Tuning Alkaline Anion Exchange Membranes through Crosslinking: A Review of Synthetic Strategies and Property Relationships

Alkaline anion exchange membranes (AAEMs) are an enabling component for next-generation electrochemical devices, including alkaline fuel cells, water and CO2 electrolyzers, and flow batteries. While commercial systems, notably fuel cells, have traditionally relied on proton-exchange membranes, hydroxide-ion conducting AAEMs hold promise as a method to reduce cost-per-device by enabling the use of non-platinum group electrodes and cell components. AAEMs have undergone significant material development over the past two decades; however, challenges remain in the areas of durability, water management, high temperature performance, and selectivity. In this review, we survey crosslinking as a tool capable of tuning AAEM properties. While crosslinking implementations vary, they generally result in reduced water uptake and increased transport selectivity and alkaline stability. We survey synthetic methodologies for incorporating crosslinks during AAEM fabrication and highlight necessary precautions for each approach.

Additive manufacturing: Frameworks for chemical understanding and advancement in vat photopolymerization

Three-dimensional printing, or additive manufacturing (AM), is a broad term for a wide range of fabrication methods utilizing materials such as small-molecule, polymer, and metal feedstocks. Each method requires different chemical, physical, and engineering needs to be successful. This article will discuss some of the considerations for polymer-based AM methods. Ultimately, we focus on the chemistries of vat photopolymerization, in which light is used to cure a resin from liquid to solid, to provide an example of how chemical advancements have led to increased speed, resolution, and multimaterial printing capabilities not previously possible.

Refractive index matched polymeric and preceramic resins for height-scalable two-photon lithography

Nanofabrication techniques that can generate large and complex 3D structures with nanoscale features are becoming increasingly important in the fields of biomedicine, micro-optics, and microfluidics. Direct laser writing via two-photon polymerization (DLW-TPP) is one such technique that relies on nonlinear absorption of light to form nanoscale 3D features. Although DLW-TPP provides the required nanoscale resolution, its built height is often limited to less than a millimetre. This height limitation is driven by the need to tightly focus the laser beam at arbitrary depths within the photopolymer. This requirement necessitates matching the photopolymer's refractive index to specific values but the required techniques have not been disseminated widely in the open scientific literature. To address this knowledge gap, we test two universal, different approaches to generate refractive index-matched polymeric and preceramic resins and demonstrate their performance by printing of fine submicron features in 3D structures as tall as 2.5 mm. Specifically, we achieve index-matching by mixing commercially-available resins or covalent modification of functional monomers. This work investigates the relationship of voxel shape to RI mismatch, and presents tuning of RI through mixing and covalent modification to a nonconventional material system of preceramic resin which has never been demonstrated before. We demonstrate the material flexibility by generating 3D silicon oxycarbide structures from preceramic resists while simultaneously eliminating the part-height limitation of conventional DLW-TPP.

Studying the effect of resin RI on print fidelity. Chemically modifying RI resins to demonstrate 3D structures print without height limitation resulting on ceramic and nonceramic print as tall as 2.5 mm with sub-micron features.

Highly Tunable Thiol-Ene Photoresins for Volumetric Additive Manufacturing

Volumetric additive manufacturing (VAM) forms complete 3D objects in a single photocuring operation without layering defects, enabling 3D printed polymer parts with mechanical properties similar to their bulk material counterparts. This study presents the first report of VAM-printed thiol-ene resins. With well-ordered molecular networks, thiol-ene chemistry accesses polymer materials with a wide range of mechanical properties, moving VAM beyond the limitations of commonly used acrylate formulations. Since free-radical thiol-ene polymerization is not inhibited by oxygen, the nonlinear threshold response required in VAM is introduced by incorporating 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) as a radical scavenger. Tuning of the reaction kinetics is accomplished by balancing inhibitor and initiator content. Coupling this with quantitative measurements of the absorbed volumetric optical dose allows control of polymer conversion and gelation during printing. Importantly, this work thereby establishes the first comprehensive framework for spatial-temporal control over volumetric energy distribution, demonstrating structures 3D printed in thiol-ene resin by means of tomographic volumetric VAM. Mechanical characterization of this thiol-ene system, with varied ratios of isocyanurate and triethylene glycol monomers, reveals highly tunable mechanical response far more versatile than identical acrylate-based resins. This broadens the range of materials and properties available for VAM, taking another step toward high-performance printed polymers.

Reduced strain mechanochemical activation onset in microstructured materials

In this study, we show that mechanochemical activation in responsive materials with designed, periodic microstructures can be achieved at lower applied strains than their bulk counterparts.

Prolonged-Release vs Immediate-Release Tacrolimus Capsules in Black vs White Kidney Transplant Patients: A Post Hoc Analysis of Phase III Data

BACKGROUND

Black kidney transplant patients experience inferior outcomes compared with other ethnicities. Because scrutiny is required when immunosuppressant drugs are used in such at-risk populations, we report the first large-scale clinical efficacy data assessing prolonged-release tacrolimus (PR-T) in black de novo kidney transplant patients.

METHODS AND MATERIALS

We used logistic regression and proportionate hazards to compare a composite outcome measure (biopsy-proven acute rejection, graft loss, mortality, and loss to follow-up) in black and white patients in treatment groups longer than 24 weeks, from 3 large Phase III randomized controlled trials. Secondary endpoints included tacrolimus trough concentration, dose, and estimated glomerular filtration rate.

