Marginal and conditional approaches to multivariate variables subject to limit of detection

A marginal approach and a variance-component mixed effect model approach (here called a conditional approach) are commonly used to analyze variables that are subject to limit of detection. We examine the theoretical relationship and investigate the numerical performance of these two approaches. We make some recommendations based on our results. The marginal approach is recommended for bivariate normal variables, and the variance-component mixed effect model is preferable for other multivariate analysis in most circumstances. Two approaches are illustrated through one case study from a preclinical experiment.

Asymmetric synthesis of chiral 4-substituted 5,5-diethyl oxazolidin-2-ones as potential effective chiral auxiliaries

Four new chiral 4-substituted 5,5-diethyl oxazolidin-2-ones (5a-5d) as potential effective chiral auxiliaries were synthesized from readily available amino acids via asymmetric etherification, Boc protection, Grignard reaction and cyclization reactions in four steps with overall yields of 50-60%.

A novel gene-samfR involved in early stage of Streptomyces ansochromogenes differentiation

A 4.6 kb DNA fragment was cloned from the DNA library of Streptomyces ansochromogenes using a partial DNA fragment located in the downstream of promoter-P(TH4) as probe. The experiments revealed that this DNA fragment consists of saw D gene and a 1.4 kb Pvu II fragment which can accelerate mycelium formation o fS. ansochromogenes. The nucleotide sequence of 1.4 kb DNA fragment was determined and analysed; the result indicated that the fragment contains one complete open reading frame (ORF) which encodes a protein with 213 amino acids, and this gene was designated as samfR. The deduced protein has 36% amino acid identities and 52% amino acid similarities in comparison with that encoded by hppR gene, which is involved in the regulation of catabolism for 3-(3-hydroxyphenyl) propionate (3HPP) in Rhodococcus globerulus. The function of samfR gene was studied using strategy of gene disruption, and the resulting samfR mutant failed to form aerial hyphae and spores, its development and differentiation stopped at the stage of substrate mycelium in contrast with wild type strain. The results showed that the samfR gene is closely related to S. ansochromogenes differentiation.

Structure and function of sawB, a gene involved in differentiation of Streptomyces ansochromogenes

A partial DNA library of Streptomyces ansochromogenes 7100 was constructed by using plasmid pl J702 as vector and white mutant W19 as recipient. About 3 000 clones were obtained, two of which gave rise to the grey phenotype as wild type 7100. The plasmids were isolated from two transformants. The result indicated that the 5.2 kb and 5.8 kb DNA fragments were inserted into plJ702. The resulting recombinant plasmids were designated as pNL-1 and pNL-2 respectively. The 1.25 kb Pstl I -Apa I DNA fragment from pNL-1 was recognized as its complementarity to W19 strain. The nucleotide sequence of the 3.0 kb Pst I DNA fragment including 1.25 kb was determined and analyzed. The result indicated that this DNA fragment contains one complete open reading frame (ORF1) which encodes a protein with 295 amino acid residues, and this gene was designated as sawB. The deduced protein has 81% amino acid identities in comparison with that encoded by whiH in Streptomyces coelicolor. The function of sawB gene was studied by using strategy of gene disruption, and the resulting sawB mutant failed to form spores and produced loosely coiled aerial hyphal. The result showed that sawB is closely related to hyphal coiling and sporulation in S. ansochromogenes, and also indicated that the sawB can complement whiH mutant (C119) to restore the grey phenotype of Streptomyces coelicolor J 1501 (wild type).

Expression of interferon-gamma in human adrenal gland and kidney tumours

It is known that interferon-γ (IFN-γ) is produced by activated T and NK lymphoid cells, mononuclear cells, and macrophage and dendritic cells. Our previous studies have shown that IFN-γ-like immunoreactivity also appears in human adrenal cortical tumour and phaeochromocytoma. To investigate whether human tumour cells can produce IFN-γ, we examined 429 biopsy specimens of 30 kinds of tumour and tumour-surrounding tissues in adrenal glands and in kidneys by using immunohistochemistry and in situ hybridisation. IFN-γ immunoactivity was shown in 34.3% of the adrenal cortical adenomas, 50% of the adrenal cortical carcinomas, 26.7% of the phaeochromocytomas, 26.7% of the clear cell renal cell carcinomas (RCCs), 22% of the adrenal cortexes and 40% of medullas adjacent to tumours. The positive samples and expression areas were well overlapped between the IFN-γ mRNA and the immunohistochemistry staining. Western blot analysis has further confirmed the immunohistochemistry results by showing a distinct IFN-γ band corresponding to 17.4 kDa in tissue extracts from adrenal cortical adenoma, phaeochromocytoma and clear cell RCCs. These results indicate that IFN-γ is produced by some types of tumour cells, suggesting it may play a dual role in the development of these tumours.

