Intercalated cytosine motif and novel adenine clusters in the crystal structure of the Tetrahymena telomere

The cytosine-rich strand of the Tetrahymena telomere consists of multiple repeats of sequence d(AACCCC). We have solved the crystal structure of the crystalline repeat sequence at 2.5 A resolution. The adenines form two different and previously unknown clusters (A clusters) in orthogonal directions with their counterparts from other strands, each containing a total of eight adenines. The clusters appear to be stable aggregates held together by base stacking and three different base-pairing modes. Two different types of cytosine tetraplexes are found in the crystal. Each four-stranded complex is composed of two intercalated parallel-stranded duplexes pointing in opposite directions, with hemiprotonated cytosine-cytosine (C.C+) base pairs. The outermost C.C+base pairs are from the 5'-end of each strand in one cytosine tetraplex and from the 3'-end of each strand in the other. The A clusters and the cytosine tetraplexes form two alternating stacking patterns, creating continuous base stacking in two perpendicular directions along the x - and z -axes. The adenine clusters could be organizational motifs for macromolecular RNA.

[Expression of human SRY gene and the DNA-binding property of its product]

OBJECTIVE

To investigate the role which human SRY gene plays in the regulation of the downstream gene.

METHODS

The fragment of SRY (sex determinating region on the Y chromosome) HMG domain was cloned into the expressing vector pET-15b. The hSRY gene recombinant plasmid-pETSY was transformed and expressed in E.coliBL21. The target protein was purified by pET His. Tag system. The DNA-binding retardation test and its competitive reaction were conducted between SRY protein and the fragment of Mullerian inhibiting substance (MIS) promoter.

RESULTS

The molecular weight of the expressed hSRY protein was shown to be approximately 21kD. The specific DNA binding property of SRY protein to the fragment of MIS was confirmed in the retardation test and its competitive reaction.

CONCLUSION

The results suggest that the product of SRY gene can bind the MIS promoter region and may initiate the transcription of MIS.

[Effect of Yangxue bushen tablet on ovarian function in animal model of Yang deficiency]

OBJECTIVE

To study the therapeutic mechanism of Yangxue Bushen tablet (tablet for nourishing blood and tonifying Kidney) on the Kidney deficiency type of functional amenorrhea and infrequent menstruation.

METHODS

Applied with orimeten, models of Yang deficiency in female rabbits were made, ikaclomine was taken as the control drug. Group I was the group of animal model of Yang deficiency; Group II was the ikaclomine treatment group; Group III was the high dosage treatment group; Group IV was the low dosage group; Group V normal rabbit treated with distilled water. The functional effect of gonadal axis was evaluated by the changes of the signs of animal histomorphology of ovary and uterus, and the level of beta-endorphin.

RESULTS

The animals of Yang deficiency in Group II, III and IV recovered as a whole, and the changes of different levels of folliculi, morphosis of endometria and deciduous vaginal epithelial cell in group II, III and IV were more obviously than those in group I and V (P < 0.05). The content of beta-endorphin in blood plasma in group I was 106.6 pg/ml, which was lower than those in the other groups (P < 0.05), and the contents of beta-endorphin in blood plasma, in group III, IV and II were similar to that in group V (P < 0.05).

CONCLUSION

Yangxue Bushen tablet has the effect on regulating menstruation by regulating the function of gonadal axis, regulating and promoting the ovarian function.

