Precarious adolescence: Adolescent rickets and anterior sacral angulation in two Dutch skeletal collections from the 18th-19th centuries

OBJECTIVE

This project aims to provide an objective approach to suggesting cases of adolescent rickets using the presence of anterior sacral angulation and interglobular dentine.

MATERIALS

Sacra from 49 individuals from Hattem and 150 individuals from Middenbeemster, and second and third molars from five individuals from Hattem were analyzed. Both sites date to the 17th to 19th centuries.

METHODS

The sacra were visually assessed for sacral angulation and measured to quantify anterior sacral angulation. The sampled molars were thin sectioned to look for the presence of interglobular dentine.

RESULTS

Metric analysis determined that seven individuals had significantly anteriorly angled sacra. Three of the five individuals with sampled molars had interglobular dentine formed during adolescence.

CONCLUSIONS

Adolescent rickets may be associated with anterior sacral angulation.

SIGNIFICANCE

Anterior sacral angulation may help identify possible cases of adolescent rickets in archaeological human remains.

LIMITATIONS

The small sample size for the molars prevented the identification of more individuals with interglobular dentine present during adolescence. Several individuals with visibly angled sacra were unmeasurable due to post-mortem damage and lacked molars.

SUGGESTIONS FOR FURTHER RESEARCH

Research on a larger sample would allow us to understand better the association between anterior sacral angulation and adolescent rickets.

Keratin films for ocular surface reconstruction: Wound healing in an in-vivo model

The most commonly used tissue substitute for ocular surface reconstruction is human amniotic membrane (AM). Because of its low biomechanical strength and intransparency there is a need to search for alternatives of consistent quality. This study, further explored the biocompatibility of Keratin Film (KF) and its ability to sustain corneal epithelial wound healing. In three equal groups of 5 New Zeeland white rabbits a 4 mm superficial keratectomy was created in the right eye. Five eyes received a KF, five a human AM graft and the remaining five no implant. All eyes were treated with ofloxacin and dexamethasone eye drops and followed up for 10 days. Corneal fluorescein staining, vascularization, and transparency were assessed using slit lamp biomicroscopy according to a standardized grading score during and at the end of follow-up. The corneal-scleral-button was excised and processed for histology. After 10 days all eyes which had received a KF showed complete epithelial healing and no signs of neovascularization. In the AM group 1 eye showed a persistent epithelial defect at day 10 and 2 eyes showed neovascularization at day 7 resolving at day 10. Transparency improved progressively both in the KF group as well as in the AM group towards the end of the follow. Histology showed a multilayer epithelium firmly adherent to the KF with no evidence of keratocyte migration or inflammatory reaction in the corneal stroma. In this study on rabbit eyes KF better supported corneal epithelial wound healing than amniotic membrane.

DMEK after penetrating keratoplasty: cohort with DMEK grafts and descemetorhexis larger than full-thickness graft

PURPOSE

The study aims to evaluate visual outcome, central corneal thickness, and rebubbling rate in a cohort with oversized DMEK grafts after failed penetrating keratoplasty (PK). The unique feature of the study is a descemetorhexis diameter larger than the full-thickness graft, i.e., peripheral to the PK interface.

METHODS

A monocentric, retrospective evaluation of all patients with endothelial graft failure after PK treated with an oversized DMEK graft and descemetorhexis outside of the PK interface (i.e., in host tissue) between January 2015 and July 2019 at the Department of Ophthalmology at the University of Düsseldorf (Germany) was performed.