RESULTS

The study included 2162 patients whose treatments belonged to two categories (immediate-release tacrolimus: 77 black patients, 721 white patients; and PR-T: 87 black patients, 1277 white patients). Despite demographic factors generally predictive of worse outcomes, efficacy failure among black patients who received PR-T was non-inferior to that among white patients who received either therapy. Compared with immediate-release tacrolimus, black patients who received PR-T achieved stable tacrolimus concentrations 2.5 times faster (21 vs 56 days, P = .04), and more achieved stable target concentrations (76.7% vs 69.3%). Treatment-emergent adverse events were consistent with those reported separately in pivotal trials.

CONCLUSIONS

Overall, black patients who received PR-T achieved non-inferior outcomes compared to white patients, despite higher pretransplant risk among black patients. Moreover, PR-T improved the time to achieve, and the likelihood of reaching, stable therapeutic concentrations among black patients, suggesting that PR-T could improve the consistency of tacrolimus exposure in this patient population.

Modular Elastomer Photoresins for Digital Light Processing Additive Manufacturing

A series of photoresins suitable for the production of elastomeric objects via digital light processing additive manufacturing are reported. Notably, the printing procedure is readily accessible using only entry-level equipment under ambient conditions using visible light projection. The photoresin formulations were found to be modular in nature, and straightforward adjustments to the resin components enabled access to a range of compositions and mechanical properties. Collectively, the series includes silicones, hydrogels, and hybrids thereof. Printed test specimens displayed maximum elongations of up to 472% under tensile load, a tunable swelling behavior in water, and Shore A hardness values from 13.7 to 33.3. A combination of the resins was used to print a functional multimaterial three-armed pneumatic gripper. These photoresins could be transformative to advanced prototyping applications such as simulated human tissues, stimuli-responsive materials, wearable devices, and soft robotics.

Production of Materials with Spatially-Controlled Cross-Link Density via Vat Photopolymerization

We describe an efficient method to produce objects comprising spatially controlled and graded cross-link densities using vat photopolymerization additive manufacturing (AM). Using a commercially available diacrylate-based photoresin, 3D printer, and digital light processing (DLP) projector, we projected grayscale images to print objects in which the varied light intensity was correlated to controlled cross-link densities and associated mechanical properties. Cylinder and bar test specimens were used to establish correlations between light intensities used for printing and cross-link density in the resulting specimens. Mechanical testing of octet truss unit cells in which the properties of the crossbars and vertices were independently modified revealed unique mechanical responses from the different compositions. From the various test geometries, we measured changes in mechanical properties such as increased strain-to-break in inhomogeneous structures in comparison with homogeneous variants.

Micropollutants in urban stormwater: occurrence, concentrations, and atmospheric contributions for a wide range of contaminants in three French catchments

This study aimed at: (a) providing information on the occurrence and concentration ranges in urban stormwater for a wide array of pollutants (n = 77); (b) assessing whether despite the differences between various catchments (land use, climatic conditions, etc.), the trends in terms of contamination level are similar; and (c) analyzing the contribution of total atmospheric fallout (TAF) with respect to sources endogenous to this contamination. The studied contaminants include conventional stormwater contaminants (polycyclic aromatic hydrocarbons (PAHs), Zn, Cu, Pb, etc.), in addition to poorly or undocumented pollutants such as nonylphenol and octylphenol ethoxylates (NPnEO and OPnEO), bisphenol A (BPA), polybrominated diphenyl ethers (PBDEs), a wide variety of pesticides, and various metals of relevance (As, Ti, Sr, V). Sampling and analysis were performed using homogeneous methods on three urban catchments with different land use patterns located in three distinct French towns. For many of these pollutants, the results do not allow highlighting a significant difference in stormwater quality at the scale of the three urban catchments considered. Significant differences were, however, observed for several metals (As, Cr, Cu, Ni, Sr and Zn), PAHs, and PBDEs, though this assessment would need to be confirmed by further experiments. The pollutant distributions between dissolved and particulate phases were found to be similar across the three experimental sites, thus suggesting no site dependence. Lastly, the contributions of TAF to stormwater contamination for micropollutants were quite low. This finding held true not only for PAHs, as previously demonstrated in the literature, but also for a broader range of molecules such as BPA, NPnEO, OPnEO, and PBDEs, whose high local production is correlated with the leaching of urban surfaces, buildings, and vehicles.

Use of argatroban during multi-organ procurement: pharmacokinetics and sequelae in recipient of transplanted liver

This report illustrates potential concerns regarding the administration of Argatroban (AGN), a small molecule, direct thrombin inhibitor, within the setting of multi-organ procurement (MOP). Herein, we outline the case of a large AGN bolus to the donor during MOP, and the passive transfer of a coagulopathy to the recipient of the transplanted liver. From this, we conclude that caution should be exercised when AGN is used in the setting of MOP.

Gas 6 promotes Axl-mediated survival in pulmonary endothelial cells

We examined Gas 6-Axl interactions in human pulmonary artery endothelial cells (HPAEC) and in Axl-transduced HPAEC to test Gas 6 function during endothelial cell survival. We identified the 5.0-kb Axl, 4.2-kb Rse, and 2.6-kb Gas 6 mRNAs in HPAEC. Immunoprecipitation and Western blotting confirmed the presence of these proteins. Gas 6 is present in cell-associated and secreted fractions of growth-arrested HPAEC, independent of cell density. In addition, the Axl receptor is constitutively phosphorylated in growth-arrested cultures, and exogenous Gas 6 enhanced Axl phosphorylation threefold. Gas 6 added to growth-arrested HPAEC resulted in a significant increase in cell number (1.5 nM Gas 6 increased cell number 35%). Flow cytometry revealed that Gas 6 treatment resulted in 28% fewer apoptosing cells. Transduction of a full-length Axl cDNA into HPAEC resulted in 54% fewer apoptosing cells after Gas 6 treatment. Collectively, the data demonstrate antiapoptotic activities for Gas 6 in HPAEC and suggest that Gas 6 signaling may be relevant to endothelial cell survival in the quiescent environment of the vessel wall.

