In vitro stability of triclosan in dentifrice under simulated use condition

Triclosan has been formulated into a dentifrice at a 0.3% level to enhance the antibacterial function of the dentifrice, to improve oral health and to decrease the daily malodor inside the mouth cavity. The hypothesis that chloroform may be generated from triclosan when contacted with chlorinated drinking water has challenged our guarantee of safe use of triclosan in oral care products, especially in Colgate Total toothpaste. Currently, there was no available analytical method to detect chloroform levels under the use conditions expected during daily tooth brushing. To fill this gap and to continue guaranteeing that our customers can safely use Colgate Total toothpaste products, a gas chromatography-single ion monitoring-mass spectrometry method for detecting chloroform in artificial saliva media has been developed. The limit of detection (LOD) and limit of quantitation are about 41 and 130 ppb, respectively. This LOD level is lower than the current Environmental Protection Agency trihalomethanes contamination limit, which is required for our daily drink water. Our in vitro study indicated that Colgate Total does not form detectable chloroform levels (41 ppb) over the range of expected consumer-brushing times while using normal chlorinated drinking water.

High quality InAs quantum dots grown on patterned Si with a GaAs buffer layer

Ordered and dense InAs quantum dots grown on patterned Si(100) with a thin GaAs buffer layer have been investigated by transmission electron microscopy and electron energy loss spectroscopy. {111} faceted InAs quantum dots with good crystallinity were observed on top of the underlying GaAs buffer layer. It was revealed that the GaAs buffer layer and the lateral expansion of InAs have played key roles in releasing the misfit strain between InAs and Si and suppressing the formation of lattice defects in InAs quantum dots. These results suggest a possible pathway for the strain relaxation in the formation of quantum dots.

Band structure asymmetry of bilayer graphene revealed by infrared spectroscopy

We report on infrared spectroscopy of bilayer graphene integrated in gated structures. We observe a significant asymmetry in the optical conductivity upon electrostatic doping of electrons and holes. We show that this finding arises from a marked asymmetry between the valence and conduction bands, which is mainly due to the inequivalence of the two sublattices within the graphene layer and the next-nearest-neighbor interlayer coupling. From the conductivity data, the energy difference of the two sublattices and the interlayer coupling energy are directly determined.

Expression of immune response genes in the stifle joint of dogs with oligoarthritis and degenerative cranial cruciate ligament rupture

Dysregulation of immune responses within joints plays an important role in development of inflammatory arthritis. We determined expression of a panel of immune response and matrix turnover genes in synovial fluid collected from a group of dogs with stifle oligoarthritis and associated degenerative cranial cruciate ligament (CCL) rupture (n=27). We also studied synovial fluid gene expression in dogs affected with other forms of degenerative arthritis (n=9) and in the stifle joint of healthy dogs with intact CCL (n=14). After collection, synovial cells were pelleted and RNA was isolated. Relative expression of cathepsin K, cathepsin S, tartrate-resistant acid phosphatase (TRAP), matrix metalloproteinase-9 (MMP-9), invariant chain (li), toll-like receptor-2 (TLR-2), and TLR-9 was determined using real-time quantitative RT-PCR. Data were normalized to peripheral blood mononuclear cells (PBMC) as an internal control. Relative expression of cathepsin K, MMP-9, TRAP, and li was increased in the stifle synovial fluid of dogs with oligoarthritis, when compared with the stifles of healthy dogs (P<0.05). In contrast, relative expression of all of the genes-of-interest in synovial fluid from joints affected with other forms of arthritis was not significantly different from the stifles of healthy dogs. TRAP expression was also significantly increased in the stifle joints of dogs with oligoarthritis, when compared to joint expression of TRAP in dogs with other forms of degenerative arthritis (P<0.05). In the dogs with stifle oligoarthritis, expression of both matrix turnover and immune response genes was increased in stifle synovial fluid, when compared with the internal PBMC control, whereas in healthy dogs and dogs with other forms of arthritis, only expression of matrix turnover genes was increased in synovial fluid, when compared with the internal PBMC control (P<0.05). Taken together, these findings suggest that antigen-specific immune responses within the stifle joint may be involved in the pathogenesis of persistent synovitis and associated joint degradation in dogs with oligoarthritis and degenerative CCL rupture.

Validation of a testis specific serine/threonine kinase [TSSK] family and the substrate of TSSK1 & 2, TSKS, as contraceptive targets

A family of testis specific serine/threonine kinases, TSSK1-4 and SSTK, in addition to the substrate of TSSK1 & 2, TSKS, have been studied during the past several years in our laboratory. This paper will provide a general background on these kinases through review of pertinent literature and then will summarize data from our laboratory germane to evaluating these kinases as candidate targets for future development of small molecule kinase inhibitors that may serve to regulate male fertility. Bio-informatic and structural analyses of human TSSK1-4 and SSTK indicate that these kinases constitute a unique subfamily belonging to the AMPK branch on the human kinome tree. Expression studies showed that all five kinases and the TSKS substrate are testis abundant, if not strictly testis specific, indicating that tissue specific contraceptive targeting is possible. In situ hybridization further confirmed that mouse TSSK2, SSTK and TSKS are post-meiotic in their expression patterns, a finding that makes them possible targets of reversible contraceptive intervention by preserving spermatogonia and spermatocytes. Our laboratory detected TSSK2, TSKS and SSTK proteins in mature spermatozoa for the first time. TSKS was localized to the centrioles of human spermatozoa, while TSSK2 was observed in the sperm neck, equatorial segment and mid-piece of the sperm tail, and SSTK was localized in the equatorial segment. The interaction and binding between human TSSK2 and TSKS was confirmed by several methods: this substrate and enzyme interaction offers a particularly interesting opportunity for drug design. In vitro kinase assay showed phosphorylation of TSKS by TSSK2. The TSKS phosphopeptide, HGLSPATPIQGCSGPPGS*PEEPPR, was identified by IMAC-LC-FTMS, with serine 285 being phosphorylated (representend by asterisk). These results provide a rationale for high-throughput screening of inhibitors for TSKS phosphorylation and further studies of members of this kinase family as targets for both male contraception and intra-vaginal spermicides.

Comparisons between different approximations to energy dissipation rate in a self-preserving far wake

By using a four-hot-wire probe and an eight-hot-wire probe, different approximations to energy dissipation rate have been made in the far field of a cylinder wake. The appropriateness of the various approximations is evaluated by examining their mean values, spectra, conditional analysis, and scaling range exponents. It is found that there are significant differences between the instantaneous values of E(iso), the isotropic dissipation rate, and other approximations. The present measurements also allow the examination of the spatial correlation between the energy dissipation rate and the enstrophy Omega. While the correlation between E(iso) and Omega is low, there is a strong correlation between the other approximations to energy dissipation rate and the enstrophy Omega. The scaling range exponents show that the substitutes to the energy dissipation rate and enstrophy based on isotropy are more intermittent than their corresponding true values. The present results suggest that using E(iso) as a substitute of should be re-examined, especially for the instantaneous values.