Cloning and characterization of sanO, a gene involved in nikkomycin biosynthesis in Streptomyces ansochromogenes

AIMS

To clone and characterize sanO, a gene involved in the biosynthesis of nikkomycins in Streptomyces ansochromogenes.

METHODS AND RESULTS

A 4.5-kb BamHI-KpnI fragment was cloned and sequenced. Sequence analysis revealed that this fragment contains three complete open reading frames. The largest one with 2034 bp was designated sanO, which encodes a protein consisting of 667 amino acids with high similarity to module of peptide synthetase. sanO disruption mutants produced no nikkomycin X, but formed nikkomycin Z at almost the same level of the wild-type strain. The production of nikkomycin X can be recovered by genetic complementation of sanO disruption mutants. Primer extension also revealed that transcription start point(tsp) of sanO was localized 87 bp upstream of the potential start codon (GTG).

CONCLUSIONS

sanO was essential for the biosynthesis of nikkomycin X.

SIGNIFICANCE AND IMPACT OF THE STUDY

Nikkomycins have received increased interest of study because of their prospective application in agriculture and medicine. Cloning and characterization of genes involved in the nikkomycin biosynthesis will help to elucidate the whole biosynthetic pathway of nikkomycins.

Studies of apoptosis of malignant lymphoma cells induced by arsenic trioxide

The present study investigated the effect of As(2)O(3)on malignant lymphoma cells. Cell apoptosis was detected by cell staining and TdT-mediated dUTP Nick-end Labelling (TUNEL). Cellular DNA and protein expression content were determined by immunohistochemistry and flow cytometry. It was found that 0.5-2.0 microm /l As(2)O(3)could inhibit cell growth, including Raji cells and lymphoma cells from patients, and induce apoptosis, such as condensed chromatin and nuclear fragmentation with intact cell membrane, i.e. apoptotic body. It was also found that the cells of the sub-G(1)phase increased significantly and bcl-2 gene expression was greatly downregulated. However, this effect was not observed for Jurkat cells under the same conditions. We concluded that As(2)O(3)at a range of 0.5-2.0 microm /l can inhibit the growth and induce apoptosis in malignant lymphoma cells, which may have therapeutic potential.

Dual role of p300 in the regulation of p53 stability

While the function of p300 as a transcriptional co-activator of p53 is well documented, its role in the regulation of p53 stability remains ill-defined since opposite effects of p300 on p53 levels have been reported. We show here that p300 stabilizes both p53 and its negative regulator MDM2, thereby enhancing the p53/MDM2 negative regulatory loop. Binding of p300 is associated with the retention of p53 in the nucleus, which results in the accumulation of p53 in an acetylase-independent manner. Stabilization of MDM2, on the other hand, requires the acetylase activity of p300. Importantly, MDM2, once expressed, is able to reverse the stabilizing effect of p300 on p53. A temperature-permissive p53-expressing cell line enabled us to demonstrate the completely opposite roles of p300 in the regulation of p53 stability, depending on the expression of MDM2. Prior to p53 activation, when MDM2 levels are low, p300 acts as a positive regulator to increase p53 levels. Upon shifting to permissive temperature, however, when MDM2 expression is induced, p300 becomes a negative regulator of p53 by stabilizing MDM2 and thereby augmenting MDM2's ability to target p53 for degradation.

Identification of p53 sequence elements that are required for MDM2-mediated nuclear export

It has been demonstrated that MDM2 can differentially regulate subcellular distribution of p53 and its close structural homologue p73. In contrast to MDM2-mediated p53 nuclear export, p73 accumulates in the nucleus as aggregates that colocalize with MDM2. Distinct distribution patterns of p53 and p73 suggest the existence of unique structural elements in the two homologues that determine their MDM2-mediated relocalization in the cell. Using a series of p53/p73 chimeric proteins, we demonstrate that three regions of p53 are involved in the regulation of MDM2-mediated nuclear export. The DNA binding domain (DBD) is involved in the maintenance of a proper conformation that is required for functional activity of the nuclear export sequence (NES) of p53. The extreme C terminus of p53 harbors several lysine residues whose ubiquitination by MDM2 appears to be the initial event in p53 nuclear export, as evidenced by the impaired nucleocytoplasmic shuttling of p53 mutants bearing simultaneous substitutions of lysines 370, 372, 373, 381, 382, and 386 to arginines (6KR) or alanines (6KA). Finally, the region between the DBD and the oligomerization domain of p53, specifically lysine 305, also plays a critical role in fully revealing p53NES. We conclude that MDM2-mediated nuclear export of p53 depends on a series of ubiquitination-induced conformational changes in the p53 molecule that lead to the activation of p53NES. In addition, we demonstrate that the p53NES may be activated without necessarily disrupting the p53 tetramer.