RESULTS

Eleven eyes of 10 patients were identified. Mean age was 69 years. On average (arithmetic mean ± standard deviation), 1.7 ± 1.0 previous PKs have been performed per eye in this cohort. The mean time between last PK and DMEK was 10.1 ± 7.3 years (range 2 to 23 years). In all cases, the graft diameter exceeded the diameter of the previous PK and descemetorhexis was performed in host tissue, that is, peripheral to the graft-host interface. Rebubbling was performed in 18.2% of the patients (n = 2 eyes) because of central graft detachment. Mean central corneal thickness showed a statistically significant improvement at 5.3 ± 3.5 months after surgery from 688.23 ± 151.01 to 527.75 ± 88 µm (p = 0.002). Visual acuity increased significantly by 5 lines from 1.24 ± 0.5 logMAR (range from 0.5 to 2) to 0.73 ± 0.76 logMAR (range from 0.1 to 2) within 3 months (p = 0.006). Excluding patients without visual potential and transplant failure, visual acuity improved significantly by 8 lines (p < 0.001), and stayed stable until the last follow-up at 15.1 ± 11.4 months (range 6 to 39 months, p < 0.001, n = 8) after surgery.

CONCLUSION

DMEK can be successfully used to treat endothelial cell failure after PK, and can provide good postoperative results with regards to visual acuity. This study shows that stripping of Descemet's membrane (DM) peripheral to the PK interface is surgically feasible. Overlapping, larger DMEK grafts with more endothelial cells can be used without increasing rebubbling rates and may potentially improve long-term graft survival.

A novel method for calibrating head models to account for variability in conductivity and its evaluation in a sphere model

The accuracy in electroencephalography (EEG) and combined EEG and magnetoencephalography (MEG) source reconstructions as well as in optimized transcranial electric stimulation (TES) depends on the conductive properties assigned to the head model, and most importantly on individual skull conductivity. In this study, we present an automatic pipeline to calibrate head models with respect to skull conductivity based on the reconstruction of the P20/N20 response using somatosensory evoked potentials and fields. In order to validate in a well-controlled setup without interplay with numerical errors, we evaluate the accuracy of this algorithm in a 4-layer spherical head model using realistic noise levels as well as dipole sources at different eccentricities with strengths and orientations related to somatosensory experiments. Our results show that the reference skull conductivity can be reliably reconstructed for sources resembling the generator of the P20/N20 response. In case of erroneous assumptions on scalp conductivity, the resulting skull conductivity parameter counterbalances this effect, so that EEG source reconstructions using the fitted skull conductivity parameter result in lower errors than when using the standard value. We propose an automatized procedure to calibrate head models which only relies on non-invasive modalities that are available in a standard MEG laboratory, measures under in vivo conditions and in the low frequency range of interest. Calibrated head modeling can improve EEG and combined EEG/MEG source analysis as well as optimized TES.

[Descemetectomy : An alternative to transplantation?]

Due to rising demand worldwide it is becoming increasingly more difficult to satisfy the needs for human corneal transplants. At this point transplantation is the only possible cure for endothelial diseases, such as Fuchs endothelial dystrophy. In this article we present descemetectomy, a circumscribed removal of Descemet's membrane (DMx) without subsequent transplantation, as new possible treatment option on the basis of a clinical case.

Medium-grade tubular proteinuria is common in HIV-positive patients and specifically associated with exposure to tenofovir disoproxil Fumarate

OBJECTIVES

The aim of this cross-sectional study was to evaluate the prevalence and risk factors of medium-grade proteinuria (100-500 mg/g creatinine) among HIV-positive adults.

METHODS

Spot urine samples of HIV-positive adults without known renal disease were analyzed quantitatively between January 2009 and February 2011. Demographic and medical data were collected. Multivariate regression models for different patterns of proteinuria were constructed.

RESULTS

Among 411 patients, 18 (4.4 %) presented albuminuria >300 mg/g creatinine and/or proteinuria >500 mg/g creatinine and were excluded from further analyses. Among the study population of 393 patients, 181 (46.1 %) had no significant proteinuria or albuminuria (<100 and <30 mg/g creatinine, respectively), 60 (15.3 %) had moderate albuminuria, while 152 (38.7 %) had proteinuria without albuminuria, suggesting tubular proteinuria. Independent predictors for medium-grade tubular proteinuria in multivariate analysis were exposure to tenofovir (DF), a CD4 nadir <500/µl, older age, and anti-HCV-antibodies. There was no association with classic renal risk factors like diabetes mellitus and arterial hypertension, or with estimated glomerular filtration rate (eGFR).