Prevalence and risk factor analysis of microalbuminuria in Japanese general population: the Takahata study

Microalbuminuria, an indicator of glomerular injury, is associated with increased risk of progressive renal deterioration, cardiovascular disease, and mortality. However, the prevalence of microalbuminuria in Japanese general population is less certain. Thus, we examined the prevalence of microalbuminuria and its associated risk factors in Japan. Subjects of this cross-sectional study were asymptomatic individuals over 40 years in Takahata, Japan. Urine albumin-creatinine ratio was calculated from a single-spot urine specimen collected in the morning. Creatinine clearance (CCr) was obtained by Cockcroft-Gault equation. Multivariate logistic regression analysis was used to determine which risk factors (i.e., age, hypertension, diabetes, obesity, and salt intake) might predict the presence of microalbuminuria. A total of 2321 subjects (mean age, 64 years; men, 1034; women, 1287) were entered into the final analysis. Among them, the prevalence of microalbuminuria, macroalbuminuria, and proteinuria by dipstick test (> or = 1+) were 317 (13.7%), 39 (1.7%), and 103 (4.4%), respectively. Age, hypertension, and diabetes were independently associated with microalbuminuria in men. In addition to the classical risk factors detected in men, estimated 24-h urinary sodium excretion and uric acid were also independently associated with microalbuminuria in women. Among the 668 subjects with renal insufficiency (CCr <60 ml/min/1.73 m(2)), the prevalence of microalbuminuria and macroalbuminuria were 119 (17.8%) and 18 (2.7%), respectively. In conclusion, microalbuminuria is prevalent across all age groups and is associated with lifestyle-related risk factors in Japanese general population. However, there are a substantial number of subjects with renal insufficiency accompanying no microalbuminuria.

Laser seeding of the storage-ring microbunching instability for high-power coherent terahertz radiation

We report the first observation of laser seeding of the storage-ring microbunching instability. Above a threshold bunch current, the interaction of the beam and its radiation results in a coherent instability, observed as a series of stochastic bursts of coherent synchrotron radiation (CSR) at terahertz frequencies initiated by fluctuations in the beam density. We have observed that this effect can be seeded by imprinting an initial density modulation on the beam by means of laser "slicing." In such a situation, most of the bursts of CSR become synchronous with the pulses of the modulating laser and their average intensity scales exponentially with the current per bunch. We present detailed experimental observations of the seeding effect and a model of the phenomenon. This seeding mechanism also creates potential applications as a high-power source of CSR at terahertz frequencies.

Tailored terahertz pulses from a laser-modulated electron beam

We present a new method to generate steady and tunable, coherent, broadband terahertz radiation from a relativistic electron beam modulated by a femtosecond laser. We have demonstrated this in the electron storage ring at the Advanced Light Source. Interaction of an electron beam with a femtosecond laser pulse copropagating through a wiggler modulates the electron energies within a short slice of the electron bunch with about the same duration of the laser pulse. The bunch develops a longitudinal density perturbation due to the dispersion of electron trajectories, and the resulting hole emits short pulses of temporally and spatially coherent terahertz pulses synchronized to the laser. We present measurements of the intensity and spectra of these pulses. This technique allows tremendous flexibility in shaping the terahertz pulse by appropriate modulation of the laser pulse.

Wavelet multiresolution analysis of the three vorticity components in a turbulent far wake

The main objective of the present study is to examine the characteristics of the vortical structures in a turbulent far wake using the wavelet multiresolution technique by decomposing the vorticity into a number of orthogonal wavelet components based on different central frequencies. The three vorticity components were measured simultaneously using an eight-wire probe at three Reynolds numbers, namely 2000, 4000, and 6000. It is found that the dominant contributions to the vorticity variances are from the intermediate and relatively small-scale structures. The contributions from the large and intermediate-scale structures to the vorticity variances decrease with the increase of Reynolds number. The contributions from the small-scale structures to all three vorticity variances jump significantly when Reynolds number is changed from 2000 to 4000, which is connected to previous observations in the near wake that there is a significant increase in the generation of small-scale structures once the Reynolds number reaches about 5000. This result reinforces the conception that turbulence "remembers" its origin.

Scaling of longitudinal and transverse velocity increments in a cylinder wake

Longitudinal and transverse velocity increments are measured both temporally and spatially using two X-wire probes in the intermediate region of a cylinder wake over Taylor microscale Reynolds numbers in the range of 100-300. The scaling exponents of both the spatial and temporal longitudinal velocity increments agree favorably with the predictions of Kolmogorov and She and Leveque. The scaling exponents of the transverse velocity increments are considerably smaller than those of the longitudinal ones, with the values for spatial transverse velocity increments being slightly larger than the temporal ones. The difference between the scaling exponents of the longitudinal and transverse velocity increments is examined against the refined similarity hypotheses for transverse velocity increments (RSHT) proposed by Chen It is found that the RSHT can account for the difference between the scaling exponents of the longitudinal and spatial transverse velocity increments at all Reynolds numbers considered.

Modulation of Lrp action in Escherichia coli by leucine: effects on non-specific binding of Lrp to DNA

Lrp is a global regulator of metabolism in Escherichia coli that helps cells respond to changes in environmental conditions. The action of Lrp as a transcriptional activator or repressor is sometimes affected by whether the medium contains exogenous leucine. The abundance of Lrp in cells is relatively high (about 15 microM in monomer), and given the relatively high Lrp binding affinity in vitro for specific binding sites (nanomolar apparent dissociation constants), the expectation is that all binding sites will be saturated with Lrp in vivo. Here we consider the fraction of the total Lrp in cells that is free and the fraction that is bound to DNA. Using minicell-producing strains, we measured the distribution of Lrp between cytoplasm and nucleoid in cells grown under different nutritional conditions and in cells in different phases of growth. In E. coli cells grown in minimal medium to mid-log phase, the ratio of free to DNA-bound Lrp was about 0.67. This ratio decreased about threefold when the cells were grown in minimal medium supplemented with leucine. Our results also confirmed the previous finding that growth rate regulates lrp expression by as much as three to fourfold. Growth rate-regulated lrp expression, along with changes in the extent of non-specific binding, influences the level of free Lrp in vivo over a 16-fold range. We propose that the net effect of these processes is to regulate the relative concentrations of free Lrp hexadecamer and leucine-bound octamer, leading to promoter selection in response to environmental conditions.

