Acute lead intoxication in a pregnant mare

Lead (Pb) intoxication in horses is usually a chronic phenomenon with clinical signs associated with central nervous dysfunction. This report gives details of a case of acute Pb intoxication in a 9-year-old American Saddlebred mare with severe, progressive and ultimately fatal neurological deterioration. During the 4 days of hospitalisation, clinical signs progressed from intermittent headshaking and depression to severe, continuous, uncontrollable manic behaviour. At autopsy, three grey-coloured, hard metal particles were present in the gastrointestinal tract and subsequently found to contain 2614 ppm Pb. Lead concentrations in the brain, liver, stomach and kidney were 29, 4, 6 and 2 ppm wet weight, respectively.

Elliptic flow in Au+Au collisions at square root(S)NN = 130 GeV

Elliptic flow from nuclear collisions is a hadronic observable sensitive to the early stages of system evolution. We report first results on elliptic flow of charged particles at midrapidity in Au+Au collisions at square root(S)NN = 130 GeV using the STAR Time Projection Chamber at the Relativistic Heavy Ion Collider. The elliptic flow signal, v2, averaged over transverse momentum, reaches values of about 6% for relatively peripheral collisions and decreases for the more central collisions. This can be interpreted as the observation of a higher degree of thermalization than at lower collision energies. Pseudorapidity and transverse momentum dependence of elliptic flow are also presented.

Measurement of proliferation activity in human melanoma xenografts by magnetic resonance imaging

Tumor proliferation may be predictive for malignant progression and response to fractionated therapy of cancer. The purpose of the present work was to investigate whether the proliferation activity of solid tumors can be assessed in vivo from the proton relaxation times, T1 and T2. Tumors of four amelanotic human melanoma xenograft lines were studied. Three parameters were used to represent tumor proliferation activity; the volume doubling time, Tvol, the potential doubling time, Tpot, and the fraction of cells in S-phase. Tvol was determined from volumetric growth data. Tpot and S-phase fraction were determined by flow cytometric analysis of tumor cells after bromodeoxyuridine (BrdU) incorporation in vivo. T1 and T2 were measured by 1H-MRI in vivo, using spin-echo pulse sequences. The proliferation parameters and relaxation times differed considerably among the tumor lines. Significant correlations were found between the proliferation parameters and the relaxation times, regardless of whether Tvol, Tpot, or S-phase fraction was considered. Tumors with short Tvol and Tpot and high S-phase fraction had long T1 and T2 compared to tumors with long Tvol and Tpot and low S-phase fraction. The elongated T1 and T2 of fast growing tumors were probably due to increased interstitial and/or intravascular water content. The present results suggest that in vivo spin-echo 1H-MRI can be used to discriminate between tumors of high and low proliferation activity.

Propidium iodide quenches the fluorescence of TdT-incorporated FITC-labeled dUTP in apoptotic cells

Apoptotic cells with frequent DNA strand breaks may be detected by tagging with directly or indirectly labeled nucleotides incorporated by the use of terminal deoxynucleotidyl transferase (TdT). Propidium iodide (PI) is typically added for the simultaneous assessment of DNA content. PI was found to quench the specific in situ FITC-fluorescence of apoptotic cells which were labeled by TdT with FITC-conjugated dUTP, biotin-dUTP followed by streptavidin-FITC, or digoxigenin-dUTP followed by FITC-labeled anti-digoxigenin antibodies as measured by flow cytometry. The effect was concentration-dependent, with 50% quenching occurring at 0.8 microg/ml, 1.5 microg/ml, and 5 microg/ml PI, respectively, at approximately 1 x 10(6) cells/ml. Spectrofluorimetry in solution revealed that 15 microg/ml PI was required to quench 50% of the fluorescence of ss FITC-labeled poly(dU)35. In contrast, the fluorescence of ds FITC-labeled poly(dU)35-poly(dA) was quenched to 50% at 3 microg/ml PI. The maximum of the fluorescence excitation spectrum of PI shifted from 490 nm to 535 nm upon binding to ds DNA as well as ss poly(dU)35, and the fluorescence yield of PI at 610 nm increased, but the binding required 10-fold higher concentrations of poly(dU)35 as compared to ds DNA. The spectroscopic properties of PI are therefore similar whether bound to poly(dU) or to double-stranded DNA, but the binding to poly(dU) is much weaker. The observed quenching in situ therefore cannot be explained by direct binding of PI to the poly(dU) tails synthesized by TdT in situ in apoptotic cells, but may rather be due to radiationless energy transfer from FITC to PI bound to double-stranded DNA close to the nicks where TdT is known to start polymerization.