CONCLUSIONS

We detected significant proteinuria in 230 (56.0 %) of 411 HIV-positive patients. Among this group, 152 (66.1 %) had medium-grade proteinuria without albuminuria, which was significantly associated with exposure to tenofovir, older age, a lower CD4 nadir and Hepatitis C. Nephrologic or HIV treatment guidelines fail to detect most of these patients but rather identify patients with high cardiovascular risk. In the absence of an association with eGFR the role of medium-grade tubular proteinuria as a potential early marker of chronic kidney disease remains unclear. Prospective studies are needed.

Diagnostik von Binde- und Hornhauterkrankungen

Zytologische und histologische Methoden sind vergleichsweise selten eingesetzte, aber wichtige Hilfsmittel bei der Diagnostik von Erkrankungen der Bindehaut und Hornhaut. Die Impressionszytologie bzw. mit Bürsten gewonnene zytologische Abstriche der Konjunktiva sind einfach durchzuführen, kostengünstig und effizient. Als nicht invasive Verfahren stellen sie nur geringe Anforderungen an die Patientencompliance und das manuelle Geschick des Untersuchers. Sie können rasch in Tropfanästhesie durchgeführt und bei Bedarf problemlos wiederholt werden. Ein weiteres Mittel stellt die histologische Untersuchung dar, die im Regelfall zwar eine lokale Betäubung und Exzision erfordert, aber auch eine höhere diagnostische Aussagekraft besitzt.

[Factors influencing the measurement of tear film lipid layer thickness with interferometry]

INTRODUCTION

The quantitative measurement of the tear film lipid layer thickness is a relatively new and promising method. However, so far it has not been investigated whether there is a diurnal or a day to day variability and whether certain factors are confounding the measurement of the lipid layer thickness.

MATERIALS AND METHODS

In three different experimental settings, 10 subjects without known sicca syndrome were examined at three different time points on one day, on three different days and before and after therapeutic expression of the Meibomian glands. As a comparison, the parameters tear film break-up time, tear meniscus height, diagnostic expression of the Meibomian glands and subjective symptoms, determined using the OSDI (ocular surface disease index) questionnaire, were measured.

RESULTS

The results of the study showed a smaller variation of the lipid layer thickness measurements during the day and from day to day compared to the tear film break-up time. The expression of the Meibomian glands significantly increased the lipid layer thickness. There was a correlation between the baseline values of tear film break-up time and the lipid layer thickness.

DISCUSSION

Our data showed that the lipid layer thickness as measured with the Lipiview® interferometer appears to be a relatively constant parameter over time. In addition, the expression of the Meibomian glands could be identified as a potential confounding factor. In this study we included only healthy subjects without known sicca syndrome. For the future our findings need to be validated in dry eye patients.

Illuminating the Nubian 'Dark Age': a bioarchaeological analysis of dental non-metric traits during the Napatan Period

The origins of one of the most powerful sociopolitical entities of the Nile Valley, the Napatan State (850-650BCE), are debated. Some scholars have suggested local development of this influential Nubian State, while others propose foreign involvement. This study uses a bioarchaeological approach to examine the biological affinity of these Ancient Nubians. The focal site of this research, Tombos, is one of few non-central Napatan Period sites that have been excavated and can, therefore, shed light on the broader Napatan populace. Dental non-metric trait frequencies were examined in the Tombos sample as well as in 12 comparative samples to elucidate the biological affinities of these populations. Analyses indicate that Tombos dental non-metric trait frequencies were not significantly different from the majority of Egyptian and Nubian samples examined here. Therefore, we propose that gene flow, encouraged by long-term coexistence and intermarriage in Nubia, created an Egyptian/Nubian transcultural environment. These findings suggest the Napatan population at Tombos included descendants of Egyptians and Nubians. The Napatan Tombos sample was found to significantly differ from the latter Kushite and Meroitic samples; however, these samples are so temporally removed from the Napatan Period, we suspect subsequent episodes of population movement may have contributed to this variation.