Biosynthetic ganciclovir triphosphate: its isolation and characterization from ganciclovir-treated herpes simplex thymidine kinase-transduced murine cells

A method is described for the preparation of ganciclovir triphosphate (GCV-TP) using murine colon cancer cells (MC38) transduced with the herpes simplex virus-thymidine kinase (MC38/HSV-tk). Murine cells transduced with viral-tk contain required viral and host enzymes needed for complete cellular synthesis of this potent antiviral metabolite. Dose response studies showed optimal intracellular levels of GCV-TP occurred after exposure of MC38/HSV-tk cells to 300 microM ganciclovir for 24 h producing 7.5 nmol GCV-TP/10(6) cells. This reflects cellular accumulation of GCV-TP to levels 25-fold greater than the medium concentration of parent drug. A simple isolation scheme included methanolic extraction and anion-exchange chromatography to recover the target triphosphate. Mass spectral analysis and selective enzyme degradation provided structural confirmation of the purified product. Biological activity of the purified GCV-TP was demonstrated by competitive inhibition experiments using human DNA polymerase alpha and HSV DNA polymerase that showed substantially greater sensitivity for the viral polymerase in agreement with previous reports. The GCV-TP obtained was further used to enzymatically prepare GCV mono- and diphosphate in high yield. This method provides an easily scalable means of preparing milligram amounts of the triphosphates of pharmacologically active acyclic nucleosides like ganciclovir.

Tsetse immune responses and trypanosome transmission: implications for the development of tsetse-based strategies to reduce trypanosomiasis

Tsetse flies are the medically and agriculturally important vectors of African trypanosomes. Information on the molecular and biochemical nature of the tsetse/trypanosome interaction is lacking. Here we describe three antimicrobial peptide genes, attacin, defensin, and diptericin, from tsetse fat body tissue obtained by subtractive cloning after immune stimulation with Escherichia coli and trypanosomes. Differential regulation of these genes shows the tsetse immune system can discriminate not only between molecular signals specific for bacteria and trypanosome infections but also between different life stages of trypanosomes. The presence of trypanosomes either in the hemolymph or in the gut early in the infection process does not induce transcription of attacin and defensin significantly. After parasite establishment in the gut, however, both antimicrobial genes are expressed at high levels in the fat body, apparently not affecting the viability of parasites in the midgut. Unlike other insect immune systems, the antimicrobial peptide gene diptericin is constitutively expressed in both fat body and gut tissue of normal and immune stimulated flies, possibly reflecting tsetse immune responses to the multiple Gram-negative symbionts it naturally harbors. When flies were immune stimulated with bacteria before receiving a trypanosome containing bloodmeal, their ability to establish infections was severely blocked, indicating that up-regulation of some immune responsive genes early in infection can act to block parasite transmission. The results are discussed in relation to transgenic approaches proposed for modulating vector competence in tsetse.

Cloning and chromosomal localization of a gene encoding a novel serine/threonine kinase belonging to the subfamily of testis-specific kinases

Using reverse transcription-polymerase chain reaction (RT-PCR) with degenerate oligonucleotides corresponding to two highly conserved motifs within the protein kinase family of catalytic domains, we isolated a PCR fragment encoding a novel member of the testis-specific serine/threonine kinases (STK) from mouse male mixed germ cell mRNA. This PCR fragment recognized a 1020-bp transcript in male germ cells by northern blot analysis and was used to clone a full-length cDNA from a mouse mixed germ cell cDNA library. This cDNA has an open reading frame of 804 bases encoding a protein of 268 amino acids. This novel gene is almost identical to Stk22c, encoding a recently described testis-specific protein kinase, except for base-pair deletions that result in a shift in the coding region and an alteration of 22 amino acids (residues 109-131). Due to its homology with Stk22c, we have called this protein kinase gene Stk22d. Northern blot analysis revealed that this protein kinase is developmentally expressed in testicular germ cells and is not present in brain, ovary, kidney, liver, or early embryonic cells. We then cloned the human homologue of this protein kinase gene (STK22C) and found it to be expressed exclusively in the testis. Fluorescence in situ hybridization with both the human and mouse cDNA clones revealed syntenic localization on chromosomes 1p34-p35 and 4E1, respectively.

[The upconversion "characteristic saturation phenomenon" of ErYb:ZBLAN glass excited by 966 nm diode laser]

This paper researches the upconversion luminescence of Er:ZBLAN and ErYb:ZBLAN glasses excited by 966 nm diode laser. It is found that there is a new kind of "characteristic saturation phenomenon". It is that the log-log plot's slope of upconversion luminescence intensity upon laser power of ErYb:ZBLAN glass is decreased clearly than that of Er:ZBLAN, and both of their log-log plots are rather good straight line. This upconversion mechanism is a new kind of "diffusion-transfer" mechanism, that is energy diffusion among Yb3+ ions sequential followed by energy transfer between Er(3+)-Yb3+ ions. The "characteristic saturation phenomenon" is just resulted from energy diffusion.

Effective particle-mediated vaccination against mouse melanoma by coadministration of plasmid DNA encoding Gp100 and granulocyte-macrophage colony-stimulating factor

Particle-mediated gene delivery was used to immunize mice against melanoma. Mice were immunized with a plasmid cDNA coding for the human melanoma-associated antigen, gp100. Murine B16 melanoma, stably transfected with human gp100 expression plasmid, was used as a tumor model. Particle-mediated delivery of gp100 plasmid into the skin of naïve mice resulted in significant protection from a subsequent tumor challenge. Co-delivery of murine granulocyte-macrophage colony-stimulating factor (GM-CSF) expression plasmid together with the gp100 plasmid consistently resulted in a greater level of protection from tumor challenge. The inclusion of the GM-CSF plasmid with the gp100 DNA vaccine allowed a reduction in the gp100 plasmid dose required for antitumor efficacy. Protection from tumor challenge was achieved with as little as 62.5 ng of gp100 DNA per vaccination. Tumor protection induced by the gp100 + GM-CSF gene combination was T cell mediated, because it was abrogated in vaccinated mice treated with anti-CD4 and anti-CD8 monoclonal antibodies. In addition, administration of the gp100 + GM-CSF DNA vaccine to mice bearing established 7-day tumors resulted in significant suppression of tumor growth. These results indicate that inclusion of GM-CSF DNA augments the efficacy of particle-mediated vaccination with gp100 DNA, and this form of combined gp100 + GM-CSF DNA vaccine warrants clinical evaluation in melanoma patients.

