Bifidobacterium strain to complement resistant starch (Hi-maizetrade mark) in a synbiotic yoghurt.

METHODS AND RESULTS

Of 40 Bifidobacterium isolates examined, only B. lactis Laftitrade mark B94 possessed all of the required characteristics. This isolate hydrolysed Hi-maizetrade mark, survived well in conditions simulating passage through the gastrointestinal tract and possessed technological properties suitable for yoghurt manufacture. It grew well at temperatures up to 45 degrees C, and grew to a high cell yield in an industrial growth medium. In addition to resistant starch, the organism was able to utilize a range of prebiotics including inulin, and fructo-, galacto-, soybean- and xylo-oligosaccharides. Pulse field gel electrophoresis of restriction enzyme cut chromosomal DNA revealed that B. lactis Laftitrade mark B94 was very closely related to the B. lactis Type Strain (DSM 10140), and to the commercial strains B. lactis Bb-12 and B. lactis DS 920. However, B. lactis Laftitrade mark B94 was the only one of these isolates that could hydrolyse Hi-maizetrade mark. This phenotypic difference did not appear to be due to the presence of plasmid encoded amylase. Bifidobacterium lactis Laftitrade mark B94 survived without substantial loss of viability in synbiotic yoghurt containing Hi-maizetrade mark during storage at 4 degrees C for six weeks.

CONCLUSION

Bifidobacterium lactis Laftitrade mark B94 is a promising new yoghurt culture that warrants further investigation to assess its probiotic potential.

SIGNIFICANCE AND IMPACT OF THE STUDY

In vitro screening procedures can be used to integrate complementary probiotic and prebiotic ingredients for new synbiotic functional food products.

A logistic regression of risk factors for disease occurrence on Asian shrimp farms

Serious shrimp-disease outbreaks have reduced shrimp production and slowed industry growth since 1991. This paper tests factors such as farm sitting and design, and farm-management practices for relationships with disease occurrence. Logistic regression is used to analyze farm-level data from 3951 shrimp farms in 13 Asian countries. Disease occurrence is modeled as a 0-1 variable where 1 = disease loss of > or = 20% to any 1 crop, and 0 = losses of < 20%. Logistic regression is performed for each of 3 levels of shrimp culture intensity, i.e. extensive, semi-intensive, and intensive. Attempts to apply logistic regression models to each country were not successful due to insufficient data for most countries. Factors affecting disease occurrences were quite different for different farming intensities. Farms that had larger pond production areas, with larger number of farms discharging effluent into their water supply canals, and removed silt had greater disease occurrence. On the other hand, farms that practiced polyculture and took water from the sea through a canal had lower disease occurrence.

Epidemiological study of Candida spp. colonization in cardiovascular surgical patients

Candida infections involve multiple risk factors. Among the independent risk factors identified, the degree of colonization of Candida spp. allows the prediction of subsequent severe candidosis in surgical patients. The aim of this study was to assess among 13 selected variables, those that would best predict the perioperative variation of the colonization index (CI) of Candida spp. in cardiovascular surgical patients. The colonization index took into account the number of sites colonized and the density of growth. The results showed that 56.8% of our patients were colonized perioperatively. A total of 116 isolates were identified and Candida albicans accounted for 76.7% of the strains. Among the patients who developed post-surgical Candida infections, 57.1% had an increase of the CI early after the operation. By univariate analysis, three factors were significantly associated with an increase of the CI in patients after surgery; sex (female), the duration of central intravascular catheterization and the length of stay in the surgical intensive care unit (SICU). Epidemiological data could help predict those patients who are at risk of developing Candida infections.

Grapefruit juice-terfenadine single-dose interaction: magnitude, mechanism, and relevance

OBJECTIVE

To investigate the single dose-response effects of grapefruit juice on terfenadine disposition and electrocardiographic measurements.

METHODS

Twelve healthy males received 250 ml water or regular- or double-strength grapefruit juice with 60 mg terfenadine in a randomized crossover trial. Plasma concentrations of the cardiotoxic agent terfenadine and the active antihistaminic metabolite terfenadine carboxylate were determined over 8 hours. The QTc interval was monitored.