The effect of precursor structures on the action of glucosaminyl 3-O-sulfotransferase-1 and the biosynthesis of anticoagulant heparan sulfate

To understand how 2-O-sulfation of uronic acid residues influences the biosynthesis of anticoagulant heparan sulfate, the cDNA encoding glucosaminyl 3-O-sulfotransferase-1 (3-OST-1) was introduced into wild-type Chinese hamster ovary cells and mutant pgsF-17 cells, which are defective in 2-O-sulfation. 3-OST-1-transduced cells gained the ability to bind to antithrombin. Structural analysis of the heparan sulfate chains showed that 3-OST-1 generates sequences containing GlcUA-GlcN(SO(3))3(SO(3)) and GlcUA-GlcN(SO(3))3(SO(3))6(SO(3)) in both wild-type and mutant cells. In addition, IdoUA-GlcN(SO(3))3(SO(3)) and IdoUA-GlcN(SO(3))3(SO(3))6(SO(3)) accumulate in the mutant chain. These disaccharides were also observed by tagging [6-(3)H]GlcN-labeled pgsF-17 heparan sulfate in vitro with [(35)S]PAPs and purified 3-OST-1. Heparan sulfate derived from the transduced mutant also had approximately 2-fold higher affinity for antithrombin than heparan sulfate derived from the transduced wild-type cells, and it inactivated factor Xa more efficiently. This study demonstrates for the first time that (i) 3-O-sulfation by 3-OST-1 can occur independently of the 2-O-sulfation of uronic acids, (ii) 2-O-sulfation usually occurs before 3-O-sulfation, (iii) 2-O-sulfation blocks the action of 3-OST-1 at glucosamine residues located to the reducing side of IdoUA units, and (iv) that alternative antithrombin-binding structures can be made in the absence of 2-O-sulfation.

Peptide-mediated cellular delivery

Peptide-mediated molecular therapeutic delivery systems have recently emerged as an alternative means to effectively substitute or augment present gene therapy technologies, e.g., TAT, VP22, engineered peptides. These systems show great promise for the elimination of the main bottleneck to safe, efficient, targeted gene therapy delivery and are able to efficiently introduce DNA, antisense peptide nucleic acids, oligonucleotides, small molecules and proteins into cells both in vitro and in vivo. They are versatile and easily designed to incorporate a number of specific attributes required for efficient cargo delivery. A fundamentally new property of these moieties will allow the therapeutic intervention in the biochemistry of the target cell without the need to alter its genome.

The role of syndecan cytoplasmic domain in basic fibroblast growth factor-dependent signal transduction

To determine the role played by syndecan-4 cytoplasmic domain in the mediation of basic fibroblast growth factor (bFGF) signaling, immortalized human cells (ECV) were used to generate cell lines expressing constructs encoding full-length sequences for syndecan-4 (S4), syndecan-1 (S1), glypican-1 (G1), or chimeric proteins consisting of the ectoplasmic domain of glypican-1 linked to the transmembrane/cytoplasmic domain of syndecan-4 (G1-S4c) and the ectoplasmic domain of syndecan-4 linked to the glypican-1 glycosylphosphatidylinositol (GPI) anchor sequence (S4-GPI). Vector-transduced cells (VC) were used as controls. Expression of all these proteoglycans (except for the vector control) significantly increased cell-associated heparan sulfate mass and the number of low affinity bFGF-binding sites. However, in low serum medium, the addition of bFGF stimulated growth and migration of cells expressing S4 and G1-S4c constructs but not G1, S1, S4-GPI, or VC cells. Similar results were obtained using Matrigel growth assays. Mutations of heparan sulfate attachment sites on S4 construct abolished syndecan-4-dependent augmentation of bFGF responses. We conclude that cytoplasmic tail of syndecan-4 plays an important role in bFGF-mediated signal transduction.

Expression of heparan sulfate D-glucosaminyl 3-O-sulfotransferase isoforms reveals novel substrate specificities

The 3-O-sulfation of glucosamine residues is an important modification during the biosynthesis of heparan sulfate (HS). Our previous studies have led us to purify and molecularly clone the heparan sulfate D-glucosaminyl 3-O-sulfotransferase (3-OST-1), which is the key enzyme converting nonanticoagulant heparan sulfate (HSinact) to anticoagulant heparan sulfate (HSact). In this study, we expressed and characterized the full-length cDNAs of 3-OST-1 homologous genes, designated as 3-OST-2, 3-OST-3A, and 3-OST-3B as described in the accompanying paper (Shworak, N. W., Liu, J., Petros, L. M., Zhang, L., Kobayashi, M., Copeland, N. G., Jenkins, N. A., and Rosenberg, R. D. (1999) J. Biol. Chem. 274, 5170-5184). All these cDNAs were successfully expressed in COS-7 cells, and heparan sulfate sulfotransferase activities were found in the cell extracts. We demonstrated that 3-OST-2, 3-OST-3A, and 3-OST-3B are heparan sulfate D-glucosaminyl 3-O-sulfotransferases because the enzymes transfer sulfate from adenosine 3'-phosphophate 5'-phospho-[35S]sulfate ([35S]PAPS) to the 3-OH position of glucosamine. 3-OST-3A and 3-OST-3B sulfate an identical disaccharide. HSact conversion activity in the cell extract transfected by 3-OST-1 was shown to be 300-fold greater than that in the cell extracts transfected by 3-OST-2 and 3-OST-3A, suggesting that 3-OST-2 and 3-OST-3A do not make HSact. The results of the disaccharide analysis of the nitrous acid-degraded [35S]HS suggested that 3-OST-2 transfers sulfate to GlcA2S-GlcNS and IdoA2S-GlcNS; 3-OST-3A transfers sulfate to IdoA2S-GlcNS. Our results demonstrate that the 3-O-sulfation of glucosamine is generated by different isoforms depending on the saccharide structures around the modified glucosamine residue. This discovery has provided evidence for a new cellular mechanism for generating a defined saccharide sequence in structurally complex HS polysaccharide.

