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Yttria Stabilised Zirconia (YSZ) is a tough, phase-transforming ceramic that finds use in a wide range of commercial applications from dental prostheses to thermal barrier coatings. Micromechanical modelling of phase transformation can deliver reliable predictions in terms of the influence of temperature and stress. However, models must rely on the accurate knowledge of single crystal elastic stiffness constants. Some techniques for elastic stiffness determination are well-established. The most popular of these involve exploiting frequency shifts and phase velocities of acoustic waves. However, the application of these techniques to YSZ can be problematic due to the micro-twinning observed in larger crystals. Here, we propose an alternative approach based on selective elastic strain sampling (e.g., by diffraction) of grain ensembles sharing certain orientation, and the prediction of the same quantities by polycrystalline modelling, for example, the Reuss or Voigt average. The inverse problem arises consisting of adjusting the single crystal stiffness matrix to match the polycrystal predictions to observations. In the present model-matching study, we sought to determine the single crystal stiffness matrix of tetragonal YSZ using the results of timeof- flight neutron diffraction obtained from an in situ compression experiment and Finite Element modelling of the deformation of polycrystalline tetragonal YSZ. The best match between the model predictions and observations was obtained for the optimized stiffness values of C11=451, C33=302, C44=39, C66=82, C12=240, and C13=50 (units: GPa). Considering the significant amount of scatter in the published literature data, our result appears reasonably consistent. [ABSTRACT FROM AUTHOR]

We present a comprehensive study of free-charge carrier and structural properties of two sets of InN films grown by molecular beam epitaxy and systematically doped with Mg from 1.0×1018 cm-3 to 3.9×1021 cm-3. The free electron and hole concentration, mobility, and plasmon broadening parameters are determined by infrared spectroscopic ellipsometry. The lattice parameters, microstructure, and surface morphology are determined by high-resolution X-ray diffraction and atomic force microscopy. Consistent results on the free-charge carrier type are found in the two sets of InN films and it is inferred that p-type conductivity could be achieved for 1.0×1018 cm-3≲[Mg]≲9.0×1019 cm-3. The systematic change of free-charge carrier properties with Mg concentration is discussed in relation to the evolution of extended defect density and growth mode. A comparison between the structural characteristics and free electron concentrations in the films provides insights in the role of extended and point defects for the n-type conductivity in InN. It further allows to suggest pathways for achieving compensated InN material with relatively high electron mobility and low defect densities. The critical values of Mg concentration for which polarity inversion and formation of zinc-blende InN occurred are determined. Finally, the effect of Mg doping on the lattice parameters is established and different contributions to the strain in the films are discussed. [ABSTRACT FROM AUTHOR]

We have studied hydrogen impurities and related structural properties in state-of-the-art wurtzite InN films with polar, nonpolar, and semipolar surface orientations. The effects of thermal annealing and chemical treatment on the incorporation and stability of H are also discussed. The near-surface and bulk hydrogen concentrations in the as-grown films increase when changing the surface orientation from (0001) to ([formula]) to ([formula]) and to ([formula]), which may be associated with a decrease in the grain size and change of the growth mode from 2D to 3D. Thermal annealing at 350oC in N2 leads to a reduction of H concentrations and the intrinsic levels of bulk H are found to correlate with the structural quality and defects in the annealed films. [ABSTRACT FROM AUTHOR]

We present a detailed study of the structural characteristics of molecular beam epitaxy grown nonpolar InN films with a- and m-plane surface orientations on r-plane sapphire and (100) γ-LiAlO2, respectively, and semipolar (1011) InN grown on r-plane sapphire. The on-axis rocking curve (RC) widths were found to exhibit anisotropic dependence on the azimuth angle with minima at InN [0001] for the a-plane films, and maxima at InN [0001] for the m-plane and semipolar films. The different contributions to the RC broadening are analyzed and discussed. The finite size of the crystallites and extended defects are suggested to be the dominant factors determining the RC anisotropy in a-plane InN, while surface roughness and curvature could not play a major role. Furthermore, strategy to reduce the anisotropy and magnitude of the tilt and minimize defect densities in a-plane InN films is suggested. In contrast to the nonpolar films, the semipolar InN was found to contain two domains nucleating on zinc-blende InN(111)A and InN(111)B faces. These two wurtzite domains develop with different growth rates, which was suggested to be a consequence of their different polarity. Both, a- and m-plane InN films have basal stacking fault densities similar or even lower compared to nonpolar InN grown on free-standing GaN substrates, indicating good prospects of heteroepitaxy on foreign substrates for the growth of InN-based devices. [ABSTRACT FROM AUTHOR]