Protective role of zinc-metallothionein on DNA damage in vitro by ferric nitrilotriacetate (Fe-NTA) and ferric salts

Oxidative DNA damage can be caused by radicals generated by transitional metals like iron in Fenton reaction. Metallothionein (MT) may play an important role in preventing oxidative DNA damage. Therefore, after comparing the effects of ferric salts (Fe), and complexes of ferric salts with nitrilotriacetic acid (Fe-NTA) on DNA damage, the protective effects of zinc-MT (Zn-MT) on DNA damage of Fe salts or Fe-NTA were investigated in vitro. DNA damage was measured by loss of fluorescence of DNA binding to ethidium bromide, and also by increased DNA mobility in agarose gel electrophoresis. Both Fe salts and Fe-NTA could induce calf thymus DNA damage in presence of hydrogen peroxide and ascorbate. However, the degree of DNA damage was lower with Fe salts than that with Fe-NTA complex. Addition of 50 microM Zn-MT could only protect DNA from Fe-NTA, but not from Fe salt induced damage. The protective effect of MT was about five times better than that of glutathione (GSH). These results suggest a potential role for MT in protection from Fe-NTA-induced DNA damage.

Interferometer for small-angle measurement based on total internal reflection

We describe a new method for angle measurement based on the internal-reflection effect and heterodyne interferometry. A novel prism assembly is designed that can always parallel retroreflect the incoming light beams so the optical configuration is compact. As a differential common-path optical configuration is integrated into the design, the linearity of the method is greatly improved. Details of theoretical analysis of the method and experimental verification of the principle are presented. The resolution can be better than 0.3 arc sec. The experimental results and further improvements of the proposed method are also addressed.

Effects of gamma radiation on levels of brain metallothionein and lipid peroxidation in transgenic mice

The induction of metallothionein (MT) synthesis in the brain was investigated in MT-I isoform-overexpressing transgenic (MT-I*) and control mice after exposure to increasing doses of 2 to 20 Gy of whole-body gamma radiation. Although the MT-I isoform was the major isoform of MT in this transgenic mouse, the other isoforms, MT-II and MT-III, were also present in the brain. The total concentration of MT in the brain was measured by a cadmium-binding assay, while zinc and lipid peroxides were measured by atomic absorption spectrophotometry and by the thiobarbituric acid method, respectively. In MT-I* mice at 24 h after radiation exposure, the level of MT in the brain was increased from a basal level of 44.4 +/- 4.0 microg/g to a maximum level of 91.0 +/- 9.0 microg/g after 5 Gy and remained high after 10 and 20 Gy. In a time-course experiment with 5 Gy, the concentration of MT in the brain of MT-I* mice increased at 3 h and reached a maximum of 175.3 +/- 15.3 microg/g at 6 h. This high level of MT remained unchanged for 48 h after radiation exposure. Metallothionein was not induced markedly in the brains of control mice either at 24 h after exposure to 2-20 Gy gamma radiation or at different times after exposure to 5 Gy gamma radiation. In both strains of mice, the total concentration of zinc in the brain decreased with increasing radiation dose. No differences in lipid peroxide levels were seen in control mice exposed to 5 Gy at 6 and 12 h or after exposure to three other doses (2, 10 and 20 Gy) at 24 h. Slight increases (1.35 and 1.22, respectively) in lipid peroxide levels were observed in control mice at 24 and 48 h after exposure to 5 Gy. Lipid peroxide levels in the brain were not changed in irradiated MT-I* mice. The results show a marked increase in the levels of MT in the brain of transgenic mice after exposure to gamma radiation. The induced synthesis of MT may be only one of several mechanisms that prevent the induction of lipid peroxidation in the brain by gamma radiation.

[Prognosis of laryngeal carcinoma in youth]

The prognosis of 55 cases of laryngeal carcinoma in young people had been studied. The major factors mainly related to prognosis were smoking and misdiagnosis, while the tumour differentiation might be not so important. There was a high recurrence rate of 25.5% in the young patients and low 3- and 5-year survival rates of 47.4% and 34.5% respectively. The mortality of 1-year after surgery was 21.8%. The 3-and 5-year survival rates between total and partial laryngectomy made no difference. The survival rate of patients with positive node was lower. Early diagnosis is most important for young patients. Partial laryngectomy and neck dissection must be performed as far as possible.

[Interleukin-6 gene cloning, expression and purification]

OBJECTIVE

The main purpose of this paper is to study the batch production of recombinant human interleukin-6(rhIL-6).