Expression cloning of LDLB, a gene essential for normal Golgi function and assembly of the ldlCp complex

The Chinese hamster ovary (CHO) cell mutants ldlC and ldlB, which exhibit almost identical phenotypes, define two genes required for multiple steps in the normal medial and trans Golgi-associated processing of glycoconjugates. The LDLC gene encodes ldlCp, an approximately 80-kDa protein, which in wild-type, but not ldlB, cells associates reversibly with the cytoplasmic surface of the Golgi apparatus. Here, we have used a retrovirus-based expression cloning system to clone a murine cDNA, LDLB, that corrects the pleiotropic mutant phenotypes of ldlB cells. The corresponding mRNA was not detected in ldlB mutants. LDLB encodes an approximately 110-kDa protein, ldlBp, which lacks homology to known proteins and contains no common structural motifs. Database searches identified short segments of homology to sequences from Drosophila melanogaster, Arabidopsis thaliana, and Caenorhabditis elegans, and the essentially full-length homologous human sequence (82% identity); however, as was the case for ldlCp, no homologue was identified in Saccharomyces cerevisiae. We have found that in wild-type cell cytosols, ldlCp is a component of an approximately 950-kDa "ldlCp complex," which is smaller, approximately 700 kDa, in ldlB cytosols. Normal assembly of this complex is ldlBp-dependent and may be required for Golgi association of ldlCp and for the normal activities of multiple luminal Golgi processes.

The retinoic acid and cAMP-dependent up-regulation of 3-O-sulfotransferase-1 leads to a dramatic augmentation of anticoagulantly active heparan sulfate biosynthesis in F9 embryonal carcinoma cells

Retinoic acid (RA) and dibutyryl cAMP plus theophilline (CT) trigger F9 cells to differentiate into parietal endoderm. The differentiation induces a 9-fold increase in total heparan sulfate (HStotal) biosynthesis and a 170-fold increase in anticoagulantly active HS (HSact) biosynthesis. Measurement of 3-O-sulfotransferase-1 mRNA and enzymatic activity demonstrated an increase of over 100-fold whereas determination of N-, 2-O, and 6-O-sulfotransferase enzymatic activities showed elevations of 2-, 3. 5-, and 3.7-fold, respectively. HSact precursor pool measurements reveal that 30% of control F9 HStotal can be converted into HSact while only an additional 10% of RACT F9 HStotal can be transformed into HSact. Disaccharide analysis of metabolic labeled HS indicated that 32% 3-O-sulfate containing disaccharides, i.e. GlcA-anManR3S and GlcA-anManR3S6S, are present in HSact and 68% GlcA-anManR3S and GlcA-anManR3S6S are found in anticoagulantly inactive HS (HSinact). By using adenosine 3'-phosphate 5'-phosphosulfate and purified 3-O-sulfotransferase-1, 30% of 3-O-sulfation occurs in HSact and 70% of 3-O-sulfation occurs in HSinact. The similar ratio of 3-O-sulfate distribution in HSact versus HSinact suggests that HSact production in the F9 system is determined by the abundance of 3-O-sulfotransferase-1 as well as the size of the HSact precursor pool. Extensively 3-O-sulfated HSinact may play an important functional role under in vivo conditions within the murine placenta.

The neuroethology of frequency preferences in the spring peeper

We studied the relationship between auditory activity in the midbrain and selective phonotaxis in females of the treefrog, Pseudacris crucifer. Gravid females were tested in two-stimulus playback tests using synthetic advertisement calls of different frequencies (2600 versus 2875 Hz; 2800 versus 3500 Hz; 2600 versus 3500 Hz). Tests were conducted with and without a background of synthesized noise, which was filtered to resemble the spectrum of a chorus of spring peepers. There were no significant preferences for calls of any frequency in the absence of background noise. With background noise, females preferred calls of 3500 Hz to those of 2600 Hz. Multi-unit recordings of neural responses to synthetic sounds were made from the torus semicircularis of the same females following the tests of phonotaxis. We measured auditory threshold at 25 frequencies (1800-4200 Hz) as well as the magnitude of the neural response when stimulus amplitude was held constant and frequency was varied. This procedure yielded isointensity response contours, which we obtained at six amplitudes in the absence of noise and at the stimulus amplitude used during the phonotaxis tests with background noise. Individual differences in audiograms and isointensity responses were poorly correlated with behavioural data except for the test of 2600 Hz versus 3500 Hz calls in noise. The shape of the neural response contours changed with stimulus amplitude and in the presence of the simulated frog chorus. At 85 dB sound pressure level (SPL), the level at which females were tested, the contours of females were quite flat. The contours were more peaked at lower SPLs as well as during the broadcast of chorus noise and white noise at an equivalent spectrum level (45-46 dB/Hz). Peaks in the isointensity response plots of most females occurred at stimulus frequencies ranging from 3200 to 3400 Hz, frequencies close to the median best excitatory frequency (BEF) of 3357 Hz but higher than the mean of the mid-frequency of the male advertisement call (3011 Hz). Addition of background noise may cause a shift in the neural response-intensity level functions. Our results highlight the well-known nonlinearity of the auditory system and the danger inherent in focusing solely on threshold measures of auditory sensitivity when studying the proximate basis of female choice. The results also show an unexpected effect of the natural and noisy acoustic environment on behaviour and responses of the auditory system. Copyright 1998 The Association for the Study of Animal Behaviour.