Thoracal, abdominal and thoracoabdominal aortic aneurysm

AIM

Aortic aneurysm is a complex disease affecting males and females in a different way. We analysed gender specific differences in the abdominal (AAA), thoracal (TAA) and thoraco-abdominal (TA-AA) aortic aneurysm in patients hospitalized for aortic aneurysm (AAA) in Germany.

METHODS

Detailed lists for all patients suffering from AAA, TAA or TA-AA documented in the DRG-System as principal diagnosis in the years 2010 were provided by the Federal Statistical Office.

RESULTS

The total number of cases in males was 17,731. It was more than three time higher than in females with 4657. AAA were 6.2 time more frequent in males than in females, TAA and TA-AA only 1.6 and 1.5 times, respectively. The rates of ruptured aneurysms show a steep increase in the 9th and 10th decade which is more pronounced in females. In males there is an age dependent increase in the rate of endovascular treatment of TAA and AAA. There is no such trend in females. The rate for AAA even decreases with age. The same could be shown for more complex fenestrated or branched endoprotheses. In around 20% of all male cases with TA-AA such a design is used in the 7th to the 9th decade of life. In females such a rate is only reached in the 7th decade. In older females the rate stepwise decreased.

CONCLUSION

There are gender specific differences in the rate of rupture and endovascular treatment of AAA, TAA and TA-AA in males and females in Germany. The reasons for these differences should be elucidated in order to prove whether these differences are due to actual gender specific requirements, or simply a lack of compatibility in awareness and devices.

Wnt signalling in an in vitro niche model for conjunctival progenitor cells

Mimicking an environment in vitro that is more similar to the stem cell niche in vivo, by co-culture of mitotically active conjunctival fibroblasts (HCF) with human conjunctival epithelial cells (HCECs), improves the maintenance of epithelial cells with progenitor cell characteristics during in vitro expansion. However, little is known about the pathways controlling the fate of the epithelial progenitor cells during in vitro culture. In this study, differences in gene expression between this in vitro 'niche' model and standard culture conditions, in which growth-arrested 3 T3 feeder cells and fetal calf serum are used, were explored using a genome level microarray platform, quantitative (q)RT-PCR and western blot. The microarray analysis revealed significant alterations of biological processes involved in cell proliferation, differentiation and cell death. The analysis of stem cell-related pathways indicated changes in expression of genes involved in the Wnt signalling pathway, and further investigation by qPCR revealed significant downregulation of the Wnt ligands Wnt3, Wnt4, Wnt7B and Wnt10A, Wnt receptor proteins FZD1, LRP5, LRP6, ß-catenin and TCF7L1 and important Wnt target genes, such as CCND1, also confirmed by western blot and immunocytochemistry. The results indicate that epithelial cell expansion in the HCEC-HCF co-culture system is accompanied by significant changes in expression of genes involved in the Wnt signalling pathway. This altered pathway activation might be involved in the enhanced maintenance of epithelial progenitor cells in this in vitro 'niche' model.

[Anatomic and subjective success of structured surgical treatment strategy in the management of chronic epiphora - a postoperative analysis of contentment]

BACKGROUND

Epiphora is the result of hypersecretion or reduced tear outflow because of relative or absolute obstruction of the lacrimal system. For the treatment a specific surgical procedure is usually required. Herein we present the subjective and objective findings of 243 consecutive patients with non-irritative induced epiphora, who underwent an operation in a standardised therapy scheme, which is used at the eye departments of the Universities of Lübeck and Würzburg.

PATIENTS AND METHODS

In a retrospective cohort study 243 patients were included who underwent lateral tarsal strip (n = 72), external dacryocystorhinostomy (DCR) in the case of an absolute nasolacrimal duct obstruction (NLDO) (n = 116) and relative NLDO (n = 25), DCR with canalicular surgery (n = 18) and simple canalicular surgery (n = 12) with a follow-up of at least 6 month. Common patient and cosmetical satisfaction, intensity of symptoms and further symptoms of 168 patients were evaluated by sending a questionnaire with subsequent telephone survey. Objective findings were recorded from hospital charts.