A non-potentiometric sensing method for the determination of pentoxyverine with PQC sensors based on ion-pair complexes

The construction and general performance characteristics of three piezoelectric quartz crystal sensors responsive to the pentoxyverine are described here. This kind of non-potentiometric sensing method is based on use of ion-pair complexes of the pentoxyverine cation with three counter anions, namely, tungstophosphate, tetraphenylborate and picrolonate. The complexes were embedded in a PVC matrix. Adsorption of the pentoxyverine ion on the complex caused a frequency decrease of the crystal. The frequency decrease was proportional to the amount of adsorbed analyte. The influencing factors were investigated in detail, and then optimized. The proposed sensors exhibit reasonable selectivity and a higher sensitivity than the potentiometric sensors. For a sensor modified with pentoxyverine-phosphotungstate, the calibration graph was linear over concentration of 1.0 x 10(-7) - 5.0 x 10(-5) M with a detection limit of 6 x 10(-8) M at pH 5.4.

A facile and effective screening method for p21WAF1 promoter activators from microbial metabolites

We have developed a novel p21WAF1 promoter activator screening system based on rapid and facile luciferase activity assay of a model cell system (H1299/tsp53-luc cells), a stable luciferase expression cell line established by transfecting H1299/tsp53 cells with a reporter gene construct pWWP-Luc-BSD. This plasmid was constructed by subcloning the 2.4 kb p21WAF1 promoter and a 2.6 kb of luciferase cDNA fragment activated by the p21WAF1 promoter into a pMAM2-BSD expression vector containing the blasticidin S deaminase gene (BSD). A BSD-resistant clone H1299/tsp53-luc#4, showing the highest response to p53 activation (by temperature shift from 37 degrees C to 32 degrees C) by luciferase production, was used for screening microbial culture broths. Among approximately 1200 screened samples, trichostatin A related compounds and a new compound, lucilactaene, were isolated. This provides an effective and facile screening system for p21WAF1 promoter activators which should be of considerable value in the rapid identification of new anticancer agents.

Subcellular distribution of p53 and p73 are differentially regulated by MDM2

The binding of MDM2 targets p53, but not p73, for degradation, whereas it suppresses the transactivation function of both proteins. MDM2 also mediates p53 nuclear export, but its role in the regulation of p73 distribution is unknown at the present time. We show here that, in sharp contrast to p53, MDM2 induces p73 to form nuclear aggregates that colocalize with MDM2 but are distinct from the promyelocytic leukemia dots. The MDM2 ring-domain that is necessary for mediating p53 nuclear export is not required for the induction of the p73 nuclear aggregates. Using a domain-swapping approach, we demonstrate that the inability of p73 to nuclear-export is attributable to its nonfunctional nuclear-export sequence.

Use of a quartz crystal impedance technique to monitor the degradation of chondroitin sulfate by hyaluronidase

A new quartz crystal impedance hyaluronidase sensing technique, which is based on the changes in viscosity and density during the enzymatic hydrolysis of chondroitin sulfate (CS) by hyaluronidase (HAse), is established in this paper. The variations of equivalent circuit parameters of the piezoelectric quartz crystal (PQC) during the enzymatic degradation are discussed. The initial hydrolysis rate of CS by HAse is obtained from the changes in viscosity and density with incubation time. Kinetic parameters (the Michaelis constant K(m) and the maximum hydrolysis rate V(max)) of the degradation process are estimated by using a linear method of Lineweaver-Burk plot. K(m) is 2.73 +/- 0.20 mg.ml(-1) and V(max) is -(5.43 +/- 0.38) x 10(-4) kg.m(-2).s(-1/2).min(-1.)

Construction and application of phenytoin anion-selective electrode based on bulk acoustic wave (BAW) sensing technique

This paper describes the construction of an anion-selective bulk acoustic wave (BAW) sensor for the direct determination of phenytoin sodium for the first time. Based on the sensitive mass response of a piezoelectric quartz crystal (PQC) and selective adsorption-desorption across the modified film, the BAW sensor was fabricated by coating a polyvinylchloride (PVC) film containing activator on one side of a PQC. The method was found to be sensitive, rapid and easy to handle without pretreatment of the sample. The logarithm of the frequency shift of the PQC shows a linear relationship to the logarithm of the concentration of phenytoin over the range 6.7 x 10(-8)-8.0 x 10(-4) M with a detection limit of 1.0 x 10(-8) M at pH 10.0. Recoveries were in the range 98.5-102.0%. Influencing factors were examined and optimized. Also discussed is the preliminary application of the phenytoin BAW sensor in serum and injection. The results for real samples obtained by the proposed method agreed with those obtained by conventional methods.