Hypoxia induces p53 accumulation in the S-phase and accumulation of hypophosphorylated retinoblastoma protein in all cell cycle phases of human melanoma cells

Hypoxia has been shown to induce accumulation of p53 and of hypophosphorylated retinoblastoma protein (pRb) in tumour cells. In this study, the cell cycle dependence of p53 accumulation and pRb hypophosphorylation in four human melanoma cell lines that are wild type for p53 was investigated using two-parameter flow cytometry measurements of p53 or pRb protein content and DNA content. The hypoxia-induced increase in p53 protein was higher in S-phase than in G1 and G2 phases in all cell lines. The accumulation of p53 in S-phase during hypoxia was not related to hypoxia-induced apoptosis or substantial cell cycle specific cell inactivation during the first 24 h of reoxygenation. pRb was hypophosphorylated in all cell cycle phases by hypoxia treatment. The results did not support a direct link between p53 and pRb during hypoxia because p53 was induced in a cell cycle-specific manner, whereas no cell cycle-dependent differences in pRb hypophosphorylation were detected. Only a fraction of the cell populations (0.60+/-0.10) showed hypophosphorylated pRb. Thus, pRb is probably not the only mediator of the hypoxia-induced cell cycle block seen in all cells and all cell cycle phases. Moreover, the cell cycle-dependent induction of p53 by hypoxia suggests that the primary function of p53 accumulation during hypoxia is other than to arrest the cells.

Two novel missense mutations in the LDL receptor gene causing familial hypercholesterolemia

We have employed analysis of single-strand conformation polymorphisms to identify mutations in the low density lipoprotein receptor gene causing familial hypercholesterolemia. Two familial hypercholesterolemia heterozygotes had abnormal single-strand conformation polymorphism patterns of exons 4 and 8. DNA sequencing revealed that the abnormal pattern of exon 4 was due to heterozygosity (G/T) at nucleotide 502. Nucleotide 502 is the first base of codon 147, and the G->T mutation (D147Y) changes this codon from AspGAC to TyrUAC. The abnormal pattern of exon 8 was due to heterozygosity (A/G) at nucleotide 1097. Nucleotide 1097 is the second base of codon 345, and the A->G mutation (Q345R) changes this codon from GlnCAG to ArgCGG. Based upon screening of 437 unrelated familial hypercholesterolemia heterozygotes, both D147Y and Q345R account for about 0.5% of the mutations causing familial hypercholesterolemia in Norway.

Two novel point mutations in the EGF precursor homology domain of the LDL receptor gene causing familial hypercholesterolemia

Familial hypercholesterolemia is caused by mutations in the low density lipoprotein (LDL) receptor gene. Analysis of single-strand conformation polymorphisms of exons 10 and 11 of the LDL receptor gene from familial hypercholesterolemia heterozygotes indicated the presence of two mutations, which were characterized by DNA sequencing. One mutation (delta N466) was a 3-bp deletion in exon 10 that deletes Asn in codon 466. The other (intron 11 +1, G-->T) was a splice donor mutation at position +1 of intron 11.

Screening for known mutations in the LDL receptor gene causing familial hypercholesterolemia

Familial hypercholesterolemia (FH) is caused by defective low density lipoprotein (LDL) receptors and is characterized by hypercholesterolemia and premature coronary heart disease. Two strategies can be used to identify the mutation in the LDL receptor gene underlying FH. One strategy is to search for novel mutations by DNA sequencing with or without prior mutation screening. The other strategy is to screen for known mutations. In this study we employed the latter strategy to screen 75 unrelated, Norwegian FH subjects for 38 known mutations. Three of the 38 mutations were detected in our group of FH subjects. Two subjects had FH-Padova, one had FH-Cincinnati-2 and one had FH-Gujerat. When additional unrelated FH heterozygotes were screened for the three mutations, the gene frequencies were 1.3%, 1.0% and 3.0%, respectively. In addition to identifying known mutations we also detected a novel stop codon in codon 541 (S541X). We conclude that screening for known mutations in the LDL receptor gene should be used as a complementary strategy to screening for novel mutations in order to understand the molecular genetics of FH.