RESULTS

59.5% of the patients were free of complaints, 19.6% had an absolute decrease of symptoms (epiphora outside and in windy weather) and 20.8 % persistent epiphora (symptoms both in- and outside persisted). 81% of patients with absolute NLDO and 57% with relative NLDO were graded as being free of symptoms, 7% (24%) as a relative decrease and 12% (19%) as a persistence of symptoms. There was a significant difference in success between these indications (p = 0.018). Patency of the lacrimal system assessed by irrigation was found in 95% (absolute NLDO). Commonly, 73.8% were satisfied, 7.7% indifferent and 18.4 % not satisfied. 4 patients were cosmetically not satisfied.

CONCLUSIONS

Use of a standardised therapy scheme reduces the symptoms in 79.1% of the patients. In patients with absolute NLDO external DCR achieves an anatomic success rate of 95% and a subjective improvement in 88% with excellent cosmetic results. In comparison with absolute NLDO the success rate of relative NLDO is lower, but still with a subjective improvement in 81%. Our results show that postoperative success depends on the preoperative cause of the epiphora.

Generation of two- and three-dimensional lacrimal gland constructs

Aqueous tear deficiency due to lacrimal gland insufficiency is one of the major causes of dry eye. In severe cases, such as Sjoegren's syndrome, Stevens-Johnson syndrome or ocular cicatricial pemphigoid, therapy with artificial tears can be insufficient to relieve severe discomfort. Engineering a lacrimal gland construct may offer a suitable alternative transplant with a tear-like secretion. However, the reconstruction of a complex structure such as the lacrimal gland is challenging, and a lacrimal gland substitute must meet several criteria. It has to contain enough functional lacrimal gland cells to produce an adequate amount of tear fluid, and a suitable matrix is needed to deliver the cells to the patient. The growing field of regenerative medicine offers promising new prospects for lacrimal gland reconstruction. This article summarizes our group's current work in developing models for lacrimal gland reconstruction, and also discusses the perspectives of a tissue-engineered lacrimal gland for future applications.

Conjunctival epithelial cells maintain stem cell properties after long-term culture and cryopreservation

Aim: Transplantation of tissue-engineered conjunctival epithelial cell sheets has proven to be a promising technique for conjunctival reconstruction. The ability to cryopreserve conjunctival epithelial cells and maintain their stem cell population would improve their availability for clinical use. The aim of this study was to evaluate whether cryopreservation and long-term in vitro culture has an effect on the proliferative capacity and the progenitor-like cell characteristics of conjunctival epithelial cells. Method: Human conjunctival cells from bulbar biopsies were isolated and expanded on a growth arrested 3T3 feeder layer. The cells were evaluated for cytokeratin (CK4/CK19) expression by immunostaining. An aliquot with half of the cells from the initial culture was frozen in liquid nitrogen and stored for 14 days and, in addition, donor cells were cryopreserved for more than 6 months (202.7 ± 13.0 days). Both cryopreserved and noncryopreserved cells were serially cultivated over four passages. For each passage the colony-forming efficiency and the cell population doubling rates were evaluated, and expression of putative progenitor cell markers, p63α and ABCG2, was assessed by immunostaining and reverse transcription PCR. Results: Both noncryopreserved and cryopreserved cells demonstrated a high colony-forming capacity that decreased with passage. Cells from both groups underwent approximately 20 cell population doublings before senescence. Immunoreactivity to p63α and ABCG2 was found in both groups until passage 4 and their presence was also confirmed by reverse transcription PCR. No difference in cell viability, colony-forming efficiency and immunoreactivity to p63α and ABCG2 was observed between cells cryopreserved for 14 days, and more than 6 months (202.7 ± 13.0 days). Conclusion: Conjunctival epithelial cells with progenitor cell-like characteristics can be efficiently cryopreserved and can subsequently maintain their function in vitro over several culture passages. The option to cryopreserve conjunctival cells prior to in vitro expansion would be an advantage when cells have to be cultivated for clinical transplantation.

