[Using sequential indicator simulation method to define risk areas of soil heavy metals in farmland.]

The heavy metals in soil have serious impacts on safety, ecological environment and human health due to their toxicity and accumulation. It is necessary to efficiently identify the risk area of heavy metals in farmland soil, which is of important significance for environment protection, pollution warning and farmland risk control. We collected 204 samples and analyzed the contents of seven kinds of heavy metals (Cu, Zn, Pb, Cd, Cr, As, Hg) in Zengcheng District of Guangzhou, China. In order to overcame the problems of the data, including the limitation of abnormal values and skewness distribution and the smooth effect with the traditional kriging methods, we used sequential indicator simulation method (SISIM) to define the spatial distribution of heavy metals, and combined Hakanson index method to identify potential ecological risk area of heavy metals in farmland. The results showed that: (1) Based on the similar accuracy of spatial prediction of soil heavy metals, the SISIM had a better expression of detail rebuild than ordinary kriging in small scale area. Compared to indicator kriging, the SISIM had less error rate (4.9%-17.1%) in uncertainty evaluation of heavy-metal risk identification. The SISIM had less smooth effect and was more applicable to simulate the spatial uncertainty assessment of soil heavy metals and risk identification. (2) There was no pollution in Zengcheng's farmland. Moderate potential ecological risk was found in the southern part of study area due to enterprise production, human activities, and river sediments. This study combined the sequential indicator simulation with Hakanson risk index method, and effectively overcame the outlier information loss and smooth effect of traditional kriging method. It provided a new way to identify the soil heavy metal risk area of farmland in uneven sampling.

[High glucose promotes gap junctional communication in cultured neonatal cardiac fibroblasts via AMPK activation]

Cardiac fibroblasts are known to be essential for adaptiveresponses in the patho- genesis of cardiovascular diseases, and increased intercellular communication of myocardial cells and cardiac fibroblasts acts as a crucial factor in maintaining the functional integrity of the heart. AMP-activated kinase (AMPK) is a key stress signaling kinase, which plays an important role in promoting cell survival and improving cell function. However, the underlying link between AMPK and gap junctional communication (GJIC) is still poorly understood. In this study, a connection between AMPK and GJIC in high glucose-mediated neonatal cardiac fibroblasts was assessed using fibroblast migration, measurement of dye transfer and connexin43 (Cx43) expression. 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR) and Compound C (CC) were used to regulate AMPK activity. The levels of cell migration and Cx43 protein expression in neonatal cardiac fibroblasts increased during high glucose treatment, accompanied by developed dye transfer. In addition, high glucose induced abundant phosphorylation of AMPK. Suppression of AMPK phosphorylation using CC reduced dye transfer, cell migration and Cx43 protein expression in neonatal cardiac fibroblasts, whereas the activation of AMPK using AICAR mimicked the high glucose-mediated cell migration, Cx43 protein expression and dye transfer enhancement. AMPK appears to participate in regulating GJIC in high-glucose-treated neonatal cardiac fibroblasts, including cell migration, dye transfer, Cx43 expression and distribution.

Effects of dietary restriction on insulin resistance in obese mice

In many cases, development of insulin resistance has been linked to obesity and may contribute to mechanism of aging. The role of diet, irrespective of degree of obesity, in modulating insulin resistance and development of age degeneration disease remains uncertain. Lowered blood glucose levels are commonly associated with diet restriction (DR), which is an intervention shown to successfully retard aging and age associated disease. The effects of DR on blood glucose and insulin resistance were measured in yellow obese (A(vy)/A), lean black (a/a) mice and in another common inbred strain (B6C3F1) (at three different ages). The yellow obese mice become diabetic as a result of an insulin receptor defect which is not clearly understood. Insulin responses and radioinsulin binding were assayed in yellow obese and lean black mice fed either ad libitum (AL) or DR diets (YAL, BAL, YDR and YAL, respectively) at four different circadian intervals. The B6C3F1 controls were fed either AL (CAL) or DR (CDR) and measures were made at six circadian stages and three different ages. Within 23 days, DR produced a significant loss in body weight and a time-dependent 22-55% reduction in basal blood glucose levels in the yellow obese mice. Additionally, exogenous insulin produced circadian stage dependent (at the time of food intake) reductions in blood glucose in the YDR animals that were not present in YAL animals. (125)I-Insulin binding in liver was increased nearly 2-fold in YDR and BDR mice during the time of day that animals were active and eating. (125)I-Insulin binding was two-fold-higher in CDR mice at 4, 12 and >24 months of age. Binding decreased as a function of age in both the CAL and CDR animals. However, even in the >24 month group the CDR animals were found to have levels of binding that were as high as those found in younger CAL liver. The mechanism of action appears to be through resolution of insulin resistance by modulating an insulin receptor defect.