Molecular cloning and expression of mouse and human cDNAs encoding heparan sulfate D-glucosaminyl 3-O-sulfotransferase

The cellular rate of anticoagulant heparan sulfate proteoglycan (HSPGact) generation is determined by the level of a kinetically limiting microsomal activity, HSact conversion activity, which is predominantly composed of the long sought heparan sulfate D-glucosaminyl 3-O-sulfotransferase (3-OST) (Shworak, N. W., Fritze, L. M. S., Liu, J., Butler, L. D., and Rosenberg, R. D. (1996) J. Biol. Chem. 271, 27063-27071; Liu, J., Shworak, N. W., Fritze, L. M. S., Edelberg, J. M., and Rosenberg, R. D. (1996) J. Biol. Chem. 271, 27072-27082). Mouse 3-OST cDNAs were isolated by proteolyzing the purified enzyme with Lys-C, sequencing the resultant peptides as well as the existing amino terminus, employing degenerate polymerase chain reaction primers corresponding to the sequences of the peptides as well as the amino terminus to amplify a fragment from LTA cDNA, and utilizing the resultant probe to obtain full-length enzyme cDNAs from a lambda Zap Express LTA cDNA library. Human 3-OST cDNAs were isolated by searching the expressed sequence tag data bank with the mouse sequence, identifying a partial-length human cDNA and utilizing the clone as a probe to isolate a full-length enzyme cDNA from a lambda TriplEx human brain cDNA library. The expression of wild-type mouse 3-OST as well as protein A-tagged mouse enzyme by transient transfection of COS-7 cells and the expression of both wild-type mouse and human 3-OST by in vitro transcription/translation demonstrate that the two cDNAs directly encode both HSact conversion and 3-OST activities. The mouse 3-OST cDNAs exhibit three different size classes because of a 5'-untranslated region of variable length, which results from the insertion of 0-1629 base pairs (bp) between residues 216 and 217; however, all cDNAs contain the same open reading frame of 933 bp. The length of the 3'-untranslated region ranges from 301 to 430 bp. The nucleic acid sequence of mouse and human 3-OST cDNAs are approximately 85% similar, encoding novel 311- and 307-amino acid proteins of 35,876 and 35,750 daltons, respectively, that are 93% similar. The encoded enzymes are predicted to be intraluminal Golgi residents, presumably interacting via their C-terminal regions with an integral membrane protein. Both 3-OST species exhibit five potential N-glycosylation sites, which account for the apparent discrepancy between the molecular masses of the encoded enzyme (approximately 34 kDa) and the previously purified enzyme (approximately 46 kDa). The two 3-OST species also exhibit approximately 50% similarity with all previously identified forms of the heparan biosynthetic enzyme N-deacetylase/N-sulfotransferase, which suggests that heparan biosynthetic enzymes share a common sulfotransferase domain.

Analysis of 2-difluoromethyl-DL-ornithine in human plasma, cerebrospinal fluid and urine by cation-exchange high-performance liquid chromatography

An analytical method has been developed based on cation-exchange liquid chromatography for the measurement of 2-difluoromethyl-DT-ornithine (DFMO) in human plasma, cerebrospinal fluid (CSF) and urine. Fluorescence detection at excitation/emission wavelengths of 340/440 nm is followed by postcolumn derivatization with o-phthalaldehyde-2,mercaptoethanol. All calibration ranges yielded linear relationships with correlation coefficients better than 0.999. In each case the limit of quantitation was equal to the lowest value of the standard curve. The variability of the assay, expressed as relative standard deviations, was less than 7.1%, 15.3% and 7.1% for plasma, CSF and urine, respectively. The accuracy of the assay (expressed as relative errors) ranged between 4.3% and 2.0% for plasma analysis, between -0.1% and 14.0% for CSF analysis and between -8.0% and 2.0% for urine analysis. Plasma, CSF and urinary DFMO concentrations were measured in samples obtained from patients undergoing treatment for trypanosomiasis. The method was found to be applicable for the measurement of DFMO levels in human body fluids for the determination of pharmacokinetic parameters in clinical studies.

Simultaneous measurement of dolasetron and its major metabolite, MDL 74,156, in human plasma and urine

A selective and sensitive analytical method for the simultaneous measurement of dolasetron (I) and its major metabolite, MDL 74,156 (II), in human plasma and urine samples has been developed using a structural analogue. MDL 101,858, as internal standard (I.S.). The compounds were extracted from plasma and urine using solvent extraction after the addition of the I.S. Chromatographic separation was carried out on a reversed-phase HPLC column and detection and quantification was by fluorescence with excitation and emission wavelengths of 285 and 345 nm, respectively. Linear responses were obtained over concentration ranges of 5 to 1000 pmol/ml for plasma samples and 20 to 1000 pmol/ml for urine samples with correlation coefficients for the calibration curves exceeding 0.999 in all cases. Intra-day and inter-day reproducibility yielded limits of quantification of 10 pmol/ml for I and 5 pmol/ml for II plasma and 50 pmol/ml for I and II in urine. The method has been applied to the simultaneous analysis of both compounds in plasma and urine samples coming from clinical pharmacokinetic studies.