Cultivation of lacrimal gland acinar cells in a microgravity environment

BACKGROUND

A rotary cell-culture system (RCCS) allows the creation of a microgravity environment of low shear force, high-mass transfer and three-dimensional cell culture of various cell types. The aim of the study was to evaluate the growth pattern and the secretory function of rabbit lacrimal gland acinar cells in a microgravity environment using an RCCS.

METHODS

Lacrimal gland acinar cells from male New Zealand White rabbits were isolated and cultured in an RCCS up to 28 days. Cells were analysed by light and electron microscopy, and apoptosis was assessed by the TUNEL assay at days 7, 14, 21 and 28. Secretory function was tested by measuring the beta-hexosaminidase activity.

RESULTS

After 7 days of culture, spheroidal aggregates were found inside the RCCS. The spheroids consisted of acinus-like cell conglomerates. Apoptotic centres inside the spheroids were observed at all time points by means of the TUNEL assay. Evaluation of the secretory function revealed beta-hexosaminidase release after carbachol stimulation which decreased over the culture period.

CONCLUSION

A simulated microgravity environment promotes the development of three-dimensional cell spheroids containing viable acinar cells up to 28 days. Due to the evolving central apoptosis, it is unlikely that such simple three-dimensional cell communities can serve as tissue equivalents for clinical transplantation, but they promise opportunities for further applications in basic and applied cell research on lacrimal gland cells.

Patient preferences among third agent HIV medications: a US and German perspective

The objective is to assess patient preferences for attributes associated with third agent HIV medications, including fosamprenavir/ritonavir (FPVr), fosamprenavir (FPV), lopinavir/ritonavir (LPVr), atazanavir (ATZ), and efavirenz (EFV). Subjects with HIV were recruited in the US and Germany to complete a computerized adaptive conjoint survey that assessed 13 attributes, including moderate to severe side effects, regimen convenience, drug resistance and efficacy. Literature on the target third-agent HIV drugs was used to identify percentage risk and severity level descriptions for each attribute. The derived preference (utility) weights for each attribute level informed the calculation of relative importance estimates for each attribute and the desirability of combinations of attributes matching the respective target third agents. The analysis included 288 HIV-positive participants (US: 132; Germany: 156), 205 of whom were treatment-experienced and 83 of whom were treatment-naïve. Of the 13 medication attributes evaluated, developing drug resistance, the risk of lipodystrophy, the risk of gastronitestinal side effects (diarrhoea, nausea and vomiting) and regimen convenience had the greatest impact on preferences. The profile based on FPVr was most preferred. Differences in the risk of developing drug resistance, risk of lipodystrophy, risk of gastrointestinal side effects and regimen convenience would likely be most influential in the perceived relative value of a third-agent medication. Physicians may wish to consider these features, especially when discussing HIV treatment options with their patients.

Amniotic membrane as a carrier for lacrimal gland acinar cells

BACKGROUND

The secretion of the lacrimal gland provides 95% of the aqueous tears, which are essential for lubrication, nutrition and protection of the ocular surface. Long-term studies of acinar lacrimal gland cells in vitro are complicated by low proliferation rate and fast loss of cell function on plastic. Aim of this study was to evaluate the growth pattern and the secretory function of lacrimal gland acinar cells on amniotic membrane (AM) in a rabbit model.

METHODS

Lacrimal gland acinar cells from Chinchilla Bastard and New Zealand White rabbits of both sexes were isolated and cultured on denuded amniotic membrane. Cells were analysed by light and electron microscopy. Secretory function was tested by measuring the beta-hexosaminidase activity.