The lattice parameters and strain evolution in Al1-xInxN films with 0.07≤x≤0.22 grown on GaN-buffered sapphire substrates by metal organic vapor phase epitaxy have been studied by reciprocal space mapping. Decoupling of compositional effects on the strain determination was accomplished by measuring the In contents in the films both by Rutherford backscattering spectrometry (RBS) and x-ray diffraction (XRD). Differences between XRD and RBS In contents are discussed in terms of compositions and biaxial strain in the films. It is suggested that strain plays an important role for the observed deviation from Vegard’s rule in the case of pseudomorphic films. On the other hand, a good agreement between the In contents determined by XRD and RBS is found for Al1-xInxN films with low degree of strain or partially relaxed, suggesting applicability of Vegard’s rule in the narrow compositional range around the lattice matching to GaN. [ABSTRACT FROM AUTHOR]

Only double-outlet right ventricle and pulmonary artery stenosis were diagnosed on prenatal ultrasound. Double-outlet right ventricle and pulmonary artery stenosis were diagnosed on prenatal ultrasound. Congenital heart disease (CHD) is the most common birth defect in newborns, with an incidence of 4.0-6.0% in China. [Extracted from the article]

OBJECTIVE: To discover the impact of the various degrees of coronary artery stenosis (CAD) on the left ventricular systolic dysfunction in steady state with quantitative analysis of the regional systolic myocardium in longitudinal, radial and circumferential direction in patients with coronary artery disease by two-dimensional speckle tracking imaging (STI). PATIENTS AND METHODS: Forty-three normal wall motion-multi vessel coronary artery disease (NWM-MVD) patients labeled as the experimental groups and forty-two subjects with little risk of CAD marked as the control group were enrolled in this study. The two-dimensional STI was obtained in the apical long axis and three levels of the short axis of the left ventricle. The left ventricular wall was divided into 18 segments. The affected myocardia were divided into three groups: group B (coronary stenosis degree ≤50%), group C (coronary stenosis degree 50%-99%)and group D (coronary stenosis degree ≥99%). Using the Q-analysis software, the longitudinal, radial and circumferential systolic strain (SL, SR, SC) and strain ratio (SrL, SrR, SrC) of the myocardium were analyzed. RESULTS: The bradycardia in the NWM-MVD group is greater than that in the control group (16/43 vs. 7/42, p <0.05). Compared with the control group, the SL and SR of group B, group C and group D decreased significantly (p <0.05). Compared with group C, the SL of group D also decreased significantly (p <0.05). However, there was no SC difference among the four groups. Meanwhile, compared with group A, the SrL, SrR and SrC of group B, group C and group D decreased significantly (p <0.05). Compared with group A, group B and group C, the SrL and SrC of group D also decreased (p <0.05). Compared with group A and group C, the SrR of group D decreased. The SrL was equal to 1.085 for the cut-off value, and the sum (1.348) of sensitivity (0.673) and specificity (0.675) were the greatest. Bland-Altman analysis showed that there was myocardium conformity of in both the multi-vessel CAD patients and the control subjects. CONCLUSIONS: Myocardial systolic function was impaired in the MVD patients of group B (coronary stenosis degree ≤50%), group C (coronary stenosis degree 50%-99%)and group D (coronary stenosis degree ≥99%), especially the longitudinal and radial systolic function, even though they had normal wall motion. The SrL equaled 1.085 for the cut-off value, and the sums (1.348) of sensitivity (0.673) and specificity (0.675) were the greatest. Bradycardia might be a compensatory mechanism in NWM-MVD patients. [ABSTRACT FROM AUTHOR]

OBJECTIVE: To evaluate the clinical value of two-dimensional speckle tracking echocardiography for analyzing the left ventricular systolic function in patients with multivessel coronary artery disease with normal wall motion (NWM-MVD). PATIENTS AND METHODS: Forty-five NWMMVD patients and thirty-six subjects with low risk of coronary artery disease (control group) were enrolled in this study. Echocardiogram images of the short axis of the left ventricle and apical long axis were obtained. The Q-analysis software was used to analyze the peak systolic strain of the left ventricular segments and the global longitudinal strain (GLS). We calculated the left ventricular global circumferential strain (GCS) and the radial strain (GRS), as well as the longitudinal, radial and circumferential strain of the basal (Bas-GLS, Bas-GCS, Bas-GRS), middle (Mid-GLS, Mid-GCS, Mid-GRS) and apical segments (Ap-GLS, Ap-GCS, Ap-GRS). RESULTS: (1) The coronary occlusion or subtotal occlusion were visible in 85.71% of the NWM-MVD patients. (2) The heart rate of the NWM-MVD patients was lower than that of the control group [(61.78 ± 6.76) beats/min vs. (66.13 ± 6.24) beats/min, p < 0.05]. The conventional ultrasonic measurement indices are similar between the NWM-MVD group and the control group (p > 0.05). (3) Compared with the control group, the GLS, Bas-GLS, Mid-GLS, Bas- GCS, Mid-GCS, GRS and Bas-GRS were lower in the NWM-MVD group (p < 0.05). CONCLUSIONS: The longitudinal, circumferential and radial systolic functions of the NWMMVD patients were impaired at different degrees. [ABSTRACT FROM AUTHOR]