METHODS

The cloned rhIL-6 gene is under the control of T7 promoter of pET30a vector and expressed in E. coli.

RESULTS

The ratio of expressed recombinant protein to total cell protein is more than 50%. The rhIL-6 molecular weight is 21,000, isoelectric point is 6.7. The purity of the rhIL-6 is more than 95%, and the activity of rhIL-6, determined by IL-6 dependent mice hybridoma cell line 7TD1 and MTT assay, is 0.35 ng/ml.

CONCLUSIONS

All results mentioned show that rhIL-6 meets the request of the middle scale production.

[The calculation of transitions 4s(2)4p-4s4p(2), 4s(2)4p-4s(2)5s, 4s(2)4p-4s(2)4d, 4s4p(2)-4p(3) and 4p(3)-4s(2)5s energy levels, wavelengths and oscillator strengthes in Ga-like ions from Z X-Rh XV]

In this paper, the 4s(2)4p, 4s(2)4d, 4s4p(2), 4p(3) and 4s(2)5s configuration's energy level structures, and configuration interactions in Ga-Like from Ga I-Xe XXIV ions are analysed in theory. The law of isoelectronic series is given. By using our fitted formula, the energies of Tc XIII ion 4s(2)4p, 4s4p(2) and 4s(2)5s configurations are predicted by interpolation, the energies of Tc IIIX-Rh XV ions 4p(3) and 4s(2)4d configurations are predicted by extrapolation. Wavelengths and oscillator strengthes (HXR theoretical calculation) of transitions 4s(2)4p-4s(2)4d, 4s(2)4p-4s4p(2), 4s(2)4p-4s(2)5s, 4p(3)-4s(2)5s and 4s(2)4p-4p(3) are given. The deviations of predictive energy levels from ob served values are less than 100cm(-1).

Autofocus laser rotary encoder

A laser incremental encoder with autofocus operation isproposed. In the encoder, an optical read head focuses three laserbeams upon a disk with a scaling grating. The scaling grating is areflection grating for which the height difference between adjacentpixels is one quarter of the wavelength of the laser. Each of thetwo laser beams is focused onto one of the two sections of thereflective grating, whereby the pitch of the grating can be detected byinterferometric reflection. The third beam acts to provideautofocus and is reflected from a smooth part between the two sectionsof the reflective grating. Therefore the encoder is less sensitiveto the gap between the optical read head and the scaling grating, andno precision adjustment is required. Also, the reading data arefree from the vibration and waviness of the grating surface. In theexperiments an encoder disk was fabricated from a wafer by lithographictechniques. The encoder with an 18-mm radius of the disk can reacha resolution of 2(16) = 65,536 pulses per revolution withoutelectronic interpolation.

Protective effects of extracted human-liver RNA, a known interferon inducer, against radiation-induced cytogenetic damage in male mice

Cells in vitro or in vivo pre-exposed to low-dose radiation (LDR) or low concentrations of chemical mutagens became more resistant to large-dose radiation-induced DNA or chromosome damage. This was known as radio-adaptive response, for which the exact mechanism was unclear. However, multiple cellular and molecular responses to LDR have been documented, for instance, the induction of some cytokines such as interferon (IFN). Administration of exogenous IFN to cultured cells or mice showed marked radio-protection. In the present study, we investigated the in vivo radio-protective effects of extracted human liver RNA (HL-RNA), a known IFN inducer, indirectly to determine the radio-protective action of endogenous IFN. First, mice were administered with 6.25 mg/kg HL-RNA at different times before exposure to radiation and the 24 h pretreatment offered the optimal protective action for HL-RNA on cytogenetic effects in bone marrow cells. When the mice were treated with different concentrations of HL-RNA for 24 h, a wide dose-range (25-100 mg/kg) of HL-RNA resulted in a marked protection from X-ray-induced chromosome aberrations in both bone marrow cells and germ cells. In subsequent experiments, a protective effect of pretreatment with 25 mg/kg HL-RNA for 24 h was also found for radiation-induced micronuclei in polychromatic erythrocytes (PCE), and inhibition of DNA repair ability (unscheduled DNA synthesis, UDS). These results demonstrated that HL-RNA, an IFN inducer, is able to offer significant cytogenetic protection from radiation, implying indirectly that the induction of IFN by LDR may also play a protective role as one of the mechanisms in the induction of the cytogenetic adaptive response.