RESULTS

Terfenadine concentrations were measurable (> 1 ng/ml) in 27 (20%; p < 0.001) and 39 (30%; p < 0.001) samples from individuals treated with regular- and double-strength grapefruit juice, respectively, compared to only four (3%) samples with water. Terfenadine plasma peak drug concentration (Cmax) was also higher. Terfenadine carboxylate area under the plasma drug concentration-time curve (AUC), Cmax, and time to reach Cmax (tmax) were increased by both strengths of juice. However, terfenadine carboxylate apparent elimination half-life (t1/2) was not altered. The magnitude of the interaction of terfenadine carboxylate AUC and Cmax ranged severalfold and correlated among individuals for regular-strength (r2 = 0.87; p < 0.0001) and double-strength (r2 = 0.78; p < 0.0001) grapefruit juice. No differences in the pharmacokinetics of terfenadine and terfenadine carboxylate were observed between the two strengths of grapefruit juice. QTc interval was not altered.

CONCLUSIONS

A normal amount of regular-strength grapefruit juice produced maximum single-dose effects on terfenadine and carboxylic acid metabolite pharmacokinetics. The mechanism likely involved reduced presystemic drug elimination by inhibition of more than one metabolic pathway. The extent of the interaction was not sufficient to produce electrocardiographic changes. However, the pharmacokinetic effects were highly variable among individuals. This study further enhances the awareness of the potential for a serious interaction between grapefruit juice and terfenadine.

Erythromycin-felodipine interaction: magnitude, mechanism, and comparison with grapefruit juice

OBJECTIVE

To investigate a potentially marked effect by erythromycin on felodipine pharmacokinetics, to characterize the mechanism, and to compare the interaction with that between grapefruit juice and felodipine.

METHODS

Felodipine, 10 mg extended release, was administered with 250 ml water, 250 mg erythromycin, or 250 ml grapefruit juice in a randomized crossover study of 12 healthy men. Erythromycin base, 250 mg four times a day, was started the day before and continued on that study day. Pharmacokinetic values of felodipine, the primary metabolite dehydrofelodipine, and the major secondary derivative M3 metabolite were studied.

RESULTS

Compared with water, erythromycin produced severalfold higher felodipine area under the plasma drug concentration-time profile (AUC), plasma peak drug concentration (Cmax), and apparent elimination half-life (t1/2); however, the effect was variable among individuals. Erythromycin augmented dehydrofelodipine AUC, Cmax, and t1/2 but decreased dehydrofelodipine/felodipine ratios. The AUC of the M3 metabolite and the M3 metabolite/dehydrofelodipine ratios were reduced. These findings support inhibition of both metabolic pathways likely mediated by CYP3A4. Grapefruit juice produced similar mean effects but did not prolong felodipine or dehydrofelodipine t1/2. Individually, felodipine AUC with erythromycin was greater than or similar to that with grapefruit juice. Relative felodipine AUC (erythromycin compared with grapefruit juice) correlated with relative felodipine Cmax but not with relative felodipine t1/2, suggesting felodipine AUC differed between these treatments, mainly from factors affecting presystemic drug elimination.

CONCLUSIONS

Erythromycin produced an important pharmacokinetic interaction with felodipine by inhibition of drug metabolism. Although erythromycin and grapefruit juice shared a common mechanism, erythromycin likely reduced felodipine biotransformation at the gut wall and liver, whereas single-dose grapefruit juice had an effect mainly at the gut wall.

Oxidative stress response in yeast: glutathione peroxidase of Hansenula mrakii is bound to the membrane of both mitochondria and cytoplasm

The yeast Hansenula mrakii IFO 0895 induces glutathione peroxidase (GPx) when the cells are exposed to the oxidative stress such as lipid hydroperoxide, superoxide- and hydroxy radical-generating conditions. To clarify the localization of GPx in H. mrakii cell, distribution of the enzyme was investigated. After centrifugation of the yeast protoplast homogenates at 2500 x g for 10 min, 67% of total GPx activity was recovered from the supernatant (Sup. 1) and 33% was from the pellet (Pellet 1). When the Sup. 1 was fractionated by sucrose density gradient ultracentrifugation, GPx activity was essentially recovered from the mitochondria fraction. Submitochondrial localization of the enzyme showed that 95% and 2.5% of the enzyme was recovered from the inner and outer membrane, respectively. No GPx activity was detected neither in intermembrane space nor in matrix of mitochondria. On the other hand, at least 12% of total GPx activity was recovered from the purified plasma membrane which was obtained from the Pellet 1 by successive sucrose density gradient centrifugation. Thus, the GPx of H. mrakii is present in the inner and outer membrane of mitochondria as well as the plasma membrane.