We develop and discuss appropriate methods based on x-ray diffraction and generalized infrared spectroscopic ellipsometry to identify wurtizte and zinc-blende polymorphs, and quantify their volume fractions in mixed-phase epitaxial films taking InN as an example. The spectral signatures occurring in the azimuth polarization (Muller matrix) maps of mixed-phase epitaxial InN films are discussed and explained in view of polymorphism (zinc-blende versus wurtzite), volume fraction of different polymorphs and their crystallographic orientation, and azimuth angle. A comprehensive study of the structural, phonon and free electron properties of zinc-blende InN films containing inclusions of wurtzite InN is also presented. Thorough analysis on the formation of the zinc-blende and wurtzite phases is given and the structural evolution with film thickness is discussed in detail. The phonon properties of the two phases are determined and discussed together with the determination of the bulk free-charge carrier concentration, and electron accumulation at the mixed-phase InN film surfaces. [ABSTRACT FROM AUTHOR]

We present a theoretical analysis on the applicability of Vegard's linear rule in InxAl-xN alloys in relation to strain related elastic and piezoelectric properties. We derive the elastic stiffness constants and biaxial coefficients, as well as the respective deviations from linearity (Vegard's rule) by using ab initio calculations. The stress-strain relationships to extract composition from the lattice parameters are derived in different coordinate systems for InxAl1-xN with an arbitrary surface orientation. The error made in the composition extracted from the lattice parameters if the deviations from linearity are not taken into account is discussed for different surface orientations, compositions and degrees of strain in the InxAl-xN films. The strain induced piezoelectric polarization is analyzed for InxAl1-xN alloys grown pseudomorphically on GaN. The polarization values are compared with those obtained from our experimental data for the lattice parameters. We establish the importance of the deviation from linearity to correctly determine the piezoelectric polarization and also a smooth, not particular piezoelectric response at GaN lattice matched conditions. [ABSTRACT FROM AUTHOR]

Three-dimensional finite element interlaminar stress solutions of composite laminates with resin layers under uniform axial strain are presented. Their three-dimensional distributions are plotted. In the cross-ply laminate, interlaminar normal and shear stresses are shown to be of free-edge effect. But shear stresses are found to be significantly reduced in the free-edge region, which show some conformity to the boundary stress conditions. In the angle-ply laminate, the stress distributions all vary significantly along both extension and width directions. There exists free-edge effects and end-edge effects in this case; however, the peaky interlaminar stresses are not exactly at the edges, but are near the edge regions. [ABSTRACT FROM PUBLISHER]

We discuss the possibility of determining orientation distribution function (ODF) of cubic phase polycrystals from single exposure Debye-Scherrer diffraction data by a systematic numerical simulation. The fundamental zone of cubic phase crystals is discretised as 5°× 5° × 5° cubic cells, and the aim is to find out those preferred orientations represented by the cells centres which cannot be determined by single exposure Debye-Scherrer diffraction data. Two simulated ODFs corresponding to two different types of linear combination of single preferred orientations are used to validate if the method is suitable for more complicated textures. A data processing routine as well as experimental procedure that enable texture evaluation in metallic cubic phase polycrystals by single exposure high energy monochromatic synchrotron X-ray diffraction with area detector is presented. MTEX is used to estimate ODFs from both single exposure and multi-exposure 2D diffraction patterns. An extruded tungsten wire and a copper cylinder machined from a rolled plate are used to illustrate the whole method. Careful error comparison is made between the ODFs obtained from single exposure and multi-exposure data. Besides, all the diffraction patterns are processed by MAUD to provide a comparison to the MTEX approach, and good agreement is seen between ODFs produced by MAUD and MTEX. [ABSTRACT FROM AUTHOR]