Transforming growth factor-beta1 (TGF-beta1) in penile and prostate growth in the rat during sexual maturation

The goal of this study was to determine whether transforming growth factor-beta1 (TGF-beta1) may contribute to the arrest of penile growth and the down-regulation of androgen receptors (AR) that occur during sexual maturation in the rat penis. For this purpose, body, penis, and prostate weights were obtained from male rats of increasing ages, and penis and prostate TGF-beta1 concentrations were determined by a sandwich enzyme-linked immunosorbent assay. The cytosol fraction was obtained from the shafts and glandes of immature (19-day-old) and adult (90-day-old) rat penises, and ARs were measured by a western blot assay. The effect of exogenous TGF-beta1 on penile growth was examined in vivo in two groups of immature rats (21 and 27 days old) implanted with miniosmotic pumps delivering either human TGF-beta1 or vehicle only directly into the corpora cavernosa for 6 days. The penises, prostates, and testes were weighed, and the AR content was estimated by western blot. The growth rate of the penis declined after 8 weeks of age, whereas the ventral prostate growth rate increased until 14 weeks of age and then slowed down. The content of penile AR protein decreased seven-fold in the adult rats compared to the immature animals. Penile TGF-beta1 concentration increased nearly three-fold from the 19-day-old rats to a peak at 60 days of age and then decreased over the next 4 months to the initial levels. In contrast, TGF-beta1 concentration in the prostate was not significantly affected by age and remained below the lowest penile values in all age groups. Transforming growth factor-beta1 given locally to the penis reduced penile shaft weight by 38 and 22% in two groups of immature rats, while the weights of the penile glans, testis, and ventral prostate remained unaffected. Androgen receptor content was higher in the glans than in the shaft and was not changed by TGF-beta1 treatment. These results suggest that the increase of TGF-beta1 levels in the penis may reinforce growth arrest caused by the down-regulation of penile ARs, whereas the maintenance of a high content of ARs and a low TGF-beta1 concentration may allow prostate growth to continue.

Chemical oxidation and DNA damage catalysed by inorganic sunscreen ingredients

Titanium dioxide (TiO2) has been noted (US Federal Register, 43FR38206, 25 August 1978) to be a safe physical sunscreen because it reflects and scatters UVB and UVA in sunlight. However, TiO2 absorbs about 70% of incident UV, and in aqueous environments this leads to the generation of hydroxyl radicals which can initiate oxidations. Using chemical methods, we show that all sunscreen TiO2 samples tested catalyse the photo-oxidation of a representative organic substrate (phenol). We also show that sunlight-illuminated TiO2 catalyses DNA damage both in vitro and in human cells. These results may be relevant to the overall effects of sunscreens.

[Erythropoietin gene cloning and expression in S. cerevisiae]

Mature human erythropoietin gene was amplified from EPO cDNA by PCR methods. The PCR product was cloned into pUC18 plasmid at Sma I site, then precisely engineered into a intermidiate vector pSK43SB which were digested with Hind III, Mung bean nuclease, and Sal I. Then degest pSK43SB-EPO plasmid with EcoR I and Cla I, the EC fragment with an alpha-factor leading sequence, EPO gene and CYC1 terminater were produced. It was then cloned into a typical high efficiency episomal expression vector YEpHC8. Human EPO protein with highly mannose glycosylated was identified by Western blot methods in both secreted and in cells proteins. N-Glycosidase F digested secreted EPO can produce 20,000 EPO without N-glycosylation similar with that produced in cells.