RESULTS

Three days after seeding to the amniotic membrane, the acinar cells had attached to each other and formed small cluster. Cell clusters consisted of 2-5 cell layers, and the cells showed fine granulation in their cytoplasm, typical for secreting cells. Between days 7 and 14 cell clusters increased in size, and acini-like structures with a central lumen were found. Cells showed polarity, with a basal nucleus and apical secretory granules. Between days 21 and 28 acini-like structures were still found inside the cell clusters. Accumulation of secretory material in the central lumen and desmosome formation connecting the apical cell structures was frequently evident. However, the number of cytoplasmatic granules decreased, and on parts of the AM, cell morphology changed to flat, spindle-shaped cells with a small nucleus. Stimulation with carbachol showed a strong beta-hexosaminidase release until day 7, with a decreasing secretory function detectable until day 21.

CONCLUSION

Acinar lacrimal gland cells can be successfully cultured on amniotic membrane up to 28 days, with a secretory response to carbachol up to 21 days. This model may be used for further experimental work, to elucidate cellular mechanisms in normal and diseased lacrimal tissue.

Membrane-assisted liquid–liquid extraction coupled with gas chromatography–mass spectrometry for determination of selected polycyclic musk compounds and drugs in water samples

Selected polycyclic musk compounds and drugs were extracted from water samples by membrane-assisted micro liquid-liquid extraction. The two-phase extraction system consisted of polyethylene membrane bags filled with an organic solvent. Chloroform proved to be most suited as acceptor phase to extract caffeine, Galaxolide, Tonalide, phenazone and carbamazepine from aqueous samples. The compounds were enriched from 50 mL sample into a volume of 500 microL of chloroform. Gas chromatography-mass spectrometry (GC-MS) was applied for analysis. The extraction procedure was optimised in regard to membrane material, extraction time and temperature. The evaluation of the entire analysis protocol found limits of detection that ranged from 20 to 200 ng/L. The linear range of calibration covered one magnitude with standard deviations between 4 and 12%. Method comparison with standard analysis techniques such as solid-phase extraction (SPE) combined with GC-MS as well as LC-MS-MS confirmed this method as an easy and reliable protocol, even for the monitoring of matrix-loaded wastewater. The analysis of real samples established the feasibility of the technique.

Differential approach to the study of integral characteristics in polymer films

The differential approach is based on the determination of dimensionless differential slope, for instance, of current-voltage characteristics (IVC), I=f(V). This slope (alpha) is given by formula alpha=d(lgI)/d(lgV). With such definition the ranges of constancy of the alpha(V) dependency correspond to the part of IVC characterized by the power behaviour (I approximately V(alpha)). The differential slope of alpha(V) dependency gamma=d(lgalpha)/dlgV determines the exponent behaviour of curve (I approximately exp(eV(gamma)/kT)). Processing by the differential approach of the investigated theoretical or experimental characteristics permits us to determine the peculiarity of charge flow mechanisms, temperature behaviour of conductivity, etc. The theoretical base and some applications of differential approach to the investigation of the current-voltage, temperature and degradation characteristics of the polyaniline and poly(p-phenilenevinilene) based structures have been shown.

Nanoclusters in polymer matrices prepared by co-deposition from a gas phase

This paper reviews the fabrication of organic and metal nanoclusters in polymer matrices by three co-deposition techniques. In particular, the structure and properties of polytetrafluoroethylene (PTFE), polychlortrifluoroethylene (PCTFE), polyparaphenylene sulphide (PPS), polystyrene (PS) and polyparaxylylene (PPX) films, containing gold (Au) and dye clusters are discussed. For the first time, dye-filled polymers and multi-component films, consisting of both Au nanoparticles and dye molecules, dispersed in the PTFE matrix were studied. A low temperature plasma was used for film structure modification. Cluster formation process was studied using optical spectroscopy in situ. Transmission electron microscopy (TEM), atomic force microscopy (AFM) and ellipsometry were used for characterisation of the grown films. During Au-PTFE film growth plasmon band shifted from 460-480 nm to 560 nm. Au cluster diameter was in the 3-7 nm range. Plasma treatment of the vapours led to formation of smaller, but more aggregated clusters. During Au-PPS film deposition a two-step growth mechanism was discovered. At the beginning of film growth the plasmon band at 540 nm appeared, but as thickness increased, the band at 430 nm dominated. Without plasma treatment a disordered mixture was deposited, while with plasma treatment large Au aggregates confined with PPS matrix having plasmon band at 620 nm were formed. Dye cluster formation depends on the dye ability to aggregate, its concentration and the properties of the polymer matrix. But cluster formation can also be tuned by varying the deposition conditions. Laser beam evaporation promoted cluster formation, while plasma treatment and dilution in a polymer matrix prevented cluster formation. In all cases both equilibrium and non-equilibrium film structure can be formed using kinetic factor. Asymmetric molecules with bulky substituents were oriented in polymer matrices by applying an electric field in situ or by corona poling. These molecules did not aggregate even at high dye load. The films exhibited second harmonic generation, which demonstrated chromophore orientation in the polymer matrices.