Cytoskeletal regulation of Caco-2 intestinal monolayer paracellular permeability

An abnormal increase in intestinal paracellular permeability may be an important pathogenic factor in various intestinal diseases. The intracellular factors and processes that regulate and cause alteration of intestinal paracellular permeability are not well understood. The purpose of this study was to examine some of the intracellular processes involved in cytoskeletal regulation of intestinal epithelial paracellular permeability using the filter-grown Caco-2 intestinal epithelial monolayers. Cytochalasin-b and colchicine were used to disrupt the cytoskeletal elements, actin microfilaments, and microtubules. Cytochalasin-b (5 micrograms/ml) and colchicine (2 x 10(-5) M) at the doses used caused marked depolymerization and disruption of actin microfilaments and microtubules, respectively. Cytochalasin-b-induced disruption of actin microfilaments resulted in perturbation of tight junctions and desmosomes and an increase in Caco-2 monolayer paracellular permeability. The cytochalasin-b-induced disruption of actin microfilaments and subsequent changes in intercellular junctional complexes and paracellular permeability were not affected by inhibitors of protein synthesis (actinomycin-D or cycloheximide) or microtubule function (colchicine), but were inhibited by metabolic energy inhibitors (2,4-dinitrophenol or sodium azide). The cytochalasin-b-induced disturbance in Caco-2 actin microfilaments and intercellular junctional complexes and increase in paracellular permeability were rapidly reversed. The paracellular pathway "re-tightening" following cytochalasin-b removal was not affected by actinomycin-D, cycloheximide, or colchicine, but was inhibited by 2,4-dinitrophenol and sodium azide. The colchicine-induced disruption of microtubules did not have significant effect on actin microfilaments, intercellular junctions, or paracellular permeability. These findings suggest that cytochalasin-b-induced increase in Caco-2 monolayer paracellular permeability was due to actin microfilament mediated perturbation of intercellular junctional complexes. The re-tightening of paracellular pathways (following removal of cytochalasin-b) resulted from energy-mediated re-assembly of pre-existing actin microfilaments and intercellular junctional complexes. This re-closure process did not require protein synthesis or microtubule-mediated shuttling process.

Grapefruit juice-felodipine interaction: reproducibility and characterization with the extended release drug formulation

1. Felodipine 10 mg extended release was administered with 250 ml regular-strength grapefruit juice or water in a randomized crossover manner followed by a second grapefruit juice treatment in 12 healthy men. The pharmacokinetics of felodipine and primary oxidative metabolite, dehydrofelodipine, were evaluated. 2. Initial grapefruit juice treatment increased felodipine AUC (mean +/- s.d.; 56.6 +/- 21.9 vs 28.1 +/- 11.5 ng ml-1 h; P < 0.001) and Cmax (8.1 +/- 2.5 vs 3.3 +/- 1.2 ng ml-1; P < 0.001) compared with water. Felodipine tmax (median; 2.8 vs 3.0 h) and t1/2 (7.3 +/- 3.7 vs 6.9 +/- 3.6 h) were not altered. 3. Readministration of felodipine with grapefruit juice produced mean felodipine AUC (61.5 +/- 32.2 ng ml-1 h) and Cmax (8.4 +/- 4.8 ng ml-1) which were similar to the initial grapefruit juice treatment 1-3 weeks previously. Felodipine AUC (r = 0.73, P < 0.01) and Cmax (r = 0.69, P < 0.02) correlated between grapefruit juice treatments among individuals. 4. The % increase in felodipine AUC with the initial grapefruit juice treatment compared with water correlated with the % increase in felodipine Cmax among individuals (r = 0.80, P < 0.01). Dehydrofelodipine AUC (74.7 +/- 28.7 vs 48.5 +/- 16.3 ng ml-1 h; P < 0.01) and Cmax (12.1 +/- 2.9 vs 7.9 +/- 2.6 ng ml-1; P < 0.01) were augmented with grapefruit juice compared with water.(ABSTRACT TRUNCATED AT 250 WORDS)

The acetylcholinesterase oxime reactivator HI-6 in man: pharmacokinetics and tolerability in combination with atropine