The lattice parameters of InxAl1-xN in the whole compositional range are studied using first-principle calculations. Deviations from Vegard’s rule are obtained via the bowing parameters, δa=0.0412±0.0039 Å and δc=-0.060±0.010 Å, which largely differ from previously reported values. Implications of the observed deviations from Vegard’s rule on the In content extracted from x-ray diffraction are discussed. We also combine these results with x-ray diffraction and Raman scattering studies on InxAl1-xN nanocolumns with 0.627<=x<=1 and determine the E2 phonon frequencies versus In composition in the scarcely studied In-rich compositional range. [ABSTRACT FROM AUTHOR]

Background: Orexin A, a small-molecule peptide, can regulate female hormones, but limited evidence for its mechanism of activity exists in ovine., Aims: The objective of this study was to investigate the effect of orexin A on progesterone (P4) secretion in cultured granulosa of sheep follicles., Methods: Sheep ovarian granulosa were isolated and identified, pre-incubated with luteinizing hormone (LH) (2.5 IU/ml), follicle-stimulating hormone (FSH) (2.5 IU/ml), or oestrogen (1 µg/ml); and cultured in vitro . The pretreated sheep ovarian granulosa were subsequently cultured with different concentrations (1 nM, 10 nM, 58 nM, 100 nM, and 145 nM) of orexin A for varying amounts of time (0 h, 24 h, 48 h, and 72 h). Then, the expression levels of P4, steroidogenic acute regulatory protein (StAR), 3β-Hydroxysteroid dehydrogenase (3β-HSD) and cytochrome P450 (CYP11) were determined., Results: The results showed that the sheep ovarian granulosa were correctly identified. The different concentrations of orexin A promoted the secretion of P4 from granulosa in the ovine ovary compared with that in the control. The expression of StAR, 3β-HSD and P450 (CYP11) gradually increased, and then decreased with increasing concentrations of orexin A, but the expression of P450 (CYP11) decreased with the increase of time., Conclusion: These results revealed that orexin A promotes the secretion of P4 by regulating the expression of StAR, 3β-HSD, and P450 (CYP11). Understanding the mechanism underlying the promotion of P4 by orexin A could open new therapeutic possibilities in the treatment of hormone homeostasis.

Despite the strong interest in optoelectronic devices working in the deep ultraviolet range, no suitable low cost, large-area, high-quality AlN substrates have been available up to now. The aim of this work is the selective area growth of AlN nanocolumns by plasma assisted molecular beam epitaxy on polar (0001) and semi-polar (11-22) GaN/sapphire templates. The resulting AlN nanocolumns are vertically oriented with semi-polar {1-103} top facets when grown on (0001) GaN/sapphire, or oriented at 58° from the template normal and exposing {1-100} non-polar top facets when growing on (11-22) GaN/sapphire, in both cases reaching filling factors ≥80%. In these kinds of arrays each nanostructure could function as a building block for an individual nano-device or, due to the large filling factor values, the overall array top surfaces could be seen as a quasi (semi-polar or non-polar) AlN pseudo-template.

In this paper, a novel (Hydroxyapatite+β-tricalcium phosphate)/Mg-5Sn ((HA+β-TCP)/Mg-5Sn) composite with interpenetrating networks was fabricated by infiltrating Mg-5Sn alloy into porous HA+β-TCP using suction casting technique. The structure, mechanical property and corrosion behaviors of the composite have been evaluated by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), mechanical testing, electrochemical and immersion test. It is shown that the molten Mg-5Sn alloy has infiltrated not only into the pores but also into the struts of the HA+β-TCP scaffold to forming a compact composite. The microstructure observation also shows that the Mg alloy contacts to the HA+β-TCP closely, and no reaction layer can be found between Mg-5Sn alloy and scaffold. The ultimate compressive strength of the composite is as high as 176MPa, which is about four fifths of the strength of the Mg-5Sn bulk alloy. The electrochemical and immersion tests indicate that the corrosion resistance of the composite is better than that of the Mg-5Sn bulk alloy. The corrosion products on the composite surface are mainly Mg(OH)2, Ca3(PO4)2 and HA. Appropriate mechanical and corrosion properties of the (HA+β-TCP)/Mg-5Sn composite indicate its possibility for new bone tissue implant materials., (Copyright © 2015 Elsevier B.V. All rights reserved.)