A kinetic study of the synthesis of ascorbate fatty acid esters catalysed by immobilized lipase in organic media

The kinetics of the synthesis of L-ascorbyl laurate and L-ascorbyl palmitate catalysed by immobilized lipase from L-ascorbic acid and an acyl donor (lauric acid, palmic acid and their methyl and ethyl esters) in 2-methylbutan-2-ol have been investigated. The factors affecting the reaction rate (shaking speed, temperature, water activity, enzyme concentration as well as substrate concentration) are discussed. The reaction conditions have been optimized as follows: shaking speed 200 rev./min, temperature 55 degrees C, enzyme 17-20% (w/w of substrate) for these substrates. The most suitable substrate concentration for all of these substrates was 300 mmol/l. The reactions were modelled. For lauric acid, methyl laurate and ethyl laurate: K(m)=74.3, 48.97 and 55.8 mmol/l, respectively; and V(max)=0.010764, 0.0114, 0.01116 mmol.min(-1).g(-1), respectively. The most suitable substrate was methyl laurate. For palmic acid, methyl palmitate and ethyl palmitate: K(m)=102, 94.9 and 104 mmol/l, respectively; and V(max)=0.0417, 0.0424 and 0.0435 mmol.min(-1).g(-1), respectively. The most suitable substrate was methyl palmitate.

Temporal and spatial expression of Hoxa-2 during murine palatogenesis

1. Mice homozygous for a targeted mutation of the Hoxa-2 gene are born with a bilateral cleft of the secondary palate associated with multiple head and cranial anomalies and these animals die within 24 hr of birth (Gendron-Maguire et al., 1993; Rijli et al., 1993; Mallo and Gridley, 1996). We have determined the spatial and temporal expression of the Hoxa-2 homeobox protein in the developing mouse palate at embryonic stages E12, E13, E13.5, E14, E14.5, and E15. 2. Hoxa-2 is expressed in the mesenchyme and epithelial cells of the palate at E12, but is progressively restricted to the tips of the growing palatal shelves at E13. 3. By the E13.5 stage of development, Hoxa-2 protein was found to be expressed throughout the palatal shelf. These observations correlate with palatal shelf orientation and Hoxa-2 protein may play a direct or indirect role in guiding the palatal shelves vertically along side the tongue, starting with the tips of the palatal shelves at E13, followed by the entire palatal shelf at E13.5. 4. As development progresses to E14, the stage at which shelf elevation occurs, Hoxa-2 protein is downregulated in the palatal mesenchyme but remains in the medial edge epithelium. Expression of Hoxa-2 continues in the medial edge epithelium until the fusion of opposing palatal shelves. 5. By the E15 stage of development, Hoxa-2 is downregulated in the palate and expression is localized in the nasal and oral epithelia. 6. In an animal model of phenytoin-induced cleft palate, we report that Hoxa-2 mRNA and protein expression were significantly decreased, implicating a possible functional role of the Hoxa-2 gene in the development of phenytoin-induced cleft palate. 7. A recent report by Barrow and Capecchi (1999), has illustrated the importance of tongue posture during palatal shelf closure in Hoxa-2 mutant mice. This along with our new findings of the expression of the Hoxa-2 protein during palatogenesis has shed some light on the putative role of this gene in palate development.

Interleukin-12 gene therapy of a weakly immunogenic mouse mammary carcinoma results in reduction of spontaneous lung metastases via a T-cell-independent mechanism

In our previous studies using gene gun-mediated delivery of interleukin 12 (IL-12) cDNA in vivo, we observed T-cell-mediated regression of established murine tumors and demonstrated the induction of systemic immunity in test animals. In this study, we further characterized the antitumoral and anti-metastatic effect of this gene therapy approach by employing two murine metastatic mammary tumor models: the immunogenic TS/A adenocarcinoma and the weakly immunogenic 4T1 adenocarcinoma. In the TS/A model, gene transfer into the skin overlying an established intradermal tumor with an IL-12 cDNA expression vector resulted in complete tumor regression in 50% of mice followed by the development of immunological memory. In contrast, the growth of the intradermal 4T1 tumors was not affected by the IL-12 gene therapy protocol. However, this treatment resulted in a substantial reduction of spontaneous metastases in the lungs of 4T1 tumor-bearing mice and significantly prolonged their survival time. T cells were not required for this anti-metastatic effect, because it was also observed in nude mice and in mice depleted of CD4+ and CD8+ T cells. Tumor-draining lymph node cells obtained from 4T1 tumor-bearing mice treated with IL-12 cDNA exhibited increased natural killer (NK) activity and produced enhanced levels of interferon-gamma (IFN-gamma) compared with similar mice treated with luciferase cDNA. In addition, in vivo depletion of NK cells or neutralization of IFN-gamma resulted in partial suppression of the anti-metastatic effect of IL-12 gene therapy, suggesting the involvement of both NK cells and IFN-gamma in this effect.

[Establishment of rat submandibular gland squamous cell carcinoma induced by DMBA]

OBJECTIVE

To study carcinogenesis and development of salivary gland tumor and establish an animal model of submandibular gland (SMG) tumor.

METHODS

Histopathological study during carcinogenesis in rat SMGs using (9,10-dimethyl-1,2-benzanthracene (DMBA) was evaluated. A total of 50 male and female Sprague-Dawley (SD) rats of 8 weeks old and 180-200 g weight were obtained from the Animal Center of Henan Medical University. Under pentobarbital sodium anesthesia, the left SMGs were exposed by surgical procedure. A sponge pellet (1.0 mm x 1.0 mm x 1.0 mm, made by authors) was used as the carrier of the carcinogen. The sponge containing 2% DMBA (Fluka, Switzerland)/acetone solution was implanted into the glandular tissue of the left SMGs. Four rats (2 males and 2 females) were killed after every 2 weeks of the DMBA/sponge implantation. The same method of sponge implantation without DMBA was used at the right side of SMG as a control. All rats left were killed after 20 weeks. The SMGs were fixed in 10% formalin buffer solution for 24 hours, and embedded in paraffin, then 4 microns-thick sections were made for histopathological study.

RESULTS

The earliest tumor occurred after 4 weeks of implantation of sponge, a total of 21 lateral tumors were induced (10 females, 11 males). There was no tumor found in the controlled SMG. The peak time of tumor genesis was after 8-12 weeks of implantation, all tumors induced were squamous cell carcinomas(SCCs). The induced tumors grew slowly below the mandibles of rats, which were present as nodular masses without capsules, and the borders were not clear. They were slightly hard when palpated. The process of carcinogenesis can be described as following: squamous metaplasia of cyst-like structures occurred, then SCCs were induced and invaded surrounding tissues. No metastasis was observed in regional lymph nodes and other organs.

CONCLUSION

SCCs of SMG can be induced by implantation of DMBA. The present study supports the conclusion that all duct segments undergo squamous metaplasia, and therefore may participate in the genesis of neoplasia during experimental carcinogenesis.