Two founder mutations in the LDL receptor gene in Norwegian familial hypercholesterolemia subjects

DNA from 20 unrelated familial hypercholesterolemia (FH) subjects were studied by analysis of single-strand conformation polymorphisms (SSCP) for mutations in exon 3 of the low density lipoprotein (LDL) receptor gene. Four different SSCP patterns were observed. The underlying mutations were characterized by DNA sequencing. One pattern represented the wild-type sequence. Another pattern represented a C-->G mutation (FH-Svartor) that changes codon 78 into the amber stop codon. The two other patterns represented heterozygosity and homozygosity, respectively, for a G-->A splice donor mutation (FH-Elverum) in intron 3. Based upon two PCR-based assays, the frequencies of FH-Svartor and FH-Elverum among 267 unrelated FH subjects, were 8% and 25%, respectively. FH Svartor was located on a chromosome with haplotype 3 in all five families where haplotype analysis were performed. FH Elverum was located on haplotype 2 in 16 out of 20 families. The two mutations must be considered founder mutations in the Norwegian population, and their existence will be clinically useful in diagnosing FH. The presence of two founder mutations together with previously published data on the prevalence of FH in Norway, indicate that FH may be a more common disease in Norway than previously thought.

Familial hypercholesterolaemia caused by a non-sense mutation in codon 329 of the LDL receptor gene

Analysis of single-strand conformation polymorphisms (SSCP) was employed to screen familial hypercholesterolaemia (FH) subjects for point mutations in exon 7 of the low density lipoprotein receptor (LDLR) gene. An abnormal band pattern was found in one out of 100 unrelated FH subjects. The underlying mutation was found by DNA sequencing to be due to heterozygosity (C/T) at nucleotide 1048. Nucleotide 1048 is the first nucleotide of codon 329, and is located within the domain that has a high degree of homology with the precursor for epidermal growth factor. The C-->T transition, referred to as FH-Fossum, changes codon 329 from CGAArg to TGAStop. The mutation is expected to cause a class 1 receptor defect.

Evaluation of running conditions for SSCP analysis: application of SSCP for detection of point mutations in the LDL receptor gene

We have performed analyses of single-strand conformation polymorphisms (SSCP) of the promoter region and the translated parts of the 18 exons of the low-density lipoprotein receptor (LDLR) gene. DNA from 20 unrelated familial hypercholesterolemia (FH) patients was studied. Four different running conditions were used for the nondenaturing gel electrophoresis to systematically evaluate how differences in the running conditions affect the sensitivity of the assay. These conditions were 15 W, 40 W, and 50 W in the absence of glycerol, and 50 W in the presence of 10% glycerol. SSCP analyses of the 18 PCR fragments for the 20 subjects revealed a total of 46 genotypes at 15 W, 45 at 50 W, 42 at 40 W, and 41 at 50 W with 10% glycerol. A total of 53 different genotypes were observed when the results of the four conditions were considered together. Assuming that the four conditions together detected 100% of the different genotypes, the sensitivity of the four individual conditions ranged between 87% (15 W) and 77% (50 W with 10% glycerol). There were marked differences among the different running conditions to detect abnormal SSCP patterns of individual exons. Therefore, different conditions should be used for the different exons of the LDLR gene.