[The cloning, expression, purification and bioactivity identification of recombinant IGF-I]

The fragment containing IGF-I cDNA and cyc1 terminator from PSK-IGF-I plasmid was cloned into PSK43 SB treated by Hind III, Klenow and Cla I, generating a recombinant PSB-IGF-I (DH), which have double Hind III sites. This plasmid was treated by Hind III and Klenow, ligated to give a recombinant plasmid PSB-IGF-I(NH), which has no Hind III site. After analysed by restriction endonucleases and sequencing, the fusion site was verified to be correct. This plasmid was excised and a BamH I-Cla I fragment containing yeast alpha-factor promotor, leader sequence, IGF-I cDNA and cycl terminator was cloned into yeast episomal plasmid vector YEpHC8, generating a recombinant plasmid YEpHC8-IGF-I. Transformed this plasmid into yeast competence cells BJ1990 by using LiAc method. The expressed products were secrected into the medium broth and having the correct molecular weight of 8,100 on SDS-PAGE. The products of IGF-I were raised by using high-cell-density fermentation of Saccharomyces cerevisiae. The cleared supernatant of yeast medium was applied to Bio-Rex 70 resin, eluted with 1 mol/L ammonium acetate, pH8.0. Main peak was pooled and applied to Bio-Gel P10 (200-400 mesh). The second peak was collected and get relatively pure IGF-I proteins. The biological activities of IGF I product was assayed in NIH3T3 cells by using MTT method. The results show that the expressed IGF-I can obviously stimulate NIH3T3 cells to proliferate at the concentration ranging from 10 ng/ml to 50 ng/ml, suggesting that the protein has its biological activities.

Tissue- and development-specific expression of multiple alternatively spliced transcripts of rat neuronal nitric oxide synthase

Nitric oxide (NO) functions as an intercellular messenger and mediates numerous biological functions. Among the three isoforms of NO synthase that produce NO, the ubiquitously expressed neuronal NO synthase (nNOS) is responsible for a large part of NO production, yet its regulation is poorly understood. Recent reports of two alternative spliceforms of nNOS in the mouse and in man have raised the possibility of spatial and temporal modulation of expression. This study demonstrates the existence of at least three transcripts of the rat nNOS gene designated nNOSa, nNOSb, and nNOSc, respectively, with distinct 5' untranslated first exons that arise from alternative splicing to a common second exon. Expression of the alternative transcripts occurs with a high degree of tissue and developmental specificity, as demonstrated by RNase protection assays on multiple tissues from both fetal and adult rats. Furthermore, terminal differentiation of rat pheochromocytoma-derived PC12 cells into neurons is associated with induction of nNOSa, suggesting, likewise, development- and tissue-specific transcriptional control of nNOS isoform expression. Physical mapping using a rat yeast artificial chromosome clone shows that the alternatively spliced first exons 1a, 1b, and 1c are separated by at least 15-60 kb from the downstream coding sequence, with exons 1b and 1c being positioned within 200 bp of each other. These findings provide evidence that the biological activity of nNOS is tightly and specifically regulated by a complex pattern of alternative splicing, indicating that the notion of constitutive expression of this isoform needs to be revised.

Antimicrobial compounds from Ceanothus americanus against oral pathogens

During the search for antimicrobial compounds from higher plant sources, a methanol extract of Ceanothus americanus demonstrated antimicrobial activity against selected oral pathogens. Through further bioassay-guided fractionation and purification, three triterpenes (ceanothic acid, 27-hydroxy ceanothic acid and ceanothetric acid) and two flavonoids (maesopsin and maesopsin-6-O-glucoside) were identified. Among these, ceanothetric acid and maesopsin-6-O-glucoside were new compounds. Ceanothic acid and ceanothetric acid demonstrated growth inhibitory effect against Streptococcus mutans, Actinomyces viscosus, Porphyromonas gingivalis, and Prevotella intermedia with MICs ranging from 42 to 625 micrograms ml-1. Maesopsin, its glucoside, and 27-hydroxy ceanothic acid, were inactive below the concentration of 500 micrograms ml-1.