Characterization of cadmium uptake in Lactobacillus plantarum and isolation of cadmium and manganese uptake mutants

Two different Cd(2+) uptake systems were identified in Lactobacillus plantarum. One is a high-affinity, high-velocity Mn(2+) uptake system which also takes up Cd(2+) and is induced by Mn(2+) starvation. The calculated K(m) and V(max) are 0.26 microM and 3.6 micromol g of dry cell(-1) min(-1), respectively. Unlike Mn(2+) uptake, which is facilitated by citrate and related tricarboxylic acids, Cd(2+) uptake is weakly inhibited by citrate. Cd(2+) and Mn(2+) are competitive inhibitors of each other, and the affinity of the system for Cd(2+) is higher than that for Mn(2+). The other Cd(2+) uptake system is expressed in Mn(2+)-sufficient cells, and no K(m) can be calculated for it because uptake is nonsaturable. Mn(2+) does not compete for transport through this system, nor does any other tested cation, i.e., Zn(2+), Cu(2+), Co(2+), Mg(2+), Ca(2+), Fe(2+), or Ni(2+). Both systems require energy, since uncouplers completely inhibit their activities. Two Mn(2+)-dependent L. plantarum mutants were isolated by chemical mutagenesis and ampicillin enrichment. They required more than 5,000 times as much Mn(2+) for growth as the parental strain. Mn(2+) starvation-induced Cd(2+) uptake in both mutants was less than 5% the wild-type rate. The low level of long-term Mn(2+) or Cd(2+) accumulation by the mutant strains also shows that the mutations eliminate the high-affinity Mn(2+) and Cd(2+) uptake system.

Cloning, expression, and characterization of cadmium and manganese uptake genes from Lactobacillus plantarum

An Mn(2+) and Cd(2+) uptake gene, mntA, was cloned from Lactobacillus plantarum ATCC 14917 into Escherichia coli. Its expression conferred on E. coli cells increased Cd(2+) sensitivity as well as energy-dependent Cd(2+) uptake activity. Both transcription and translation of mntA were induced by Mn(2+) starvation in L. plantarum, as indicated by reverse transcriptase PCR and immunoblotting. Two Cd(2+) uptake systems have been identified in L. plantarum: one is a high-affinity Mn(2+) and Cd(2+) uptake system that is expressed in Mn(2+)-starved cells, and the other is a nonsaturable Cd(2+) uptake system that is expressed in Cd(2+)-sufficient cells (Z. Hao, H. R. Reiske, and D. B. Wilson, Appl. Environ. Microbiol. 65:592-99, 1999). MntA was not detected in an Mn(2+)-dependent mutant of L. plantarum which had lost high-affinity Mn(2+) and Cd(2+) uptake activity. The results suggest that mntA is the gene encoding the high-affinity Mn(2+) and Cd(2+) transporter. On the basis of its predicted amino acid sequence, MntA belongs to the family of P-type cation-translocating ATPases. The topology and potential Mn(2+)- and Cd(2+)-binding sites of MntA are discussed. A second clone containing a low-affinity Cd(2+) transport system was also isolated.

Differential expression of Hoxa-2 protein along the dorsal-ventral axis of the developing and adult mouse spinal cord

We have used synthetic oligopeptides derived from the coding sequence of the murine Hoxa-2 protein to produce polyclonal antibodies that specifically recognize the Hoxa-2 recombinant protein. Immunohistochemical studies reveal a distinct pattern of spatial and temporal expression of Hoxa-2 protein within the mouse spinal cord which is concomitant with the cytoarchitectural changes occurring in the developing cord. Hoxa-2 protein is predominantly detected in the nuclei of cells in the ventral mantle region of 10-day-old mouse embryos. Islet-1, a marker for motor neurons was also shown to be co-localized with Hoxa-2 in nuclei of cells in this region. As development progresses from 10-days to 14-days of gestation, Hoxa-2 protein expression gradually extends to the dorsal regions of the mantle layer. The Hoxa-2 protein expression pattern changes at 16-days of embryonic development with strong expression visible throughout the dorsal mantle layer. In 18-day-old and adult mouse spinal cords, Hoxa-2 protein was expressed predominantly by cells of the dorsal horn and only by a few cells of the ventral horn. Double labeling studies with an antibody against glial fibrillary acidic protein (GFAP, an astrocyte-specific intermediate filament protein) showed that within the adult spinal cord, astrocytes rarely expressed the Hoxa-2 protein. However, Hoxa-2 and GFAP double-labeled astrocytes were found in the neopallial cultures, although not all astrocytes expressed Hoxa-2. Hoxa-2 expressing oligodendrocyte progenitor cells were also identified after double-labeling with O4 and Hoxa-2 antibodies; although cells in this lineage that have begun to develop a more extensive array of cytoplasmic processes were less likely to be Hoxa-2 positive. The early pattern of Hoxa-2 protein expression across transverse sections of the neural tube is temporally and spatially modified as each major class of neuron is generated. This congruence in the expression of the Hoxa-2 protein and the generation of neurons in the cord suggests that the Hoxa-2 protein may contribute to dorsal-ventral patterning and/or to the specification of neuronal phenotype. Dev Dyn 1999;216:201-217.

[Rat submandibular gland tumor induced by 3-methylcholanthrene]

OBJECTIVE

To study the genesis and the development of salivary gland tumor (SGT).

METHODS

SGT animal models were established by injection of 3-methylcholanthrene (3-MCA) oil solution into 40 submandibular glands of Sprague-Dawley (SD) rats, then histopathology and ultrastructure of induced tumors were observed under microscope, and immunohistochemical detection of keratin and actin was carried out.

RESULTS

32 models of submandibular gland tumors were induced successfully, with 4 rats of squamous cell carcinoma and 28 leiomyosarcoma, and the carcinogenesis of 3-MCA and tissue genesis of induced tumors were discussed.

CONCLUSION

Submandibular gland tumor can be induced by 3-MCA, and sarcoma was of high incidence.

PU.1 and Spi-B are required for normal B cell receptor-mediated signal transduction

PU.1 and Spi-B have previously been implicated in the regulation of genes encoding B cell receptor (BCR) signaling components. Spi-B-/- B lymphocytes respond poorly to BCR stimulation; PU.1-/- mice, however, lack B cells, precluding an analysis of BCR responses. We now show that PU.1+/- Spi-B-/- B cells exhibit more extensive defects than Spi-B-/- B cells, indicating that both PU.1 and Spi-B are required for normal BCR signaling. Strikingly, BCR cross-linking results in substantially reduced protein tyrosine phosphorylation in mutant B cells. Further analysis shows that Igalpha is phosphorylated and syk is recruited and becomes phosphorylated but that BLNK and PLCgamma phosphorylation are defective in mutant cells. Our data support the existence of a novel component coupling syk to downstream targets.