Screening for point mutations in exon 10 of the low density lipoprotein receptor gene by analysis of single-strand conformation polymorphisms: detection of a nonsense mutation-FH469-->Stop

DNA from 40 unrelated familial hypercholesterolemia (FH) heterozygotes were subjected to analyses of single-strand conformation polymorphisms (SSCPs) of exon 10 of the low density lipoprotein receptor (LDLR) gene. Four different SSCP patterns were observed. The underlying mutations were characterized by DNA sequencing. Three of the patterns represented the three genotypes of a recently described sense mutation in codon 450. A method based upon the polymerase chain reaction (PCR) was developed to analyze this mutation. The frequencies of the wild-type (G at nucleotide 1413) and mutant (A at nucleotide 1413) alleles were 0.56 and 0.44, respectively. The fourth pattern was found in only one FH heterozygote and was caused by heterozygosity at nucleotide 1469 (G/A). Nucleotide 1469 is the second base of codon 469Trp(TGG). The G-->A mutation changes this codon into the amber stop codon, and is referred to as FH469-->Stop. The mutant receptor consists of the amino terminal 468 amino acids. Because the truncated receptor has lost the membrane-spanning domain, it will not be anchored in the cell membrane. FH469-->Stop destroys an AvaII restriction site, and this characteristic was used to develop a PCR method to establish its frequency in Norwegian FH subjects. Two out of 204 (1%) unrelated FH heterozygotes possessed the mutation.

Screening for point mutations by semi-automated DNA sequencing using sequenase and magnetic beads

We have established an improved method for detecting point mutations by semi-automated DNA sequencing of PCR fragments generated from genomic DNA. The method employs magnetic beads to create immobilized single-stranded DNA templates, and the sequencing reaction is performed with Sequenase. This method is superior to sequencing with Taq DNA polymerase because the uniform peak height with Sequenase makes heterozygosity easily detectable as double peaks that are half the normal height. Detection of heterozygosity by this method is illustrated by sequencing a 180-bp fragment of the human apolipoprotein B gene. This fragment contains codon 3500, where a point mutation (3500CGG-->CAG) is found in subjects with the autosomal dominant disease familial defective apolipoprotein B. The nonuniform peak height with Taq DNA polymerase makes it more difficult to detect heterozygosity. This is also illustrated by sequencing a 278-bp fragment of the low-density lipoprotein receptor gene.

A new polymorphism in exon 11 of the LDL receptor gene in healthy people and in familial hypercholesterolemia subjects

We have screened exon 11 of the low density lipoprotein receptor (LDLR) gene from familial hypercholesterolemia (FH) heterozygotes for point mutations by using analysis of single strand conformation polymorphisms (SSCP). A variant pattern was observed in three out of 39 subjects. By DNA sequencing, this variant pattern was found to be due to a C-->T transition at nucleotide 1617 that affects the third base of codon 518. A PCR method was developed to screen FH heterozygotes and normal subjects for this mutation. The gene frequencies in FH heterozygotes and normal subjects were 4% and 4.5%, respectively. Thus, the mutation cannot be in linkage disequilibrium with a mutation that causes FH. Rather, the mutation may be a useful genetic marker at the LDLR locus. Haplotype analysis at the LDLR locus in two FH families where the proband possessed the mutation revealed that the mutation was on two different haplotypes. This finding is consistent with the mutation occurring at a mutational hot spot.

The effect of caffeine on cell growth and metabolism of thymidine in Escherichia coli

(1) The influence of caffeine on growth and on the metabolism of thymidine was investigated in various E. coli strains. Caffeine caused filamentous growth in all strains investigated. The caffeine effect was reversible. (2) The incorporation of thymidine into DNA was inhibited by caffeine, and the inhibition was most pronounced with bacterial cultures grown overnight in the presence of caffeine before the addition of thymidine. For cells not pretreated with caffeine the inhibitory effect of caffeine decreased with increasing concentrations of thymidine up to about 1 microM whereafter it remained constant. The effect of thymidine concentration on the inhibition was less for bacteria that had grown overnight in the presence of caffeine than for bacteria not pretreated with caffeine. (3) Caffeine inhibited thymidine kinase, but it had no effect on thymidine phosphorylase or thymidine nucleotide kinases. (4) It is suggested that caffeine interferes with uptake of thymidine, conversion of thymidine to dTTP and the DNA synthesis process itself. Filamentous growth could be the result of the inhibition of DNA synthesis.