Sequence analysis of the ribosomal RNA operon of the Lyme disease spirochete, Borrelia burgdorferi

An 11,955-bp region of the Borrelia burgdorferi chromosome containing all the genes encoding ribosomal RNA (rRNA) has been sequenced. The region contains a single gene encoding 16S rRNA and two genes encoding the 23S and 5S rRNAs. The sizes of the 16S, 23S and 5S rRNAs encoded by these genes are 1537, 2926 and 112 nucleotides, respectively. In addition, the genes encoding tRNA(Ala) and tRNA(Ile) are located in the intergenic spacer between the 16S and 23S rDNAs. The tDNAs do not encode the common CCA 3' end which presumably must be added posttranscriptionally. All the genes are present in the same orientation, except for that encoding tRNA(Ile), which is transcribed from the opposite strand. The latter implies that the rDNAs are not transcribed as a single unit. The location of putative promoters and termination signals in the sequence suggest that the 16S rRNA and tRNA(Ala) are transcribed as a single unit, tRNA(Ile) is produced as an individual transcript and the 23S and 5S rDNAs are co-transcribed. Several of the features of this rDNA organization are unique, not having been described previously in any other eubacteria.

Base sequence selectivity in the binding of 7(R),8(S)-dihydroxy-9(S),10(R)-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene to oligodeoxyribonucleotide duplexes

The effect of nucleotide sequence on the binding of 7(R),8(S)-dihydroxy-9(S),10(R)-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene [(+)-anti-BPDE] to the exocyclic amino group of deoxyguanosine was investigated in duplexes formed by self-complementary oligodeoxyribonucleotide decamers which contained two deoxyguanosines (dGs) within unique sequences. A 35S-postlabeling procedure was developed for analysis of (+)-anti-BPDE adducts as dinucleotides containing 5'-(+)-anti-BPDE-dG adducts. This allows identification of the 3' neighbor of the reacted guanine and permits quantitation of the binding of (+)-anti-BPDE to each specific guanine in the oligodeoxyribonucleotide duplexes. Of all the central dG-containing sequences studied, dG surrounded by deoxycytidines (CGC) reacted to the greatest extent: over 4-fold more (+)-anti-BPDE bound to this central dG compared to the least reactive deoxyguanosine (AGT). (+)-anti-BPDE exhibited a preference for binding to a central deoxyguanosine when either the 5' or 3' neighbor was deoxyguanosine. The binding of (+)-anti-BPDE to oligodeoxyribonucleotide duplexes containing different numbers of consecutive dGs was analyzed in order to determine how the length of these sequences influences binding. Increases in the length of consecutive deoxyguanosine residues from 3 to 5 had little effect on the quantity of (+)-anti-BPDE bound to dG above that expected from the presence of a neighboring dG and an increase in the number of dG residues available for reaction. The results obtained with these oligodeoxyribonucleotide duplexes were consistent with the data available for the reaction of (+)-anti-BPDE with DNA, indicating that these duplexes are a valuable model for studying the effect of base sequence on the interaction of BPDE isomers with DNA. The dinucleotide postlabeling technique developed for these studies, with appropriate oligodeoxyribonucleotides and chromatographic conditions, will be useful for determining the effect of base sequence on the binding of other hydrocarbon diol epoxides as well as other reactive hydrocarbon metabolites to deoxyguanosine or deoxyadenosine in oligodeoxyribonucleotide duplexes and fragments of DNA.

Molecular cloning and sequencing of infC, the gene encoding translation initiation factor IF3, from four enterobacterial species

Translation initiation factor IF3 plays a crucial role in initiation of protein synthesis in bacteria. In order to elucidate the IF3 structural elements required for these functions, the evolutionary conservation of IF3 and its gene, infC, was investigated. Homologous infC sequences from Salmonella typhimurium, Klebsiella pneumoniae, Serratia marcescens and Proteus vulgaris were amplified by the polymerase chain reaction and sequenced. Analysis of these sequences, as well as that from Bacillus stearothermophilus, revealed several regions (e.g. residues 62-73 and 173-177) of absolute sequence conservation, suggesting an important role for these regions in IF3 function.

Diagnosis of early Lyme disease by polymerase chain reaction amplification and culture of skin biopsies from erythema migrans lesions

Current laboratory diagnosis of Lyme disease relies on tests for the detection of antibodies to Borrelia burgdorferi, the etiologic agent of the disease. These tests are often unreliable because of a lack of sensitivity and specificity and test-to-test variability. The purpose of this study was to evaluate the sensitivity and specificity of polymerase chain reaction (PCR) amplification for detection of B. burgdorferi in skin biopsy specimens. Forty-six 2-mm skin biopsy samples were obtained from 44 patients with a clinical diagnosis of erythema migrans, 9 of whom were receiving antibiotic therapy at the time of biopsy. Specimens were ground in BSK medium with separate aliquots taken for culture and PCR. Of the specimens from the untreated group, 57% (21 of 37) were positive by culture and 22% (8 of 37) were culture negative; 22% (8 of 37) of the cultures were uninformative because of contamination. By comparison, 22 (59%) of 37 specimens were positive by PCR amplification. Of 21 culture-positive samples, 13 (62%) were also positive by PCR analysis. Thus, the sensitivity of the PCR was 59 to 62%, based on either a clinical or cultural diagnosis of untreated Lyme disease. None of the nine specimens from antibiotic-treated patients grew in culture, whereas two of the nine were positive by PCR analysis. Given the complexity and time required for culture, PCR is a promising technique for the diagnosis of early Lyme disease.

Molluscum contagiosum in patients with human immunodeficiency virus infection

BACKGROUND

Molluscum contagiosum (MC) is a common and at times severely disfiguring cutaneous viral infection in patients with human immunodeficiency virus (HIV) infection.

OBJECTIVE

The purpose of this study was to describe the clinical course of MC in patients with HIV infection and to examine the relation between presentation of MC and the stage of HIV infection, as measured by T-cell subsets.

METHODS

This is a retrospective case study of 27 patients with MC and HIV infection who had T-cell subset determination within 60 days of diagnosis of MC.