[Study on double antigens sandwich enzyme immunoassay for detection of Brucella specific antibodies in human and animals]

OBJECTIVE

In order to develop practicable methods for serodiagnosis, surveillance and epidemiological surveys in human and animals Brucellosis.

METHODS

A double antigens sandwich Enzyme Immunoassay (DAgS-EIA include DAgS-ELISA and DAgS-DIEA) have been developed under the basis of first production conjugate of Brucella antigen with horseradish peroxidase. Serum samples from diagnosed patients, suspected patients of Brucellosis and sheep infected with Brucella in Henan and Hebei provinces as well as from experimental animals of infected with Brucella in laboratory detected through DAgS-EIA, I-ELISA, RBPT and SAT tests.

RESULTS

Of the diagnosed and suspected Brucellosis patients, positive rates of DAgS-ELISA, RBPT, I-ELISA, DAgS-DIEA and SAT were 60.0%-62.9%, 48.6%-58.1%, 55.6%, 53.7% and 44.2% respectively; as for sheep with Brucella-infection, positive rate of the above mentioned 5 tests were 81.8%.

CONCLUSION

Results showed that DAgS-EIA were not only specific and practicable but may use for Brucella specific antibodies detection in humans and various animals with only one conjugate of Brucella antigen with horseradish peroxidase.

[Diagnostic value of serum creatine kinase MB in patients with cardiac damage after electric injuries]

OBJECTIVE

To investigate the incidence of cardiac damage and the diagnostic value of serum myocardial enzyme following electric injuries.

METHOD

32 patients with electrical contact injuries were evaluated by serial electrocardiograms (ECG), creatine kinase (CK) and creatine kinase MB isoenzyme (CK-MB) determinations. The patients were divided into two groups according to the ECG.

RESULT

17 patients showed abnormal ECG (Group A), and 15 normal ECG (Group B). Positive correlations were noted between CK, CK-MB and the size of electric burns. The difference of serum CK-MB and 1.1% of total CK (CK-MB in skeletal muscle) was defined as CK-MB difference. CK, CK-MB, CK-MB/total CK ratio and the CK-MB difference were significantly higher in group A than in group B (all P < 0.05). The CK-MB difference of 88% (15/17) patients in group A was more than 25 U/L, whereas that was 6.7% (1/15) in group B (P < 0.01). Six patients with CK-MB difference greater than 100 U/L had obvious cardiac damage.

CONCLUSION

Cardiac damage is a common complication of electric injuries. The cardiac damage could be estimated by serum CK-MB, particularly by the CK-MB difference. The CK-MB difference might be a useful indicator for evaluating the severity of the cardiac damage.

Carbocyclic analogues of the potent cytidine deaminase inhibitor 1-(beta-D-ribofuranosyl)-1,2-dihydropyrimidin-2-one (zebularine)

Three carbocylic analogues of the potent cytidine deaminase inhibitor (CDA) zebularine [1-(beta-D-ribofuranosyl)-1, 2-dihydropyrimidin-2-one, 1a] were synthesized. The selected pseudosugar templates correspond, respectively, to the cyclopentenyl moiety of neplanocin A (compound 4), the cyclopentyl moiety of aristeromycin (compound 5), and a newly designed, rigid bicyclo[3.1. 0]hexane moiety (compound 6). These three carba-nucleoside versions of zebularine were fashioned to overcome the inherent instability of the parent drug. Each target compound was approached differently using either convergent or linear approaches. The immediate precursor to the cyclopentenyl analogue 4 was obtained by a Mitsunobu coupling of pseudosugar 7 with 2-hydroxypyrimidine. The cyclopentyl analogue 5 was linearly constructed from carbocyclic amine 17, and the final target 6 was similarly constructed from the carbobicyclic amine 27. Of the three target compounds, only 5 showed a significant level of inhibition against human CDA, but it was 16 times less potent than zebularine (Ki = 38 microM vs Ki(apparent) = 2.3 microM). Although these carbocyclic analogues appeared to be more stable than zebularine, replacement of the electronegative CO4' oxygen for the less electronegative carbon in 4-6 presumably reduces the capacity of the pyrimidin-2(1H)-one ring to form a covalent hydrate, a step considered crucial for the compound to function as a transition-state inhibitor of the enzyme.

[Three-dimensional volumetric display--a new application of frequency up-conversion]

This paper discusses the present research situation and the application prospect of 3-D volumetric display technology. The possible usability and science significance of frequency up-conversion in 3-D volumetric display field are also demonstrated systematically. In ZBLAN: Pr, Yb glasses, we primarily demonstrated and achieved a new application of frequency up-conversion three dimensional volumetric display, using the two-frequency up-conversion of the rare earth ions. The efficiency of luminescence of Pr was enhanced much by the energy transfer between Pr and Yb ions.

[Determination of antioxidants BHT,BHA and PG in food with high performance liquid chromatography]

An accurate and rapid method for simultaneous determination of antioxidants butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and propyl gallate (PG) in food by reversed-phase high performance liquid chromatography was established. The sample was extracted with hexane. Being filtrated and dried by N2, the residues in evaporator was dissolved in a certain amount of water-C2H5OH (1:4, V/V) and filtered with 0.5 micron of filter membrane for HPLC analysis. The chromatographic conditions were Radial-PAK C12 column, methanol-water (92:8, V/V) mobile phase adjusted to pH = 3 with phosphoric acid and UV-280 nm detector. By using external standard method the analytical results showed that the coefficients of variation of PG,BHA and BHT were 0.61, 0.08 and 1.44 respectively, linear correlation coefficients were more than 0.999 and recoveries were 92%-98% (n = 6). The lowest detection limit was 0.5 mg/L.

A zinc finger protein required for stationary phase viability in fission yeast

Yeast cells exit the cell cycle and enter a metabolically inert stationary phase when starved for nutrients essential for normal proliferation. We have cloned a novel gene named rsv1+ (required for stationary phase viability) that is essential for fission yeast cell viability in a stationary phase induced by glucose starvation. rsv1+ encodes a 47 kDa protein with two zinc finger motifs that are partially homologous with Aspergillus nidulans CreA, Saccharomyces cerevisiae Mig1 and mammalian EGR-1/NGFI-A. Cells deleted for rsv1+ are unable to survive glucose starvation. Transcription of rsv1+ is negatively regulated by the cAMP pathway and induced by glucose starvation. Cells with the constitutively activated cAMP pathway are known to lose viability when grown to confluence or when starved for glucose. These cells are poor in rsv1+ induction and their viability loss is largely suppressed by ectopic expression of rsv1+. Thus, poor induction of rsv1+ is at least partially responsible for the viability loss. Analysis also showed that cells need to receive starvation signals before entry into the stationary phase in order to maintain viability in a glucose-poor environment.