Relationship between DNA methylation and mutational patterns induced by a sequence selective minor groove methylating agent

Me-lex, a methyl sulfonate ester appended to a neutral N-methylpyrrolecarboxamide-based dipeptide, was synthesized to preferentially generate N3-methyladenine (3-MeA) adducts which are expected to be cytotoxic rather than mutagenic DNA lesions. In the present study, the sequence specificity for DNA alkylation by Me-lex was determined in the p53 cDNA through the conversion of the adducted sites into single strand breaks and sequencing gel analysis. In order to establish the mutagenic and lethal properties of Me-lex lesions, a yeast expression vector harboring the human wild-type p53 cDNA was treated in vitro with Me-lex, and transfected into a yeast strain containing the ADE2 gene regulated by a p53-responsive promoter. The results showed that: 1) more than 99% of the lesions induced by Me-lex are 3-MeA; 2) the co-addition of distamycin quantitatively inhibited methylation at all minor groove sites; 3) Me-lex selectively methylated A's that are in, or immediately adjacent to, the lex equilibrium binding sites; 4) all but 6 of the 33 independent mutations were base pair substitutions, the majority of which (17/33; 52%) were AT-targeted; 5) AT --> TA transversions were the predominant mutations observed (13/33; 39%); 6) 13 out of 33 (39%) independent mutations involved a single lex-binding site encompassing positions A600-602 and 9 occurred at position 602 which is a real Me-lex mutation hotspot (n = 9, p < 10(-6), Poisson's normal distribution). A hypothetical model for the interpretation of mutational events at this site is proposed. The present work is the first report on mutational properties of Me-lex. Our results suggest that 3-MeA is not only a cytotoxic but also a premutagenic lesion which exerts this unexpected property in a strict sequence-dependent manner.

N-(2-chloroethyl)-N-nitrosourea tethered to lexitropsin induces minor groove lesions at the p53 cDNA that are more cytotoxic than mutagenic

Many different N-chloroethyl-N-nitrosourea (CENU) derivatives have been synthesized in an attempt to minimize carcinogenic activity while favoring antineoplastic activity. CENU derivatives linked to the dipeptide lexitropsin (lex) showed significant changes in groove- and sequence-selective DNA alkylation inducing thermolabile N3-alkyladenines (N3-Alkyl-As) at lex equilibrium binding sites. CENU-lex sequence specificity for DNA alkylation was determined using 32P-end-labeled restriction fragments of the p53 cDNA. The adducted sites were converted into single-strand breaks by sequential heating at neutral pH and exposure to piperidine. To establish the mutagenic and lethal properties of CENU-lex-specific lesions, a yeast expression vector harboring a human wild-type p53 cDNA was treated in vitro with CENU-lex and transfected into a yeast strain containing the ADE2 gene regulated by a p53-responsive promoter. p53 mutants were isolated from independent ade- transformants. The results revealed that: (a) CENU-lex preferentially induces N3-Alkyl-A at specific lex equilibrium binding sites, the formations of which are strongly inhibited by distamycin; (b) reactivity toward Gs is still present, albeit to a lesser extent when compared to N-(2-chloroethyl)-N-cyclohexyl-N-nitrosourea and to CENU; (c) 91% of the 49 CENU-lex p53 mutations (45 of 49) were bp substitutions, 29 of which were GC-->AT transitions, mainly at 5' purine G sites; (d) all AT-targeted mutations but one were AT-->TA transversions; (e) the distribution of the CENU-lex mutations along the p53 cDNA was not random, with position 273 (codon 91), where only GC-->AT transitions were observed, being a real (n = 3, P < 0.0002) CENU-lex mutation hot spot; and (f) a shift in DNA alkylation sites between lesion spectra induced by CENU-lex and N-(2-chloroethyl-N-cyclohexyl-N-nitrosourea was associated with an increased lethality and a decreased mutagenicity, whereas no dramatic change in mutational specificity was observed. Hence, it is tempting to conclude that, in this experimental system, N3-Alkyl-A is more lethal than mutagenic, whereas O6-alkylguanine is a common premutational lesion formed at non-lex binding sites. These results suggest that CENU derivatives with virtually absolute specificity for A residues would make targeting of lethal, nonmutagenic lesions at A+T-rich regions possible, and this may represent a new strategy for the development of new chemotherapeutic agents with a higher therapeutic index.