The objectives of this study were to determine true phosphorus (P) digestibility, degradability of phytate-P complex and the endogenous P outputs associated with brown rice feeding in weanling pigs by using the simple linear regression analysis technique. Six barrows with an average initial body weight of 12.5 kg were fitted with a T-cannula and fed six diets according to a 6 × 6 Latin-square design. Six maize starch-based diets, containing six levels of P at 0.80, 1.36, 1.93, 2.49, 3.04, and 3.61 g/kg per kg dry-matter (DM) intake (DMI), were formulated with brown rice. Each experimental period lasted 10 days. After a 7-day adaptation, all faecal samples were collected on days 8 and 9. Ileal digesta samples were collected for a total of 24 h on day 10. The apparent ileal and faecal P digestibility values of brown rice were affected ( P < 0.01) by the P contents in the assay diets. The apparent ileal and faecal P digestibility values increased from - 48.0 to 36.7% and from - 35.6 to 40.0%, respectively, as P content increased from 0.80 to 3.61 g/kg DMI. Linear relationships ( P < 0.05), expressed as g/kg DMI, between the apparent ileal and faecal digestible P and dietary levels of P, suggested that true P digestibility and the endogenous P outputs associated with brown rice feeding could be determined by using the simple regression analysis technique. There were no differences ( P>0.05) in true P digestibility values (57.7 ± 5.4 v. 58.2 ± 5.9%), phytate P degradability (76.4 ± 6.7 v. 79.0 ± 4.4%) and the endogenous P outputs (0.812 ± 0..096 v. 0.725 ± 0.083 g/kg DMI) between the ileal and the faecal levels. The endogenous faecal P output represented 14 and 25% of the National Research Council (1998) recommended daily total and available P requirements in the weanling pig, respectively. About 58% of the total P in brown rice could be digested and absorbed by the weanling pig. Our results suggest that the large intestine of the weanling pigs does not play a significant role in the digestion of P in brown rice. Diet formulation on the basis of total or apparent P digestibility with brown rice may lead to P overfeeding and excessive P excretion in pigs.

An analytical methodology was developed to quantitate the intracellular nucleotides including mono-, di-, and triphosphates and the diphosphocholine derivative of (-)-2', 3'-deoxy-3'-thiacytidine (3TC) in human peripheral blood mononuclear cells (PBMCs). The procedure includes the resolution of 3TC nucleotides by solid-phase extraction (SPE) on an anion-exchange cartridge, with subsequent enzyme digestion of the resulting phosphates to the parent drug that is ultimately quantitated by high-performance liquid chromatography with UV detection (HPLC-UV). Validation was performed with PBMCs from healthy donors exposed to [3H]3TC, leading to the formation of intracellular nucleotides that were quantitated by anion-exchange HPLC with radioactive detection (HPLC-RA). These nucleotide levels served as reference values and were used for cross-validation with data obtained by HPLC-UV. An excellent correlation was established between the results obtained by HPLC-RA and those obtained by HPLC-UV, with a slope of the regression lines close to unity and intercepts near nullity as well as a correlation coefficient close to unity for all 3TC phosphates. The assay was characterized by a limit of quantitation below 1 ng (amount on column) with a precision (percentage of coefficient of variation of repeated measurement) ranging from 0.8 to 18.1% and an accuracy (deviation of the amount determined by HPLC-UV from the nominal reference value) varying from -14.8 to 19.4%. This methodology was successfully applied to determine the quantity of 3TC nucleotides in PBMCs of a patient infected with human immunodeficiency virus after oral administration of 3TC and stavudine.

AZT-P-ddI is an antiviral heterodimer composed of one molecule of 3'-azido-3'-deoxythymidine (AZT) and one molecule of 2',3'-dideoxyinosine (ddI) linked through their 5' positions by a phosphate bond. The metabolic fate of the dimer was studied with isolated rat, monkey, and human hepatocytes and was compared with that of its component monomers AZT and ddI. Upon incubation of double-labeled [14C]AZT-P-[3H]ddI in freshly isolated rat hepatocytes in suspension at a final concentration of 10 microM, the dimer was taken up intact by cells and then rapidly cleaved to AZT, AZT monophosphate, ddI, and ddI monophosphate. AZT and ddI so formed were then subject to their respective catabolisms. High-performance liquid chromatography analyses of the extracellular medium and cell extracts revealed the presence of unchanged dimer, AZT, 3'-azido-3'-deoxy-5'-beta-D-glucopyranosylthymidine (GAZT), 3'-amino-3'-deoxythymidine (AMT), ddI, and a previously unrecognized derivative of the dideoxyribose moiety of ddI, designated ddI-M. Trace extracellular but substantial intracellular levels of the glucuronide derivative of AMT (3'-amino-3'-deoxy-5'-beta-D-glucopyranosylthymidine [GAMT]) were also detected. Moreover, the extent of the formation of AMT, GAZT, and ddI-M from the dimer was markedly lower than that with AZT and ddI alone by the hepatocytes. With hepatocytes in primary culture obtained from rat, monkey, and human, large interspecies variations in the metabolism of AZT-P-ddI were observed. While GAZT and ddI-M, metabolites of AZT and ddI, respectively, as well as AZT 5'-monophosphate (MP) and ddI-MP were detected in the extracellular media of all species, AMT and GAMT were produced only by rat and monkey hepatocytes. No such metabolites were formed by human hepatocytes. The metabolic fate of the dimer by human hepatocytes was consistent with in vivo data recently obtained from human immunodeficiency virus-infected patients.