Selective determination of dopamine in the presence of ascorbic acid at an over-oxidized poly(N-acetylaniline) electrode

An over-oxidized poly(N-acetylaniline) (PNAANI)/GCE was used to determine dopamine (DA) in a large excess of ascorbic acid (AA) by differential pulse voltammetry. A linear relation between Ip and DA concentration was found over the range 5.0 x 10(-7) to 2.0 x 10(-5) M. The detection limit was 1.68 x 10(-8) M for S/N = 3 and 400 microM AA did not interfere with the DA determination. The high sensitivity was due to accumulation and selectivity was due to charge discrimination. The mechanism of selective determination of DA at over-oxidized PNAANI/GCE was also proposed.

A piezoelectric biomimetic sensor for aminopyrine with a molecularly imprinted polymer coating

A molecularly imprinted polymer for aminopyrine was synthesized using methacrylic acid as functional monomer. The polymer was employed as the recognition element of a piezoelectric bulk acoustic wave biomimetic sensor for aminopyrine. Influencing factors were investigated in detail and optimized. This sensor exhibited high selectivity and sensitivity to aminopyrine. The response range of the sensor was between 5.0 x 10(-8) and 1.0 x 10(-4) M with a detection limit of 2.5 x 10(-8) M in the aqueous system. Scatchard analysis with UV spectrophotometry showed that the same class of binding sites was formed in the molecularly imprinted polymer in the studied concentration range, and the dissociation constant and the apparent maximum number of these binding sites were estimated to be 2.29 mM and 165.0 mumol g-1 dry polymer, respectively. Impedance analysis was employed to verify the imprinting effect and lack of variation in the viscoelasticity of the polymer coating during detection.

A study of a new TSM bio-mimetic sensor using a molecularly imprinted polymer coating and its application for the determination of nicotine in human serum and urine

A new bio-mimetic quartz crystal thickness-shear-mode (TSM) sensor, using an imprinted polymer coating as the sensitive material, has been fabricated and applied to the determination of nicotine (NIC) in human serum and urine. The molecularly imprinted polymer (MIP) was synthesized using NIC as the template molecule and methacrylic acid (MAA) as the functional monomer. The sensor showed high selectivity and a sensitive response to NIC in aqueous system. The linear response range of the sensor was between 5.0 x 10(-8) and 1.0 x 10(-4) M with a detection limit of 2.5 x 10(-8) M. The viscoelasticity of the coating in the air and in liquid has been studied by the impedance spectrum. The MIP sensor was stable and exhibited effective reproducibility. Satisfactory results were achieved in the detection of the real samples.

[Structure and function of sanL--a gene involved in nikkomycin biosynthesis of Streptomyces ansochromogenes]

The chromosome walking strategy has been used in this experiment and a 10 kb DNA fragment was cloned from the cosmid library of Streptomyces ansochromogenes using a partial DNA fragment involved in the nikkomycin biosynthesis as a probe. The nucleotide sequence showed that the DNA fragment contains two complete open reading frames (ORFs), they are designated as sanK and sanL respectively. The sanL is located on the upstream of sanK, it has 1281 nucleotides with ATG at 345 position as start codon and TGA at 623 position as stop codon. The deduced product is L-lysine 2-aminotransferase using Blastx program. The experiment of gene disruption indicated that this gene is closely related to nikkomycin biosynthesis of Streptomyces ansochromogenes.

Development of a thickness shear mode acoustic sensor based on an electrosynthesized molecularly imprinted polymer using an underivatized amino acid as the template

The preparation and characterization of electrosynthesized poly(o-phenylenediamine) (iPoPD) as a molecular imprinting material were studied by an in situ quartz crystal impedance method. The changes of delta f0, delta R1, delta L1 and delta C0 suggest that the polymer film was compact and rigid. The thickness shear mode (TSM) acoustic sensor modified with this material exhibits molecular recognition ability to the template molecule of DL-phenylalanine. In the range 2-20 mM, a linear relationship between the frequency shift delta f0 and logC was found from the calibration graph. Scatchard analysis of the relevant calibration graph offers information on the equilibrium of the binding interaction and the recognition sites. Using this electropolymerization technology, the preparation of the sensor was very simple and the reproducibility of preparation was very good. In particular, it offers possibilities for sensor miniaturization.