Analysis of low concentrations of 5-bromo-2-deoxyuridine on sister chromatid exchanges in human lymphocytes

To determine a concentration of 5-bromo-2-deoxyuridine (BrdU) sufficient for sister chromatid differentiation (SCD), and yet having a minimal effect on the number of sister chromatid exchanges (SCEs), we assessed the effect produced on the number of SCEs by low concentrations (1, 3, and 10 micrograms/mL) of BrdU. SCD was not obtained in 19% of the 31 subjects with 1 microgram/mL of BrdU, while the differentiation was adequate for all samples treated with 3 and 10 micrograms/mL. We statistically analysed the effects of these three different doses and found no significant difference in the number of SCEs obtained with the doses of 1 and 3 micrograms/mL, but a significant difference was observed between these two concentrations and 10 micrograms/mL. We therefore suggest that the dose of 3 micrograms/mL, while sufficient to produce reliable differential staining, still permits an adequate evaluation of the base line of SCEs and appears to enhance the sensitivity of the test to evaluate between-individual variations. Our experiments also underline that SCE counts should include the centromere exchanges.     

Metabolism of progesterone by preimplantation mouse blastocysts in culture

This study examined the question whether or not preimplantation mouse blastocysts can metabolize progesterone (P). When young (Day 4) and implanting (Day 5) blastocysts were cultured in supplemented Eagle's minimum essential medium containing 0.4 microM [3H]P, metabolism of P and formation of metabolites were noticed at 10 h of culture. The metabolites accumulated in medium as the culture continued to 118 h. Three of the four metabolite fractions were identified, by crystallization to constant sp. act., to be 5 alpha-pregnane-3,20-dione and 3 beta-hydroxy-5 alpha-pregnan-20-one (or allopregnanolone), accounting for 22 and 57% of radioactivity, respectively, and a small amount (1-10%) of 3 alpha-hydroxy-5 alpha-pregnan-20-one. This suggests that both delta 4-5 alpha-reductase and 3 alpha- and 3 beta-hydroxysteroid dehydrogenase are active. Day 5 blastocysts were much more active than Day 4 blastocysts in P metabolism. It is suggested that the ability of blastocysts to metabolize P could produce the following effects in the adjacent endometrium: a lessening of P effects; and consequently a change in P-estrogen interaction; and possible effects from the metabolites. These local effects of embryos on the endometrium may be important for embryonic development and implantation.     

Gene mapping on maize pachytene chromosomes by in situ hybridization

A sensitive in situ hybridization technique which was effective for mapping genes of low copy number on human metaphase chromosomes was used for gene mapping on maize pachytene chromosomes. A cloned genomic EcoR1 fragment of 10.8 kb, containing most or all of the sequence encoding the Waxy locus mRNA, was used as the probe. Southern DNA blotting analyses performed by Shure et al. (1983) indicated that the Waxy locus was a single copy sequence. In our in situ hybridization experiment, the probe hybridized to a specific site on chromosome 9. Labeling at this site was detected in 48.6% of 154 randomly selected copies of chromosome 9. To test the sensitivity of the method, subclones of the fragment with insert sizes of 6.6, 4.7, 3.5, 2.3, 1.9 and 0.8 kb were used for in situ hybridizations. Labeling efficiency for each probe was determined. The data showed that a single copy probe of 1.9 kb could be detected at the correct position in 18% of 183 randomly selected number 9 chromosomes.     

Contractility, ATP, and creatine phosphate during myocardial ischaemia and reperfusion: the effects of adenosine and inhibition of adenosine catabolism in the dog heart

Provision of AMP or adenosine to heart cells during recovery from episodes of myocardial ischaemia accelerates physiological, biochemical, and structural recovery. Inhibition of adenosine loss from the tissue during ischaemia should have a similar effect. This hypothesis was tested in dog heart by infusion of adenosine and inhibitors of adenosine catabolism prior to, during, and following ischaemia. Post-ischaemic recovery of ATP and contractile function was accelerated significantly by adenosine and by inhibitors of adenosine catabolism both singly and in combination. Contractility and ATP levels during ischaemia were also increased by these inhibitors.     

Joint report of the Third International Bovine Lymphocyte Antigen (BoLA) Workshop, Helsinki, Finland, 27 July 1986

Two hundred and eighty-two alloantisera were submitted by 20 participating laboratories from 13 countries and tested against lymphocytes of 1298 cattle. The cell panel consisted of samples from 38 Bos taurus breeds, 11 Bos taurus crossbreeds, 4 Bos indicus breeds, 6 Bos taurus x Bos indicus, and a variety of other crossbred populations. Using a standardized lymphocytotoxicity test, all 17 previously identified BoLA specificities were confirmed. The workshop produced agreement on 16 new lymphocyte alloantigenic specificities. Three of the new specificities behaved as splits of previously identified BoLA specificities. Four of the new specificities behaved as alleles at the agreed BoLA-A locus. Seven new specificities are tentatively assigned to the BoLA-A locus but require further definition. Two new specificities may represent products of a second closely-linked BoLA locus.     

云南呈贡梁王山现代花粉雨的研究

本文通过对云南呈贡梁王山5块表土分析,初步研究了主要植物花粉的百分含量与其植物覆盖率之间的数量关系,并用校正系数R值表示。按照R值的大小,分为两组:R>1属于超代表性,包括有松、桤木、马桑、蒿和部分蕨类植物;R<1属于低代表性,包括有油杉、栲和石栎、滇青冈、栎、铁仔。在分析松粉分布特征基础上,认为昆明地区西风急流对松粉的传播是主要因素。     

Effects of chloroquine on the torsional dynamics and rigidities of linear and supercoiled DNAs at low ionic strength

The magnitude and uniformity of the torsion elastic constant (alpha) of linear and supercoiled pBR322 DNAs are measured in 3 mM Tris as a function of added chloroquine/basepair ratio (chl/bp) by studying the fluorescence polarization anisotropy of intercalated ethidium dye. The time-resolved FPA is measured using a picosecond dye-laser for excitation and time-correlated single-photon counting detection. For both linear and supercoiled DNAs, alpha remains uniform except at the very highest chl/bp ratio examined. For the linear DNA, alpha decreases from 5.0 x 10(-12) dyne-cm at chl/bp = 0 to about 3.5 x 10(-12) dyne-cm at chl/bp = 0.5, and remains at that value up to chl/bp = 5, whereupon it increases back up to its original value. For the supercoiled DNA, alpha remains constant at about 5.2 x 10(-12) dyne-cm from chl/bp = 0 up to chl/bp = 5, whereupon it increases in parallel with the linear DNA. The effect of chloroquine on the secondary structure, torsion constant, and torsional dynamics evidently differs substantially between linear and supercoiled DNAs, even under conditions where the supercoiled DNA is completely relaxed and both DNAs bind the same amount of dye. This strongly contradicts any notion that the local structures of linear and relaxed supercoiled DNA/dye complexes with the same binding ratio are identical. The increase in apparent alpha at chl/bp = 5 for both DNAs may be due to stacking of the chloroquine in the major groove and consequent stiffening of the filament.