The effects of several anti-human immunodeficiency virus nucleoside analogs were examined on neurite regeneration and mitochondrial DNA (mtDNA) synthesis in nerve growth factor-primed PC-12 cells. Under pharmacologically relevant concentrations, the exposure of cells to 2',3'-dideoxyinosine (ddI), 2',3'-dideoxycytidine (ddC) and 2',3'-didehydro-3'-deoxythymidine (d4T) led to a marked dose-dependent inhibition of neurite regeneration with a 50% inhibitory concentration approximating 1, 5 and 15 microM, respectively. In contrast, 3'-azido-3'-deoxythymidine (AZT) and beta-L-2',3'-dideoxy-3'-thiacytidine (3TC) had no effect on neurite regeneration. Inhibition of mtDNA synthesis by ddI was dose dependent, and ddC at a concentration of 10 microM strongly reduced mtDNA content by >75%. However, no inhibition of mtDNA synthesis was detected in cells exposed to 10 microM 3TC or d4T and to 25 microM AZT, suggesting a lack of definite correlation between mtDNA depletion and blockage of neurite regeneration. High performance liquid chromatographic analysis demonstrated that AZT, ddC, 3TC and d4T were anabolized to their respective monophosphate, diphosphate and triphosphate derivatives in the PC-12 cells. In addition, d4T was phosphorylated to form its monophosphate, diphosphate and triphosphate derivatives in isolated mitochondria, whereas ddC was metabolized only to its monophosphate form and no phosphorylated metabolites of 3TC were detected under the same conditions. In summary, the peripheral neuropathy induced by ddC and ddI in patients with acquired immune deficiency syndrome may be accounted for by the depletion of mtDNA content in the neurons. As for d4T, some other mechanism(s) may be involved in its clinical neurotoxicity. Both AZT and 3TC lacked any substantial toxicity in our in vitro model, which is in agreement with the clinical action of these drugs.

beta-D-Uridine protected human granulocyte-macrophage lineage cells in both semi-solid (granulocyte-macrophage colony-forming units, CFU-GM) and liquid cultures against the toxic effects of 3'-azido-3'-deoxythymidine (AZT), 3'-fluoro-3'-deoxythymidine (FLT) and a combination of AZT and FLT, without impairment of the activities of these respective drugs against human immunodeficiency virus (HIV) replication. In addition, beta-D-uridine also protected human CFU-GM against toxicity of the in vivo AZT metabolite, 3'-amino-3'-deoxythymidine (AMT). Beta-L-uridine and alpha-D-uridine, two stereoisomers of the natural form, and the base uracil, were unable to protect cells against either AZT or FLT toxicity, whereas beta-D-uridine-5'-bis(SATE)phosphotriester, a prodrug of beta-D-uridine-5'-monophosphate, successfully protected cells against AZT toxic effects, suggesting that beta-D-uridine needs to be metabolized to its nucleotides to exert a pharmacological effect. These data suggest in addition that AZT, FLT and AMT share a common target site(s) of toxicity involved in myelosuppression.

Long-term therapy of AIDS patients with 3'-azido-3'-deoxythymidine (AZT) remains of concern because of resulting hematopoietic toxicity. While the mechanism(s) of this toxicity remains elusive, alternative strategies are being developed to reduce these toxic effects, including combination therapy with nonmyelotoxic antihuman immunodeficiency virus drugs and/or administration of protective or rescue agents, including cytokines and growth factors. By using a particularly relevant human CD34+ liquid culture system, the unique profiles of dideoxynucleoside (ddN) toxicities to both proliferation and differentiation were demonstrated, with decreased potencies in the order of 3'-fluoro-3'-deoxythymidine (FLT) = 3'-amino-3'-deoxythymidine (AMT) = 2',3'-dideoxycytidine > AZT for inhibition of proliferation and in the order of FLT = AMT > AZT >> 2',3'-dideoxycytidine for inhibition of hemoglobin synthesis. Hemin selectively protected erythroid-lineage human burst-forming unit-erythroid cells from AZT- and AMT-induced inhibition but had no effect on FLT toxicity under similar conditions. Myeloid-lineage human CFU-granulocyte-macrophages were also not protected by hemin against all three ddN analogs. The simultaneous exposure of cells to hemin and AZT resulted in a complete protection of both cell proliferation and hemoglobin synthesis. In contrast, in reversal studies only the inhibition of the percentage of hemoglobin-synthesizing cells returned to control levels, but the inhibition of proliferation of cells previously exposed to AZT was not reversed by hemin. These studies further define the unique and multifactorial mechanism(s) of ddN-induced toxic effects during hematopoietic development of pluripotent stem cells and suggest that the use of hemin could be beneficial in alleviating the toxicity of certain ddN analogs.