Lowering the dose of hydroxyurea minimizes toxicity and maximizes anti-HIV potency

The goal of this study was to optimize the hydroxyurea dosage in HIV-infected patients, and to minimize the toxicity and maximize the antiviral efficacy of the hydroxyurea-didanosine combination. In a randomized, open-label study (RIGHT 702, a multicenter trial performed in private and institutional practices), three daily doses (600 microg, 800-900 microg, and 1200 microg) of hydroxyurea were administered in combination with didanosine and stavudine to 115 chronically HIV-infected patients, one-third antiretroviral drug naive, with viremia between 5000 and 200,000 copies/ml regardless of CD4+ cell count. The primary efficacy end point was the proportion of patients with plasma HIV-1 RNA levels below 400 copies/ml after 24 weeks of therapy. In the RIGHT 702 intent-to-treat population the lowest (600 mg) dose of hydroxyurea was better tolerated, associated with fewer adverse events, and more potent by all efficacy parameters, including the primary end point (76 versus 60% patients with viremia<400 copies/ml at week 24 for the 600-mg and 800- to 900-mg dose groups, respectively; p=0.027), the mean area under the curve (60.3 versus 65.8; p=0.016), and the mean log10 decrease (-1.95 versus -0.77; p=0.001). Patients receiving 600 mg of hydroxyurea daily also had the highest CD4+ cell count, CD4+/CD8+ cell ratio, and lowest CD8+ cell count and percentage (p=0.035). The RIGHT 702 trial provides an explanation for the increased toxicity and decreased efficacy of hydroxyurea when it was used at high dosage (1200 mg daily). At the optimal dosage of 600 mg daily, hydroxyurea, in combination with didanosine, deserves reevaluation for the long-term management of HIV/AIDS worldwide, because of its excellent resistance profile, durability, and affordability.

Using new structurally related additive schemes in the precalculation of gas chromatographic retention indices of polychlorinated hydroxybiphenyls on HP-5 stationary phase

A new additive scheme is proposed for the precalculation of gas chromatographic retention indices of complex organic compounds. The principal feature of this approach is the absence of previously calculated I increments for any structural fragments or functional groups in the molecule. Instead, arithmetical operations involving I values of simpler structural analogues of target compounds are used directly. I precalculation for polychlorinated hydroxybiphenyls (839 congeners) on the HP-5 stationary phase was chosen as one of the most important applications of the method under discussion. Such a large number of congeners cannot be obtained as reference samples and their gas chromatographic (GC)-mass spectrometric (MS) identification should therefore be based currently on precalculated I values.

Sequential fractionation procedure for the identification of potentially cytochrome P4501A-inducing compounds

A multistep fractionation procedure for the separation of nonpolar aromatic compounds with respect to cytochrome P4501A induction is presented. Normal-phase HPLC on nitrophenylpropyl silica and cyanopropyl silica was tested for group-specific separation as a first fractionation step. Subsequent individual compound-specific PAH fractionation was done by means of reversed-phase HPLC. Electron-donor-acceptor HPLC and size-exclusion chromatography were applied to separate PAHs, PCBs, PCNs and PCDD/Fs according to their number of aromatic carbon atoms, their hydrophobicity, their degree of chlorination, their planarity and their molecular size. The method was validated for complex environmental mixtures on the basis of two sediment extracts.