Quantitative and qualitative analysis of DNA methylation at N3-adenine by N-methyl-N-nitrosourea

The sequence-specific alkylation of DNA by N-methyl-N-nitrosourea (MNU) has been demonstrated for the minor groove N3-methyladenine (N3-MeAde) adduct using neutral thermal hydrolysis and polyacrylamide sequencing gels. The ratio of relative yields of N7- and N3-MeAde and N7-methylguanine (N7-MeGua) is approximately 0.03:0. 15:1.00, respectively, on the basis of the gel data, and these values are comparable to relative yields determined by bulk digestion of MNU-methylated DNA when HPLC was used to analyze the individual adducts. In contrast to the methylation at N7-guanine (N7-Gua) by MNU, alkylation at Ade shows minimal sequence selectivity. Similar to the methylation at N7-Gua, formation of N3-MeAde by MNU is inhibited by 50-200 mM concentrations of NaCl and DNA binding cations, including distamycin and spermine. However, N3-MeAde formation at Ade residues within methidiumpropyl-EDTA-Fe(II) footprinted distamycin DNA affinity binding regions is selectively inhibited at low concentrations of distamycin relative to Ade sites outside of ligand binding regions, and N7-Gua within or outside the distamycin binding regions. HPLC analysis shows that distamycin also quantitatively inhibits the production of N3-methylguanine when calf thymus DNA is treated with MNU or methyl methanesulfonate. The specific inhibitory effect of distamycin, which binds in the minor groove at Ade/Thy-rich sequences, provides additional evidence that the predominant DNA lesion detected at Ade by sequencing gel analysis involves minor groove N3-MeAde modifications.

Regioselective effect of zwitterionic DNA substitutions on DNA alkylation: evidence for a strong side chain orientational preference

The incorporation of zwitterionic residues (5-substituted omega-aminoalkyl-2'-deoxypyrimidines) into DNA has been reported to bend DNA as measured by aberrant gel mobility [Strauss et al. (1996) Proc. Natl. Acad. Sci. U.S.A. 93, 9515-9520]. Herein we report that DNA methylation by N-methyl-N-nitrosourea at N7-guanine is regioselectively inhibited by point substitutions of the zwitterionic residues 5-(6-aminohexyl)-2'-deoxycytidine, 5-(6-aminohexyl)-2'-deoxyuridine, or 5-(3-aminopropyl)-2'-deoxyuridine. No inhibition is observed for DNA methylation by dimethyl sulfate. On the basis of inhibition patterns for methylation with the different zwitterionic substitutions and the different length tethers, the omega-aminoalkyl side chains prefer to adopt a conformation that points them toward the 3'-base. Molecular modeling grid searches, coupled with energy minimizations, and simulated annealing molecular dynamics studies indicate that unfavorable steric interactions with the 5'-base and backbone, as well as stabilizing electrostatic interactions with electronegative atoms on the 3'-side, are responsible for the observed conformational preference. No evidence for association of the cationic side chain with the phosphate backbone is observed. The observed bending of DNA induced by the tethered ammonium ions may simply arise from their localization in the major groove.