RESULTS

The overall mean CD4+ count, CD4+ percentage, and CD4+/CD8+ ratio were 85.7/mm3, 5.9%, and 0.10, respectively. An inverse relation between CD4+ count and the number of MC lesions was observed (p = 0.0023). Fourteen patients (52%) had facial and neck lesions alone, and seven (26%) had lesions in areas associated with sexual transmission. Pneumocystis carinii pneumonia had occurred in 8 patients (31%) and Kaposi's sarcoma in 15 patients (56%).

CONCLUSION

MC can occur as a late manifestation of HIV infection and is a cutaneous correlate of cellular immune deficiency.

rRNA gene organization in the Lyme disease spirochete, Borrelia burgdorferi

Lyme disease is the most common vector-borne disease in the United States. The causative agent is the spirochete Borrelia burgdorferi. The copy number and organization of the genes encoding the rRNAs of this organism were determined. There is a single gene for 16S rRNA and two copies each of the 23S rRNA and 5S rRNA genes. All of the genes are located within a chromosomal fragment of approximately 9.5 to 10.0 kb. The 23S and 5S rRNA genes are tandemly duplicated in the order 23S-5S-23S-5S and are apparently not linked to the 16S rRNA gene, which is situated over 2 kb upstream from the 23S-5S duplication. The individual copies of the 23S-5S duplication are separated by a 182-bp spacer. Within each 23S-5S unit, an identical 22-bp spacer separates the 23S and 5S rRNA sequences from each other. The genome organization of the 23S-5S gene cluster in a number of different B. burgdorferi isolates obtained at a number of different geographical locations, as well as in several other species of Borrelia, was investigated. All isolates of B. burgdorferi tested displayed the tandem duplication, whereas the closely related species B. hermsii, B. anserina, and B. turicatae all contained a single copy of each of the genes. In addition, different geographical isolates of B. burgdorferi can be differentiated on the basis of a restriction fragment length polymorphism associated with the 23S-5S gene cluster. This polymorphism can be a useful tool for the determination of genetic relatedness between different isolates of B. burgdorferi.

Assessing civil competence in the elderly

This study was designed to establish reliability of the Community Competence Scale-Revised (CCS-R) and provide evidence for its validity in making discriminations relevant to civil competence in the elderly. The CCS-R is an individually administered structured interview of 17 subscales. Criterion groups were formed by drawing a sample of research participants from a retirement complex with various levels of care and with nurses having extensive knowledge of the residents' level of functioning. The study demonstrated high reliability and found converging evidence for the effectiveness of the CCS-R in making discrimination about competence in the elderly. The study had added to the growing evidence that it is possible to standardize the assessment of civil competence, thereby making the adjudication process a more accurate one.

HIV-related malignancies

Since the recognition of Kaposi's sarcoma as a manifestation of the acquired immunodeficiency syndrome, subsequent malignancies such as non-Hodgkin's B-cell lymphoma and primary central nervous system lymphoma have been found to be associated with individuals infected with the human immunodeficiency virus (HIV). The epidemiology, clinical manifestations, and current concepts of pathogenesis are reviewed in this article. In addition, the relation between HIV and other malignancies, including Hodgkin's lymphoma, T-cell lymphomas, and anorectal carcinoma, is discussed. In general, HIV-related malignancies are more aggressive, respond poorly to treatment, and are associated with an extremely high rate of mortality.

Unexpected geographic variation in rates of hospitalization for patients who have fracture of the hip. Medicare enrollees in the United States

With the use of data from hospitals for fiscal year 1985, we calculated the rates of hospitalization for fracture of the hip, by state of residence, for all enrollees in Medicare who were sixty-five years old or older; we adjusted for age and race. The rate of fracture of the hip was highest in the South and lowest in the Northeast, especially in women. The cause of this difference is not known.

Female green treefrogs (Hyla cinerea) do not selectively respond to signals with a harmonic structure in noise

1. Females of the green treefrog, Hyla cinerea, communicate in noisy environments, with spectrally complicated signals. A previous study (Megela Simmons 1988), using the reflex modification technique, found that the masked threshold of green treefrogs to two-tone signals differed by about 10 dB depending on whether or not the two components were harmonically-related. The present study used the same two-component stimuli to test the prediction that gravid females would better detect harmonic sounds in noise than inharmonic ones. 2. We offered gravid treefrogs simultaneous choices between alternative two-component synthetic sounds: (1) an inharmonic sound of 831 + 3100 Hz, and a harmonic sound of 828 + 2760 Hz. We varied the sound pressure level (SPL in decibels [dB]) to which we equalized these alternatives at the female's release point (75 and 80 dB SPL), and we tested females in quiet conditions and in the presence of broadband background noise (52 dB/Hz at the female's release point). 3. At a signal playback level of 75 dB SPL, one-third of the females responded in the presence of background noise. Subtracting the spectrum level yields a critical ratio estimate of 23 dB, a value that is very similar to estimates for single pure tones in noise reported in other studies of this species (Ehret and Gerhardt 1980; Moss and Megela Simmons 1986). Females did not, however, choose the harmonic sound over the inharmonic sound in this condition, at the higher signal-to-noise ratio, or in either of the unmasked situations.(ABSTRACT TRUNCATED AT 250 WORDS)

Encoding of a spectrally-complex communication sound in the bullfrog's auditory nerve