Long-term erythropoietin expression in rodents and non-human primates following intramuscular injection of a replication-defective adenoviral vector

Erythropoietin (Epo)-responsive anemia is a debilitating complication of chronic renal failure and human immunodeficiency virus (HIV) infection that effects more than 150,000 Americans. Patients with Epo-responsive anemias are currently treated with repeated injections of recombinant human Epo. In the studies described in this report, we have examined the safety and efficacy of using a single intramuscular (i.m.) injection of replication-defective adenoviral vectors (RDAd) encoding Epo for the treatment of Epo-responsive anemias in both mice and non-human primates. Our results demonstrate that there is a threshold dose of virus (2.5-8 x 10(7) pfu/gram of body weight) which is required to obtain long-term Epo expression and polycythemia in both species. A single i.m. injection of mice with 10(9) pfu of an RDAd encoding murine Epo (AdmEpo) resulted in elevations in hematocrits from control values of 49 +/- 0.9% to treated values of 81 +/- 3%, which were stable for more than 1 year. Similarly, a single i.m. injection of a monkey with 4 x 10(11) pfu of an RDAd-encoding simian Epo (AdsEpo) resulted in elevations of hematocrits from control levels of 40% to treated levels of > or =70%, which were stable for 84 days. Intramuscular injection of monkeys with AdsEpo appeared to be safe in that we did not detect abnormalities in chest X-rays, serum chemistries, hematologic, or clotting profiles (apart from elevated hematocrits) or organ histologies during the 84-day time course of the experiment. Taken together, these results suggest the feasibility of using i.m. injection of RDAd for the treatment of Epo-responsive anemias in humans.

Restoration of the G1 checkpoint and the apoptotic pathway mediated by wild-type p53 sensitizes squamous cell carcinoma of the head and neck to radiotherapy

BACKGROUND

A significant number of squamous cell carcinomas of the head and neck (SCCHN) resist radiation treatment, the most common form of adjuvant therapy for this disease. The presence of a mutant form of the tumor suppressor gene p53 has been correlated with disruption of programmed cell death (apoptosis) and reduced cell cycle arrest, resulting in increased radiation resistance and survival.

METHODS AND RESULTS

We introduced by means of an adenoviral vector a functional p53 gene into a radiation-resistant SCCHN cell line that harbors mutant p53. Replacement of wild-type p53 restored the G1 block and apoptosis in these cells in vitro. Moreover, introduction of wild-type p53 sensitized SCCHN-induced mouse xenografts to radiotherapy in vivo.

CONCLUSION

The combination of p53 replacement gene therapy with conventional radiotherapy may treat SCCHN more effectively.

[Analysis of vitamin K1 in Cephalanoplos segetum (Bunge) Kitam by high performance liquid chromatography]

A modified method for the analysis of vitamin K1 in Cephalanoplos segetum (Bunge) Kitam, an edible wild herb, is proposed in this paper. The ground herb sample was extracted with CHCl3, followed by evaporation to dryness with nitrogen. The residue was dissolved with methanol, filtered through 0.5microm micropore membrane and then determined on a Novapak C18, 150mm x 3.9mm i.d., column with methanol/isopropanol (70:30) as mobile phase and UV-248nm as detector. Recovery was more than 95% with CV 1.23%. The method is simple and accurate without saponification, extraction and evaporation procedures as those used previously.

p53 mediated sensitization of squamous cell carcinoma of the head and neck to radiotherapy

Radiation resistant squamous cell carcinoma of the head and neck cell line JSQ-3 carries a mutant form of tumor suppressor gene p53. Treatment of these cells with an adenoviral vector containing wild-type p53 (Av1p53) was able to inhibit their growth in vitro and in vivo while having no effect on normal cells. More significantly, introduction of wtp53 also reduced the radiation-resistance level of this cell line in vitro, in a viral dose-dependent manner. Furthermore, this radiosensitization also carried over to the in vivo situation where the response of JSQ-3 cell-induced mouse xenografts to radiotherapy was markedly enhanced after treatment with Av1p53. Complete, long-term regression of the tumors for up to 162 days was observed when a single dose of Av1p53 was administered in combination with ionizing radiation, demonstrating the effectiveness of this combination of gene therapy and conventional radiotherapy. This sensitization of tumors to radiation therapy by replacement of wtp53 could significantly decrease the rate of recurrence after radiation treatment. Since radiation is one of the most prevalent forms of adjunctive therapy for a variety of cancers, these results have great relevance in moving toward an improved cancer therapy.

Evidence supporting a signal transduction pathway leading to the radiation-resistant phenotype in human tumor cells

A signal transduction pathway, involving oncogenes and their normal counterparts the proto-oncogenes, analogous to that for cell growth and differentiation has been proposed to lead to the phenotype of cellular radioresistance (RR). In this report we provide evidence demonstrating the existence of such a pathway by using antisense oligonucleotides (ASO) to reverse the RR phenotype. Utilizing ASO directed against the raf-1 gene, a central component of this proposed pathway, we were able to reverse the RR phenotype of human tumor cell lines having elevated HER-2 expression or a mutant form of Ha-ras, two genes upstream of raf-1 in signal transduction. Additionally, anti-ras ASO were able to radiosensitize HER-2 overexpressing cells. These results, which verify the presence of a signaling pathway leading to cellular RR, also have possible clinical implications for the use of ASO as a means to sensitize radioresistant tumors to radiation therapy.

[Maintenance of the auriculocephalic sulcus in total auricle reconstruction]

The auriculocephalic sulcus is important for the position and shape of a reconstructed ear. With an additional cartilage graft, the sulcus has been created in 31 cases since 1985 and the results have been satisfactory. In the first stage of auricle reconstruction while assembling and implanting cartilage framework, a piece of cartilage was buried in the subcutis of the donor site. Three months later in the second stage, after the framework was elevated, the stored cartilage was taken out, carved and fixed between the auricular framework and the periosteum of the skull, which then was covered with a retroauricular fascial flap. The raw surface was covered with skin graft.