In a double-blind, placebo-controlled, single-dose ascending pharmacokinetics and tolerance study, we evaluated the bispyridinium oxime HI-6 dichloride monohydrate (62.5, 125, 250, and 500 mg), administered intramuscularly with atropine sulphate, 2 mg, in 24 healthy male volunteers. The plasma HI-6 peak concentration (Cmax) and area under the concentration-time curve (AUC) demonstrated linear pharmacokinetics with low intradose variability, suggestive of uniformity of effect among subjects. HI-6 (500 mg) attained plasma drug concentrations that appeared adequate for practical use as an antidote. The mean +/- SD time to maximum plasma HI-6 concentration (tmax = 0.69 +/- 0.21 h, n = 16), and absorption half-life (t/2a = 0.17 +/- 0.05 h) indicated rapid onset of effect. The volume of distribution (Vd = 0.25 +/- 0.04 L kg-1 TBW) approximated the extracellular fluid volume. A high total body clearance (CL = 252 +/- 52 mL min-1) and short apparent elimination half-life (t/2e = 1.15 +/- 0.19 h) were expected for this polar quaternary ammonium drug. The renal clearance CLr = 137 +/- 33 mL min-1), which approximated the expected glomerular filtration rate, and 24 h urinary excretion of unchanged drug (55 +/- 10%) indicated substantial non-renal elimination. Blood pressure, heart rate, respiratory rate, electrocardiographic parameters, mental acuity, and vision were not altered. Adverse events and changes in serum, urine, and semen laboratory tests were mild. The pharmacokinetics, safety, and apparent efficacy of HI-6 suggest it may be a superior oxime antidote against nerve agent poisoning.

Oxidative stress response in yeast: purification and some properties of a membrane-bound glutathione peroxidase from Hansenula mrakii

Glutathione peroxidase was purified from the total membrane fractions of a yeast, Hansenula mrakii IFO 0895. The purified enzyme gave a single protein band with a molecular mass of 28 kDa on SDS-PAGE. The enzyme showed activity to various lipid hydroperoxides and their methyl esters. The enzyme was also active toward phosphatidylcholine hydroperoxide and cholesterol hydroperoxide. Since the enzyme was not active on hydrogen peroxide, the enzyme was thought to be a kind of glutathione S-transferase, although the purified enzyme did not show the glutathione-conjugating activity with electrophilic compounds such as 1-chloro-2,4-dinitrobenzene and o-dinitrobenzene, which are used as the substrate of glutathione S-transferase in yeast. The glutathione peroxidase in H. mrakii was then suggested to be a novel type of glutathione peroxidase in substrate specificity and intracellular localization, being different from those of other sources purified so far.

Lipid hydroperoxide-resistance gene in Saccharomyces cerevisiae: utilization as a selectable marker gene for yeast transformation

Two kinds of DNA fragments concerned with resistance against lipid hydroperoxide were cloned from the yeast Saccharomyces cerevisiae. When the recombinant plasmid carrying the DNA fragment was introduced into the cells of S. cerevisiae which do not have an appropriate auxotrophic marker, the transformants could be selected by their resistance to t-butyl hydroperoxide. By Southern hybridization analysis, such transformants were found to contain the recombinant plasmid, suggesting that the DNA fragment could be used as a selection marker for the transformation of S. cerevisiae.

Activity of urokinase diluted in 0.9% sodium chloride injection or 5% dextrose injection and stored in glass or plastic syringes

The effects of the diluent, the container, the i.v. set, and the drug concentration on the adsorption of urokinase to i.v. administration systems were studied, along with the compatibility of urokinase with plastic and glass syringes. Solutions of urokinase 1500 and 5000 IU/mL in 0.9% sodium chloride injection and 5% dextrose injection in glass and polyvinyl chloride (PVC) containers were sampled at 2 and 30 minutes. Administration sets were attached to PVC containers containing the urokinase-5% dextrose injection solutions, and samples were collected at 90 and 150 minutes. Glass and polypropylene syringes containing urokinase 5000 IU/mL in 0.9% sodium chloride injection or 5% dextrose injection were sampled at 0, 4, 8, and 24 hours. Urokinase activity was measured by an in vitro clot lysis assay. No urokinase diluted in 0.9% sodium chloride injection adsorbed to glass or PVC containers. For urokinase 1500 IU/mL in 5% dextrose injection, a loss of 15% to 20% occurred almost instantaneously in PVC containers; additional losses to the infusion sets were minimal. However, for urokinase 5000 IU/mL in 5% dextrose injection, no losses were observed in the PVC systems. No drug loss to glass bottles was seen for urokinase 1500 or 5000 IU/mL in 5% dextrose injection. Urokinase potency remained constant in polypropylene and glass syringes for 24 hours. To minimize urokinase sorption to PVC containers, higher concentrations of urokinase diluted in 5% dextrose injection should be used, provided that clinical safety and efficacy are not compromised. The use of 0.9% sodium chloride injection as a diluent also prevents sorption losses.