Induction of apoptosis in the germ cells of adult male rats after exposure to cyclophosphamide

Treatment with cyclophosphamide, a commonly used anticancer drug, may result in oligozoospermia or azoospermia. The objective of this study was to determine whether exposure of male rats to cyclophosphamide induces apoptosis in male germ cells, and if so, when the peak of apoptosis occurs and at what specific stages of spermatogenesis. The presence of apoptosis was determined by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) detection in situ and by an increase in DNA fragmentation (DNA ladder). To determine the time course of drug-induced apoptosis, male Sprague-Dawley rats were treated with a single dose (70 mg/kg BW) of cyclophosphamide, and the testes were fixed 0, 4, 8, 12, 18, 24, and 48 h after treatment. To determine the dose response, rats were treated with doses of cyclophosphamide (0, 2, 7, 20, and 70 mg/kg), and the testes were fixed 12 h after treatment. A low spontaneous incidence of apoptosis was observed in controls, in particular in premeiotic germ cells of stages I-IV and XI-XIV of the seminiferous tubules. In cyclophosphamide-exposed rats, the incidence of apoptosis increased progressively at 4 h and 8 h, reached a peak at 12 h (about 3.5-fold above control), and then decreased rapidly to control levels by 48 h. A 70-mg/kg dose of cyclophosphamide induced a significant increase in apoptosis; lower doses did not. Although drug-induced apoptosis occurred in all stages of germ cells, it was most pronounced in spermatogonia and spermatocytes in stages I-IV and XI-XIV. Thus, apoptosis may be involved in the occurrence of oligozoospermia or azoospermia after cyclophosphamide treatment. Apoptosis of damaged premeiotic germ cells may serve a critical role in protecting subsequent generations from the diverse effects of toxicants.

[The simultaneous analysis of substance P, somatostatin, neurokinin and neurotensin by capillary zone electrophoresis]

Neuropeptides play an important part in several different areas of neurochemistry. Recently, capillary electrophoresis (CE) was developed for analysis of neuropeptides. This paper reports a capillary zone electrophoretic method for the simultaneous separation and quantitative determination of the substance P (SP), somatostatin (SS), neurokinin (NKA) and neurotensin (NT). The separation was performed on a 50microm x 60cm fused-silica capillary using 0.1mol/L at pH 2.7 phosphate as buffer. The eluted fractions were detected at 214nm.

Synchrony of clonal cell proliferation and contiguity of clonally related cells: production of mosaicism in the ventricular zone of developing mouse neocortex

We have analyzed clonal cell proliferation in the ventricular zone (VZ) of the early developing mouse neocortex with a replication-incompetent retrovirus encoding human placental alkaline phosphatase (AP). The retrovirus was injected into the lateral ventricles on embryonic day 11 (E11), i.e., at the onset of neuronogenesis. Three days postinjection, on E14, a total of 259 AP-labeled clones of various sizes were found in 7 fetal brains. There are approximately 7 cell cycles between E11 and E14 (), and there is a 1-2 cell cycle delay between retroviral injection and the production of a retrovirally labeled "founder" cell; thus, we estimate that the "age" of the clones was about 5-6 cell cycles. Almost one-half of the clones (48.3%) identified were pure proliferating clones containing cells only in the VZ. Another 18.5% contained both proliferating and postproliferative cells, and 33.2% contained only postproliferative cells. It was striking that over 90% of the clonally related proliferating cells occurred in clusters of two or more apparently contiguous cells, and about 73% of the proliferating cells occurred in clusters of three or more cells. Regardless of the number of cells in the clone, these clusters were tightly packed and confined to a single level of the VZ. This clustering of proliferating cells indicates that clonally related cells maintain neighbor-neighbor relationships as they undergo interkinetic nuclear migration and progress through several cell cycles, and, as a result, the ventricular zone is a mosaic of small clusters of clonally related and synchronously cycling cells. In addition, cells in the intermediate zone and the cortical plate were also frequently clustered, indicating that they became postproliferative at a similar time and that the output of the VZ is influenced by its mosaic structure.