The effects of racemic cis-2',3'-dideoxy-3'-thiacytidine [(+/-)-BCH-189] and its two enantiomers on human myeloid and erythroid colony-forming cells were studied by clonogenic assays. The (+)-isomer was the most toxic with a median inhibitory concentration approximating 2 microM in both cell lineages. In contrast, concentrations of the (-)-isomer required for 50% inhibition of granulocyte macrophage colony-forming units (CFU-GM) and erythroid burst-forming units (BFU-E) were 33.9 +/- 15.1 and 169.4 +/- 87.9 microM, respectively. The racemic BCH-189 was quite toxic to these cells, but to a lesser extent than observed with 3'-azido-3'-deoxythymidine and 3'-fluoro-3'-deoxythymidine (positive controls).

3'-Azido-2',3'-dideoxyuridine (AzddU, CS-87) is a potent inhibitor of human immunodeficiency virus replication in vitro with low bone marrow toxicity. Although AzddU is currently being evaluated in clinical trials, its catabolic disposition is unknown. Pharmacokinetic studies in rhesus monkeys have demonstrated that a 5'-O-glucuronide is excreted in urine. The present study examined the catabolic disposition of AzddU is isolated rat hepatocytes, a model for the study at the cellular level of biosynthetic, catabolic and transport phenomena in the liver. Following exposure of cells to 10 microM [3H]AzddU, low intracellular levels of two catabolites, identified as 3'-azido-2',3'-dideoxy-5'-beta-D-glucopyranosyluridine (GAzddU) and 3'-amino-2',3'-dideoxyuridine (AMddU), were detected. Studies using rat microsomes demonstrated that GAzddU formation was only detected in the presence of uridine 5'-diphosphoglucuronic acid, and that the rate of AMddU formation increased significantly in the presence of NADPH. Under similar conditions, reduction of the 3'-azido function was also demonstrated herein with 3'-azido-2',3'-dideoxycytidine (AzddC), 3'-azido-2',3'-dideoxy-5-methylcytidine (AzddMeC) and 3'-azido-2',3'-dideoxyguanine (AzddG), suggesting that enzymatic reduction to a 3'-amino derivative is a general catabolic pathway of 3'-azido-2',3'-dideoxynucleosides at the hepatic site.

Metabolic studies in humans have demonstrated that 3'-azido-3'-deoxythymidine (AZT) is primarily eliminated as its 5'-O-glucuronide (GAZT). However, no detailed cellular metabolic studies have been reported on the complete catabolic fate of AZT at the hepatic site. Because the liver is probably the major site of AZT catabolism, the metabolism and transmembrane distribution of AZT were evaluated in freshly isolated rat hepatocytes, a model for the study at the cellular level of biosynthetic, catabolic, and transport phenomena in the liver. Following exposure of cells to 10 microM [3H]AZT, the predominant intracellular catabolite was GAZT, which reached a concentration of approximately 22 microM by 60 min. Additionally, under nonreducing conditions substantial levels of two previously unidentified AZT catabolites that were formed at the hepatic site and were distinct from any known anabolites or catabolites were also detected. These catabolites were identified as 3'-amino-3'-deoxythymidine (AMT) by fast atom bombardment mass spectrometry and 3'-amino-3'-deoxythymidine glucuronide (GAMT) through specific enzymatic hydrolysis. However, AMT was not a substrate for uridine 5'-diphosphoglucuronyltransferase and GAMT was found to be a reductive product of GAZT. Studies using rat and human liver microsomes demonstrated that the rate of formation of AMT and GAMT increased in the presence of NADPH, suggesting the involvement of a NADPH-dependent enzyme system. Studies using human hematopoietic progenitor cells demonstrated that AMT was 5- to 7-fold more toxic to human colony-forming units granulocyte-macrophage and burst-forming units erythroid than was AZT. This study provides the first detailed catabolic profile of AZT at the hepatic site and emphasizes the critical role that the liver plays in drug clearance. Formation of AMT, a highly toxic catabolite of AZT, raises a question regarding the role of AMT in the cytotoxic effects of AZT observed in patients.