The design of agents to control DNA methylation adducts. Enhanced major groove methylation of DNA by an N-methyl-N-nitrosourea functionalized phenyl neutral red intercalator

An N-methyl-N-nitrosourea (MNU) moiety [CH3N(N=O)C(=O)NH-] linked to the C4'-position of the 5-substituted phenyl ring of phenyl neutral red (PNR), 2-methyl-3-amino-5-[p-[[2-[(N-nitroso-N-methylcarbamoyl)amino]ethy l] carbamoyl]phenyl]-7-(dimethylamino)phenazenium chloride (MNU-PNR), has been synthesized as an approach to design a molecule that will deliver alkylating agents with some preference to guanine (Gua) in the major groove of DNA. The PNR nucleus was chosen because previous studies suggested the following: (1) PNR binds with a slight preference for G/C rich sequences; and (2) PNR intercalates into DNA from the major groove with the 5-phenyl ring pointing out into the major groove (Müller, W., Bünemann, H., and Dattagupta, N. (1975) Eur. J. Biochem. 54, 279-291). It is demonstrated that MNU-PNR yields 2.6 and 6.0 times more N7-methylguanine (7-MeGua) than MNU at low salt (10 mM Tris buffer) and high salt (10 mM Tris buffer + 200 mM NaCl), respectively. It is also shown that the ratio of 7-MeGua (a major groove adduct) to N3-methyladenine (a minor groove adduct) is approximately 5 times higher for MNU-PNR than for MNU. The yield of the 7-MeGua adduct is decreased by the coaddition of a nonmethylating analogue of MNU-PNR or NaCl, but increased in the presence of the minor groove intercalator, ethidium bromide. Using a 32P-end-labeled restriction fragment, the enhanced methylation by MNU-PNR at 7-Gua is confirmed, and it is demonstrated that the sequence-dependent formation of 7-MeGua from MNU-PNR is the same as that seen with MNU. UV, circular dichrosism, and viscosity studies are consistent with MNU-PNR binding to DNA via an intercalation-based process.

Effects of ischemia-hypoxia induced by interruption of uterine blood flow on fetal rat liver and brain enzyme activities and offspring behavior

The effects of acute perinatal ischemia-hypoxia on fetal liver and brain energy metabolism, fetal brain total free fatty acid concentration and subsequent offspring behavior were investigated in rats. Ischemia-hypoxia was induced at term either by ligation of the uterine blood vessels or submersion of the entire uterine horn in warmed saline. Fetuses of the adjacent horn served as within-dam controls for all assessments and fetuses of dams which had not undergone the surgical stress served as independent controls for enzyme assays. Ischemia-hypoxia was associated with reduced activity of fatty acid synthase in the liver and brain. Total free fatty acid concentration significantly increased in the fetal hypoxic brain. Pups not used for enzyme analyses were cross-fostered for behavioral assessments. Relative to the enzymatic alterations, there were few behavioral alterations associated with ischemia-hypoxia. At postnatal day 30, rats made hypoxic by ligation of the uterine blood vessels had decreased caudate nucleus and brain stem weights relative to within-dam controls. At postnatal day 85, rats made hypoxic by submersion of the uterine horn had decreased olfactory bulb weight. The results of this study indicate an initial acute response to a brief period of ischemia-hypoxia at term pregnancy in the fetal rat brain and liver.

Characterisation of circulating chromogranin A in human cancer patients

The structure of circulating chromogranin A (CgA) of phaeochromocytoma patients was characterised and compared with that of CgA extracted from tumours. Size exclusion chromatography experiments provided evidence that CgA is present in the blood of different patients, as well as in tumour extracts, as multiple forms having different hydrodynamic sizes of 600 kDa (CgA-I), 100 kDa (CgA-II) and 55 kDA (CgA-III). The amount of each CgA form as a proportion of the total antigenic material was different in different patients. Western blot analysis of chromatographic fractions indicated that these forms are made up by polypeptides of similar molecular weight (about 60-70 kDa). All CgA forms express the epitopes recognised by two monoclonal antibodies (A11 and B4E11), directed against residues 68-70 and 81-90 of human CgA. However, their relative immunoreactivity was markedly different. No evidence for the presence of multimeric complexes in the CgA-I fraction was obtained by various immunological and biochemical methods. These results suggest that circulating CgA in phaeochromocytoma patients consists of at least three forms that appear to be made up by polypeptides with similar molecular weight and different hydrodynamic properties and immunoreactivity. We hypothesise that different conformations and shapes contribute to the heterogeneity of circulating CgA.