1. A population study of eighth nerve responses in the bullfrog, Rana catesbeiana, was undertaken to analyze how the eighth nerve codes the complex spectral and temporal structure of the species-specific advertisement call over a biologically-realistic range of intensities. Synthetic advertisement calls were generated by Fourier synthesis and presented to individual eighth nerve fibers of anesthetized bullfrogs. Fiber responses were analyzed by calculating rate responses based on post-stimulus-time (PST) histograms and temporal responses based on Fourier transforms of period histograms. 2. At stimulus intensities of 70 and 80 dB SPL, normalized rate responses provide a fairly good representation of the complex spectral structure of the stimulus, particularly in the low- and mid-frequency range. At higher intensities, rate responses saturate, and very little of the spectral structure of the complex stimulus can be seen in the profile of rate responses of the population. 3. Both AP and BP fibers phase-lock strongly to the fundamental (100 Hz) of the complex stimulus. These effects are relatively resistant to changes in stimulus intensity. Only a small number of fibers synchronize to the low-frequency spectral energy in the stimulus. The underlying spectral complexity of the stimulus is not accurately reflected in the timing of fiber firing, presumably because firing is 'captured' by the fundamental frequency. 4. Plots of average localized synchronized rate (ALSR), which combine both spectral and temporal information, show a similar, low-pass shape at all stimulus intensities. ALSR plots do not generally provide an accurate representation of the structure of the advertisement call. 5. The data suggest that anuran peripheral auditory fibers may be particularly sensitive to the amplitude envelope of sounds.

Preparation of human cord sera for enzymatic triglyceride assays: removal of free glycerol by ultrafiltration

Enzymatic triglyceride assays that generate glycerol from triglycerides as a part of the enzymatic process in quantitating serum triglyceride levels give elevated values when external free glycerol is present. Our objective was to develop an ultrafiltration technique that would remove exogenous and/or endogenous free glycerol from small aliquots of human cord sera so that accurate serum triglyceride values could be obtained with the commercially available triglyceride assay kits. Exogenous glycerol was completely removed from cord sera when the samples were washed twice with saline in Amicon Centricon-30 microconcentrators. This ultrafiltration technique lowered cord serum triglyceride levels significantly (P less than 0.001), but had no effect on cord total serum cholesterol levels. A comparison of washed and unwashed cord sera by either polyacrylamide or agarose gel electrophoresis indicated that the serum protein and lipoprotein profiles were not altered by the ultrafiltration process.

2-Pyrrolidinone in human cerebrospinal fluid: a major constituent of total gamma-aminobutyric acid

2-Pyrrolidinone, the lactam of gamma-aminobutyric acid (GABA), is identified as the major constituent of total GABA in human CSF. Structural elucidation was done by mass spectrometry. In lumbar CSF of four patients, 2-pyrrolidinone represented about 54% of GABA found after acid hydrolysis, thus accounting for essentially all of the hitherto unknown GABA fraction in CSF.

Expression of Escherichia coli infC: identification of a promoter in an upstream thrS coding sequence

infC, the gene which codes for translation initiation factor 3, is situated in a cluster in the genome of Escherichia coli with genes for several other components of the translation apparatus. Only three nucleotides separate the termination codon of thrS from the initiation codon of infC. This implies that infC is either cotranscribed with thrS from a thrS promoter or that the transcriptional signals for infC are embedded within the upstream thrS coding region. In the present work, several plasmids have been constructed which encompass infC and various amounts of the upstream thrS sequence. The ability of the plasmid DNA, or derived restriction fragments, to direct the synthesis of initiation factor 3 was tested in an in vitro DNA-dependent coupled transcription-translation system and in plasmid-transformed maxicells. The results indicate that initiation factor 3 is synthesized in the absence of the thrS promoter. A promoter whose presence is sufficient for the expression of infC has been localized to an 89-base-pair region which lies 178 to 267 base pairs upstream of the infC initiation codon. S1 nuclease mapping of in vivo transcripts confirms that a transcription initiation site is located in this region. These studies demonstrate that infC can be transcribed from a promoter within the upstream thrS coding sequence.

Psychophysiological and psychometric studies after manipulating the GABA system by vigabatrin, a GABA-transaminase inhibitor

This study is concerned with the alterations in central and peripheral psychophysiological measures and psychometric variables after experimental manipulation of the most important inhibitory transmitter system of the CNS, the gamma-aminobutyric acid (GABA) system. Vigabatrin (GVG), a new enzyme-activated, irreversible inhibitor of GABA transaminase, which increases cerebrospinal fluid concentrations of GABA and other substrates of GABA transaminase, was given in single oral doses of 1 g, 2 g and 3 g to 10 normal healthy volunteers. In this double-blind, placebo-controlled crossover study, 3 mg lorazepam was given as reference compound. Blood sampling for vigabatrin kinetics, EEG recordings and evaluation of pulse, blood pressure and side effects were carried out at the hours 0, 1, 2, 4, 6, 8 and 24, and psychometric tests at the same times (except the first hour). Pharmacokinetic analyses demonstrated good absorption of GVG with peak plasma concentrations found within the first two hours, dose-dependent areas under the plasma concentration-time curves and about 65% recovery in the 24-h urine. Computer-assisted spectral analysis of the EEG suggested that GVG produces only small changes in the normal CNS, characterized by an augmentation of total power, absolute and relative power of the beta activity and acceleration of the centroid of the total activity. There was also a trend towards an increase of alpha activity and of the absolute and relative power of the dominant frequency, decrease in the alpha centroid and increase of the centroid of the combined delta and theta activity. Lorazepam 3 mg, in contrast, produced highly significant changes characterized by a decrease of total power, alpha activity, absolute and relative power of the dominant frequency and centroid of the combined delta and theta activity, while beta activity as well as the centroid of the alpha, beta and total activity increased. In the resting condition an additional augmentation of slow activity suggested hypnotic properties of 3 mg lorazepam. The latter changes are typical for anxiolytic sedatives and were also reflected at the behavioral level where psychometric data demonstrated a deterioration in the noo- and thymopsychic parameters and sedative effects in psychophysiological variables. GVG, on the other hand, produced only subtle changes characterized by an improvement of noo- and thymopsychic variables and vegetative activation.