C-1027-AG, a selective antagonist of antitumor antibiotic C-1027, was isolated by column chromatography on DEAE-cellulose, butyl-Toyopearl and Sephadex G-50 from a culture filtrate of Streptomyces globisporus. The amino acid sequence of purified C-1027-AG was determined with a protein sequencer on the basis of fragment peptides obtained by enzymatic hydrolysis with lysylendopeptidase, V8 protease, endopeptidase AspN and chymotrypsin, after performic acid oxidation. C-1027-AG is shown to consist of a single polypeptide chain cross-linked by two disulfide bonds, and to contain a total of 110 amino acid residues with alanine and glycine as its amino- and carboxyl-termini, respectively; its molecular weight was calculated to be 10,500 daltons. The primary structure of C-1027-AG is indicated to be identical to the protein moiety of C-1027, and is highly homologous to the sequences of antitumor proteins obtained from other Streptomyces species.

The relative antiviral potencies of five nucleotide heterodimers of 3'-azido-3'-deoxythymidine (AZT), 3'-azido-3'-deoxythymidilyl-(5',5')-2'-3'-dideoxy-5'-adenylic acid (AZT-P-ddA), 3'-azido-3'-deoxythymidilyl-(5',5')-2',3'-dideoxy-5'-inosinic acid (AZT-P-ddI), and the corresponding 2-cyanoethyl congeners AZT-P(CyE)-ddA and AZT-P(CyE)-ddI, were determined in primary human peripheral blood mononuclear cells infected with human immunodeficiency virus type 1. The homodimer 3'-azido-3'-deoxythymidilyl-(5',5')-3'-azido-3'-deoxythymidilic acid (AZT-P-AZT) was also included for comparison. The potencies of the compounds were AZT-P-ddA greater than or equal to AZT-P-ddI greater than AZT-P(CyE)-ddA greater than or equal to AZT-P(CyE)-ddI greater than or equal to AZT greater than AZT-P-AZT. Whereas AZT-P-ddA and AZT-P-ddI had in vitro therapeutic indices greater than that of AZT, the homodimer of AZT had a low therapeutic index. AZT-P-ddI exhibited the lowest toxicity in peripheral blood mononuclear, Vero, or CEM cells. Combination studies between AZT and 2',3'-dideoxyinosine (ddI) at nontoxic concentrations indicated a synergistic interaction at a drug ratio of 1:100. At higher ratios (1:500 and 1:1,000), the interactions were synergistic only at concentrations that produced up to 75% virus inhibition. At higher levels of antiviral effects, this combination was antagonistic, as determined by the multiple drug effect analysis method. AZT-P-ddI was about 10-fold less toxic than AZT to human granulocyte-macrophage progenitor cells. However, no significant difference was apparent when the compounds were evaluated against cells of the erythroid lineage. The greater antiviral activity and lower toxicity of this compound could not be attributed to the extracellular decomposition of the dimer in media at physiological temperature and pH. However, in acidic solutions, AZT-P-ddI decomposed in a pH-dependent manner. Advanced preclinical studies with this heterodimer of two clinically effective antiretroviral agents should be considered.

The new antibiotics 4181-A and B were isolated from the fermentation broth of Streptomyces griseus, a soil isolate. Their molecular formulae were determined as C29H21NO9 and C28H19NO9, respectively. The UV, IR and NMR spectra suggest that they possess a quinone moiety in their structures. They were found to have antibacterial, antifungal and antitumor activity.

A new macromolecular antibiotic C-1027 was obtained from the broth filtrate of Streptomyces globisporus C-1027 by precipitation with ammonium sulfate, DEAE-cellulose column chromatography and gel filtration chromatography on a Sephadex G-75 column. This antibiotic, prepared as a white powder, is an acidic polypeptide having an isoelectric point of pH 3.5-3.7 and a molecular weight of 15,000 as determined by SDS-polyacrylamide gel electrophoresis and gel filtration chromatography. The acid hydrolysate of the purified antibiotic C-1027 contained no methionine or tryptophan. From the physico-chemical data, it may be considered to possess a very labile non-protein chromophore.

Strain C-1027, an actinomycete isolated from a soil sample collected in China, was found to produce the new antibiotic, C-1027. From taxonomical studies on its morphological, cultural and physiological characteristics, this antibiotic-producing strain was identified as Streptomyces globisporus C-1027. Antibiotic C-1027 has antimicrobial activity against most Gram-positive bacteria but not against Mycobacterium sp. or Gram-negative bacteria. This antibiotic shows remarkable activity in spermatogonial assay and potent cytotoxicity against KB carcinoma cells in vitro, and exhibits inhibition on transplantable tumors in mice.