Reaction of N-(2-chloroethyl)-N-nitrosoureas with DNA: effect of buffers on DNA adduction, cross-linking, and cytotoxicity

N-(2-Chloroethyl)nitrosoureas (CNU) are clinically used anticancer drugs whose cytotoxicity is associated with the generation of DNA interstrand cross-links. While studying the sequence selectivity for a series of CNU, a dramatic increase in the formation of N7-alkyldeoxyguanosine was observed when Tris buffer was used rather than phosphate or cacodylate buffers. Moreover, the formation of N7-alkyldeoxyguanosine lesions continues in Tris long after all of the CNU has hydrolyzed. These effects are not seen with the monofunctional alkylating analogues, e.g., N-methyl- and N-(2-hydroxyethyl)-N-nitrosourea. In order to determine if the nature of the CNU-mediated DNA damage was altered by Tris, studies were initiated on the following: (1) alkylation of N7-G in end-labeled DNA restriction fragments; (2) covalent modification of DNA with [ethyl-3H]-N-(2-chloroethyl)-N-nitrosourea; and (3) cytotoxicity in L1210 cells. The data presented demonstrate that Tris increases the yield of the "normal" CNU monofunctional cross-linked adducts, i.e., N7-(2-hydroxyethyl)deoxyguanosine, N7-(2-chloroethyl)deoxyguanosine, O6-(2-chloroethyl)deoxyguanosine, and bifunctional adducts, i.e., 1-(deoxycytid-3-yl)-2-(deoxyguanosin-1-yl)ethane and 1,2-bis(deoxyguanosin-7-yl)ethane. In addition, CNU appears to react with Tris to give a long-lived alkylating intermediate that affords large amounts of DNA adducts not seen with CNU in the absence of Tris. However, in vivo toxicity of CNU in L1210 cells is not affected by the presence of Tris, indicating that the reaction pathway(s) responsible for cross-linking is not significantly sensitive to the nature of the buffer.

[Mechanism and prevention of hemolysis in jaundiced infants in phototherapy]

It has been reported that the prolonged phototherapy results in decreased glutathione reductase (GR) activity in red blood cells. We found short-term phototherapy had the same side-effect. Besides it aggravates hemolysis of newborns during the therapy. This side-effect can be prevented by oral administration of Vit B2. Eighteen jaundiced infants who were given Vit B2 5mg three times a day during the phototherapy, and the control group of 16 patients were not given Vit B2. The results showed that the decrease of hemoglobin and the time of jaundice disappearance during the phototherapy were more favourable in the oral Vit B2 group than those of the control. These results indicated that the short-term phototherapy not only results in decreased GR activity in red blood cell, but also results in hemolysis of the newborn. This side-effect can be prevented by oral administration of Vit B2.

Acute toxicity of ganciclovir: effect of dietary restriction and chronobiology

The effect of diet, age and time of dose delivery on the mortality of female B6C3F1 mice from ganciclovir sodium (DHPG) was determined for both single (SD; 400 mg DHPG/kg, ip) and multiple doses (MD; same dose ip for 10 additional days) of the drug. Young (7-10 months) and middle-aged (MA; 19-22 months) mice (B6C3F1), both fed ad lib. (AL) and calorie restricted (CR), were dosed at 0, 6, 12 and 18 hr after lights on (HALO; SD study) and at 12.00 hr (MD study). The SD study mortality rate was 38% (AL) and 1.7% (CR) (P < 0.00001). Mortality was 53% (AL, young; P < 0.00001), over 20% (AL, MA), over 1.8% (CR, MA; P = 0.00004) or more than 1.7% (CR, young; P = 0.00002). Effects were independent of lean body mass differences between AL and CR mice. In the SD study, comparing AL mice only, the greatest mortality was seen in young mice at 6 HALO, (73%; P = 0.0034) and lowest mortality in MA mice at 12 HALO (8%; P = 0.026), whereas in the MD study mortality was 63% AL and 33% CR (P = 0.015). By age, MD mortality was 80% (AL, young; P = 0.0035), 50% (CR, MA), 47% (AL, MA), and 15% (CR, young; P = 0.0013). CR protected both young and MA mice in SD and young mice in MD. Lowest mortality for AL was at 12 HALO. It is suggested that dosing at 12 HALO may protect by decreasing DHPG uptake during a period of minimal DNA synthesis in the affected organ(s). CR and timing of DHPG dose may obviate the necessity to discontinue DHPG because of toxicity in humans. The most significant finding of this study is the impact of diet on mortality.