Reversal by cytidine of cyclopentenyl cytosine-induced toxicity in mice without compromise of antitumor activity

Among nine compounds surveyed, cytidine was found to be the most effective in reversing the antiproliferative effects of cyclopentenyl cytosine (CPEC) on human T-lymphoblasts (MOLT-4) in culture. Cytidine, at concentrations of 1-25 microM, enabled cells to maintain normal logarithmic growth when added up to 12 hr after exposure to a 200 nM concentration of the oncolytic nucleoside, CPEC. The most abundant CPEC metabolite, CPEC-5'-triphosphate, is a potent [K1 approximately 6 microM] inhibitor of CTP synthetase (EC 6.3.4.2). Accumulation of this inhibitor resulted in a depletion of CTP levels to 17% of their original cellular concentration. Exogenous cytidine reversed CPEC-induced cellular cytotoxicity by suppressing the formation of CPEC-5'-triphosphate by 70%, and by partially replenishing intracellular CTP to at least 60-70% of its original concentration. In vivo, cytidine (500 mg/kg) administered intraperitoneally 4 hr after each daily dose of CPEC (LD10-LD100) for 9 days reduced the toxicity and abolished the lethality of CPEC to non-tumored mice. Of greater practical importance is the finding that, under these experimental conditions, cytidine did not curtail the antineoplastic properties of CPEC in L1210 tumor-bearing mice. Moreover, the concentration range over which CPEC exhibited antineoplastic activity was extended with cytidine administration.

Improved synthesis of zebularine [1-(beta-D-ribofuranosyl)-dihydropyrimidin-2-one] nucleotides as inhibitors of human deoxycytidylate deaminase

The 2'-deoxy (2a) and 2'-ara-fluoro (3a) derivatives of zebularine [1-(beta-D-ribofuranosyl)-dihydropyrimidin-2-one, 1a] were phosphorylated in high yield to the 5'-nucleotides 2b and 3b, respectively, and characterized by HPLC, enzyme degradation, 1H, 13C and 31P NMR, and high resolution mass spectral analysis. Their inhibitory activity against partially purified MOLT-4 deoxycytidylate deaminase (dCMPD) in the presence of the allosteric effector deoxycytidine triphosphate (dCTP) and Mg+2 ion was examined. Compounds 2b and 3b inhibited dCMPD with Ki values of 2.1 x 10(-8) M and 1.2 x 10(-8) M, respectively. The parent nucleotide, zebularine monophosphate 1b was ineffective at concentrations > 100 mumol. The effect of the nucleosides, 1a-3a, as well as tetrahydrouridine (THU) and 2'-deoxy THU (dTHU), on the cellular production of DNA precursors was examined in human MOLT-4 peripheral lymphoblasts. It was shown that 1a, 2a and 3a all elevated intracellular dCTP and TTP levels in whole cells with the most powerful effect elicited by 1a. The 2'-fluoro derivative 3a was chemically phosphorylated much more cleanly and higher yield than 2a, without the formation of diphosphorylated by-products. This compound was found to be infinitely less sensitive to acid-catalyzed degradation than 2a. Since the substitution of fluorine for hydrogen had a slight potentiating effect on the dCMPD inhibitory activity while stabilizing the compound toward acid-catalyzed and enzymatic depyrimidination, compound 3b emerges as a very attractive tool for the pharmacological modulation of pyrimidine deaminase activity.

Comparison of biochemical parameters of benzamide riboside, a new inhibitor of IMP dehydrogenase, with tiazofurin and selenazofurin

The biochemical and cytotoxic activities of the IMP dehydrogenase (IMPDH) inhibitors benzamide riboside, tiazofurin, and selenazofurin were compared. These three C-nucleosides exert their cytotoxicity by forming an analogue of NAD, wherein nicotinamide is replaced by the C-nucleoside base. The antiproliferative activities of these three agents were compared in a panel of 60 human cancer cell lines. To examine the relationship of benzamide riboside and selenazofurin to tiazofurin, COMPARE computer analysis was performed, and correlation coefficients of 0.761 and 0.815 were obtained for benzamide riboside and selenazofurin, respectively. The biochemical activities of these agents were examined in human myelogenous leukemia K562 cells. Incubation of K562 cells for 4 hr with 10 microM each of benzamide riboside, selenazofurin and tiazofurin resulted in a 49, 71, and 26% decrease in IMPDH activity with a concurrent increase in intracellular IMP pools. As a consequence of IMPDH inhibition, GTP and dGTP concentrations were curtailed. These studies demonstrated that selenazofurin was the most potent of the three agents. To compare the cellular synthesis of NAD analogues of these agents, K562 cells were incubated with 10 microM each of benzamide riboside, tiazofurin and selenazofurin after prelabeling the cells with [2,8-3H]adenosine. The results demonstrated that benzamide riboside produced 2- and 3-fold more of NAD analogue (BAD) than tiazofurin and selenazofurin did. To elucidate the effects of the three compounds on other NAD-utilizing enzymes, the inhibitory activities of purified benzamide adenine dinucleotide (BAD), thiazole-4-carboxamide adenine dinucleotide (TAD) and selenazole-4-carboxamide adenine dinucleotide (SAD) were studied in commercially available purified preparations of lactate dehydrogenase, glutamate dehydrogenase and malate dehydrogenase. TAD and SAD did not inhibit these three dehydrogenases. Although BAD did not influence lactate and glutamate dehydrogenases, it selectively inhibited 50% of malate dehydrogenase activity at a 3.2 microM concentration. These studies demonstrate similarities and differences in the biochemical actions of the three C-nucleosides, even though they share similar mechanisms of action.

Effects of IMP dehydrogenase inhibitors on the phosphorylation of ganciclovir in MOLT-4 cells before and after herpes simplex virus thymidine kinase gene transduction

We have undertaken to characterize the role of cytoplasmic 5'-nucleotidase (EC 3.1.3.5) in the phosphorylation of the anti-herpes simplex virus and anti-human cytomegalovirus agent ganciclovir (GCV) in MOLT-4 cells, a human T cell line adapted to grow in suspension culture. The rate of formation of GCV triphosphate was found to be approximately doubled by preincubation of nontransfected MOLT-4 cells with agents that cause the accumulation of IMP, such as ribavirin (20 microM) and mycophenolic acid (1 microM), and the reaction rate was found to be unaffected by high levels of thymidine (100 microM). With herpes simplex virus-1 thymidine kinase (HStk) gene-transduced MOLT-4 cells, the rate of GCV phosphorylation was approximately 40-fold faster than that in uninfected cells and, in marked contrast to uninfected cells, the reaction was significantly inhibited both by IMP dehydrogenase inhibitors and by thymidine. These latter effects appear to be the result of 1) the accumulation of high levels of dTTP in IMP dehydrogenase inhibitor-treated cells, with consequent feedback inhibition of HStk, and 2) direct competitive substrate inhibition by thymidine of the HStk-catalyzed phosphorylation of GCV. Thus, agents that enhance 5'-nucleotidase-catalyzed phosphorylation of GCV in uninfected cells do not play a similar role in HStk-transfected cells, a consequence of the quantitative predominance of the viral thymidine kinase-catalyzed reaction over that attributable to endogenous cytoplasmic 5'-nucleotidase.