Local homogeneity of cell cycle length in developing mouse cortex

We have measured the amount of variation in the length of the cell cycle for cells in the pseudostratified ventricular epithelium (PVE) of the developing cortex of mice on embryonic day 14. Our measurements were made in three cortical regions (i.e., the neocortex, archicortex, and periarchicortex) using three different methods: the cumulative labeling method (CLM), the percent labeled mitoses (PLM) method, and a comparison of the time needed for the PLM to ascend from 0 to 100% with the time needed for the PLM to descend from 100 to 0%. These 3 different techniques provide different perspectives on the cytokinetic parameters. Theoretically, CLM gives an estimate for a maximum value of the total length of the cell cycle (TC), whereas PLM gives an estimate of a minimum value of TC. The difference between these two estimates indicates that the range for TC is +/-1% of the mean TC for periarchicortex, +/-7% for neocortex, and +/-8% for archicortex. This was confirmed by a lengthening of the PLM descent time in comparison with its ascent time. The sharpness of the transitions and the flatness of the plateau of the PLM curves indicate that 99% of the proliferating cells are within this narrow estimated range for TC; hence, only approximately 1% deviate outside of a relatively restricted range from the average TC of the population. In the context of the possible existence within the cortical PVE of two populations with markedly dissimilar cell cycle kinetics from the mean, one such population must comprise approximately 99% of the total population, and the other, if it exists, is only approximately 1% of the total. This seems to be true for all three cortical regions. The narrow range of TC indicates a homogeneity in the cell cycle length for proliferating cells in three different cortical regions, despite the fact that progenitor cells of different lineages may be present. It further predicts the existence of almost synchronous interkinetic nuclear movements of the proliferating cells in the ventricular zone during early development of the cerebral cortex.

Construction and characterization of a 10-genome equivalent yeast artificial chromosome library for the laboratory rat, Rattus norvegicus

Increasing attention has been focused in recent years on the rat as a model organism for genetic studies, in particular for the investigation of complex traits, but progress has been limited by the lack of availability of large-insert genomic libraries. Here, we report the construction and characterization of an arrayed yeast artificial chromosome (YAC) library for the rat genome containing approximately 40,000 clones in the AB1380 host using the pCGS966 vector. An average size of 736 kb was estimated from 166 randomly chosen clones; thus the library provides 10-fold coverage of the genome, with a 99.99% probability of containing a unique sequence. Eight of 39 YACs analyzed by fluorescence in situ hybridization were found to be chimeric, indicating a proportion of about 20-30% of chimeric clones. The library was spotted on high-density filters to allow the identification of YAC clones by hybridization and was pooled using a 3-dimensional scheme for screening by PCR. Among 48 probes used to screen the library, an average of 9.3 positive clones were found, consistent with the calculated 10-fold genomic coverage of the library. This YAC library represents the first large-insert genomic library for the rat. It will be made available to the research community at large as an important new resource for complex genome analysis in this species.

Cancer chemopreventive activity of resveratrol, a natural product derived from grapes

Resveratrol, a phytoalexin found in grapes and other food products, was purified and shown to have cancer chemopreventive activity in assays representing three major stages of carcinogenesis. Resveratrol was found to act as an antioxidant and antimutagen and to induce phase II drug-metabolizing enzymes (anti-initiation activity); it mediated anti-inflammatory effects and inhibited cyclooxygenase and hydroperoxidase functions (antipromotion activity); and it induced human promyelocytic leukemia cell differentiation (antiprogression activity). In addition, it inhibited the development of preneoplastic lesions in carcinogen-treated mouse mammary glands in culture and inhibited tumorigenesis in a mouse skin cancer model. These data suggest that resveratrol, a common constituent of the human diet, merits investigation as a potential cancer chemopreventive agent in humans.