Groove- and sequence-selective alkylation of DNA by sulfonate esters tethered to lexitropsins

A series of sulfonate esters that are attached to a noncationic minor-groove-binding N-methylpyrrole dipeptide (Lex) related to netrospin have been synthesized. The compounds prepared differ in two respects: (1) the length [(CH2)2 vs (CH2)8] of the tether between the DNA affinity binding portion of the molecule and the sulfonate ester and (2) whether a methyl group [MeOSO2(CH2)n-Lex] or the dipeptide including the aliphatic tether [MeSO2O(CH2)n-Lex] is covalently transferred to the DNA. The DNA-cleavage patterns of these bimolecular alkylating compounds have been mapped in 32P-end-labeled restriction fragments using neutral thermal hydrolysis and alkali treatment to expose single-strand breaks at bases with thermally labile modifications. In contrast to the alkylation of DNA by simple alkyl alkanesulfonate esters, that predominantly yield major-groove alkylation at N7-guanine, the modification of DNA by MeOSO2(CH2)n-Lex and MeSO2O(CH2)n-Lex occurs primarily at N3-adenine residues associated with previously footprinted Lex DNA affinity binding regions. The ratio for the formation of N3-methyladenine (minor groove) to N7-methylguanine (major groove) in calf thymus DNA is 1:7 for dimethyl sulfate, while only the former adenine product is observed with MeSO2O(CH2)n-Lex indicating the change in groove specificity. DNA cleavage by MeOSO2(CH2)n-Lex and MeSO2O(CH2)n-Lex is efficiently inhibited by the coaddition of distamycin; however, only the DNA damage generated by the latter is blocked by NaCl. As expected, increasing the length of the (CH2)n tether from n = 2 to n = 8 moves the alkylation site by 1-2 base pairs further from the affinity binding domain. Finally, a comparison of the methylation patterns of MeOSO2(CH2)n-Lex as a function of tether length provides an insight into Lex sequence and orientational preferences.

DNA crosslinking, sister chromatid exchange and cytotoxicity of N-2-chloroethylnitrosoureas tethered to minor groove binding peptides

Chloroethylnitrosoureas (CENU) are clinically important chemotherapeutic agents whose mechanism of action involves the formation of interstrand DNA crosslinks via an ethane bridge between N1-G and N3-C. CENU generally alkylate G at the N7- and O6-positions, with the latter lesion being the precursor to the interstrand crosslink. In previous studies, we reported the synthesis of CENU appended by a C2H4 linker to the N-terminus of DNA minor groove binding dipeptides (lex, information reading peptides) based on N-methylpyrrole-carboxamide subunits. Because of the dipeptide structure, these CENU-lex's react with DNA at adenines associated with lex equilibrium binding sites. No other CENU has been reported to yield A adducts. The biological evaluation of these CENU-lex's show that they are somewhat less cytotoxic than their simpler counterparts. In addition, in vitro studies show that the minor groove binding CENU-lex's afford a lower level of sister chromatid exchange (SCE) in 9L cells that are sensitive to CENU. There is no difference between CENU-lex in SCE induction in 9L-2 cells that are resistant to CENU. Formation of DNA interstrand crosslinks from the CENU-lex's is lower than for their nonaffinity binding analogs in low ionic strength buffer, but similar in the same buffer containing 200 mM NaCl. Salt inhibits crosslinking for all CENU, but distamycin, a competitive inhibitor of lex minor groove binding, uniquely enhances crosslinks for the CENU-lex's. These results are consistent with the novel minor groove adduction being a 'detoxification' pathway for the CENU-lex's since this lesion is formed at the expense of the cytotoxic major groove interstrand crosslink.

Parvovirus H-1 P38 promoter requires the trans-activation region (tar), an SP1 site, and a TATA box for full activity

In the parvovirus H-1 P38 promoter, there are sequences identified as a TATA box, an SP1 site, and a trans-activation responsive element (tar). It was previously shown that the parvovirus H-1 nonstructural protein NS1 positively regulates the expression of the P38 promoter for the viral capsid protein gene via the tar. To characterize the tar element further, a series of single-point mutations of the tar was constructed and the mutants were compared to wild-type for the trans-activation of the P38 promoter using a cat reporter gene. Most of the tar mutations had a negative effect on the P38 promoter and some of them reduced activity as much as 70%. However, when several mutants with multiple-point mutations in the tar were tested, no significant additive effect was observed. We examined the function of the SP1 site in the trans-activation of the P38 promoter by replacing the wild-type SP1 sequence with synthetic DNA fragments, OSP1 or 2SP1, containing no SP1 or two SP1 sites respectively, in a P38 construct with a cat reporter gene. The results indicate that P38 expression varies in proportion to the number of SP1 sites, suggesting a role for the SP1 site during trans-activation by NS1. The role of the TATA box on the P38 promoter was also examined by mutagenizing TATA to CACG. The activity of this promoter was reduced to 43%. When a construct mutated at both the SP1 and TATA box sites was tested for its activity, about 22% of the wild-type activity remained, implying that this remaining activity was contributed largely by the tar element. A model is proposed for how the tar element activates the wild-type and SP1-TATA minus promoters in the presence of NS1.

N-(2-chloroethyl)-N-nitrosoureas covalently bound to nonionic and monocationic lexitropsin dipeptides. Synthesis, DNA affinity binding characteristics, and reactions with 32P-end-labeled DNA

The synthesis and characterization of a series of compounds that contain an N-alkyl-N-nitrosourea functionality linked to DNA minor groove binding bi- and tripeptides (lexitropsins or information-reading peptides) based on methylpyrrole-2-carboxamide subunits are described. The lexitropsins (lex) synthesized have either a 3-(dimethylamino)propyl or propyl substituent on the carboxyl terminus. The preferred DNA affinity binding sequences of these compounds were footprinted in 32P-end-labeled restriction fragments with methidiumpropyl-EDTA.Fe(II), and in common with other structural analogues, e.g., distamycin and netropsin, these nitrosoureas recognize A-T-rich runs. The affinity binding of the compound with the dimethylamino terminus, which is ionized at near-neutral pH, appeared stronger than that observed for the neutral dipeptide. The sequence specificity for DNA alkylation by (2-chloroethyl)nitrosourea-lex dipeptides (Cl-ENU-lex), with neutral and charged carboxyl termini, using 32P-end-labeled restriction fragments, was determined by the conversion of the adducted sites into single-strand breaks by sequential heating at neutral pH and exposure to base. The DNA cleavage sites were visualized by polyacrylamide gel electrophoresis and autoradiography. The alkylation of DNA by Cl-ENU-lex was compared to that by N-(2-chloroethyl)-N'-cyclohexyl-N-nitrosourea (CCNU), which has no DNA affinity binding properties. While all the Cl-ENU compounds generate DNA breaks as a consequence of the formation of N7-alkyl-guanine, the Cl-ENU-lex compounds induced, in a time- and dose-dependent fashion, intense DNA cleavage bands at adenine, cytosine, and thymine residues associated with affinity binding sites. These non-G cleavages induced by Cl-ENU-lex were inhibited by the coaddition of distamycin at concentrations that did not affect G alkylation break sites. CCNU, even at much higher concentrations, does not generate any similar detectable lesions at non-G sites. Therefore, linking the Cl-ENU moiety to minor groove binders is a viable strategy to qualitatively and quantitatively control the delivery and release of the ultimate DNA alkylating agent in a sequence-dependent fashion.

[Some factors influencing the determination of the softening point of plaster]

A study has been carried out on the factors influencing the softening point of plaster, such as the de-coherence, the fusing time, the cooling time, the point of constant temperature and the rate of rise in temperature. It seems feasible to determine the softening point by a mixture of vaseline and beeswax as the de-coherence when the temperature is kept at 3 degrees C/min.