Two specific topoisomerase II inhibitors prevent replication of human cytomegalovirus DNA: an implied role in replication of the viral genome.

In this study, we show that human cytomegalovirus DNA synthesis is inhibited in infected confluent human embryonic lung cells treated with the DNA-intercalative topoisomerase II inhibitor 4-9'-(acridinylamino)methanesulfon-m-anisidide (m-AMSA). Similar inhibitory effects were observed with VM-26, a nonintercalative topoisomerase II inhibitor. This antiviral effect is not attributable to cytotoxic effects per se. Furthermore, m-AMSA appears to have a notably irreversible inhibitory effect on human cytomegalovirus DNA replication. No inhibition of viral DNA synthesis was observed with o-AMSA, a DNA-intercalative isomer of m-AMSA that does not inhibit topoisomerase II.     

Detection of a single-copy gene on plant chromosomes by in situ hybridization

Summary DNA recombinant technology, combined with improvements in hybridization efficiency and quality of chromosome spreads, has made the method of in situ hybridization a reliable tool for gene mapping used by mammalian cytogeneticists to complement other methods. By appropriate alterations of the method, we demonstrate that detection of unique genes can be achieved along plant chromosomes despite some inherent disadvantages of the plant material. Using genomic subclones homologous to 6.6 kb of the single-copy chalcone synthase gene in parsley, we report the first example of chromosomal detection and localization of a unique endogenous gene in plants.     

Effect of Light on Sterol Changes in Medicago sativa

Most vascular plants contain Δ⁵-sterols as the predominant type; however, a few species such as Medicago sativa, have mainly Δ⁷-sterols. The Δ⁷-sterols of alfalfa are isomers of the common Δ⁵-sterols and are generally assumed to be their immediate precursors. Light had a significant influence on the sterol status of M. sativa. High light intensity and a long day favored the accumulation of dihydrospinasterol; a short day and low light intensity, particularly darkness, favored spinasterol accumulation. These data for Δ⁷-sterol plants agree with those reported for Δ⁵-sterol plants; light favors the accumulation of the monounsaturated 29 carbon sterols and darkness favors the accumulation of the diunsaturated sterols. Proposed is a mechanism to explain the effect of light on the accumulation of Δ⁷- and Δ⁵-sterols.     

Differential effects of tetracaine on charge movements and Ca2+ signals in frog skeletal muscle

The effects of tetracaine on charge movements and on antipyrylazo III signals monitoring intracellular delta [Ca2+] were compared in cut frog semitendinosus muscle fibers in a single vaseline gap-voltage clamp. Low tetracaine concentrations (25-40 microM) markedly reduced delta [Ca2+] signals and shifted the rheobase. However, they neither influenced charge movement nor that peak delta [Ca2+] value associated with the contractile threshold. Higher tetracaine concentrations (100-200 microM) partly inhibited charge movements in cut fibers. They separated a steeply voltage-sensitive charge, some of whose features resembled 'q gamma' reported in intact fibers, and whose movement preceded delta [Ca2+] signals at threshold. These findings: (a) directly confirm an earlier suggestion that tetracaine acts on steps in excitation-contraction coupling rather than myofilament activation; (b) show that tetracaine at low concentrations can directly interfere with sarcoplasmic reticular calcium release without modifying charge movement; (c) show that the tetracaine-sensitive charge, first found in intact fibers, also exists in cut fibers; and (d) make it unlikely that tetracaine-sensitive charge transfer is a consequence of Ca2+ release as suggested on earlier occasions.     

Anti-Ig-mediated proliferation of human B cells in the absence of protein kinase C

Cross-linking of surface Ig has been shown to stimulate phosphatidylinositol hydrolysis in murine B cells, leading to increases in [Ca2+]i and activation of protein kinase C (PKC). Preliminary evidence suggests that a similar activation mechanism occurs in human B cells. We wished to examine whether anti-Ig antibody-stimulated human B cell proliferation is as dependent upon the presence of PKC as is anti-Ig-mediated murine B cell proliferation. Using highly purified, small, dense peripheral-blood B lymphocytes from healthy adult donors, we confirmed that PMA, a direct activator of PKC, is a potent mitogen for human B cells that synergizes with anti-mu antibody. Furthermore, we demonstrated that PMA treatment abolishes detectable cellular stores of immunoreactive PKC. However, after such depletion of cellular PKC, anti-mu antibody is still capable of delivering a proliferative signal to human B cells. It is unlikely that this signal occurs solely on the basis of increases in [Ca2+]i, because the calcium ionophore A23187 does not induce a proliferative response in PMA-treated B cells similar in magnitude to that seen with anti-mu. Additionally, the finding that pretreatment of B cells with PMA ablates the ability of anti-Ig antibody to mobilize intracellular and extracellular calcium also suggests that the ability of PMA to enhance anti-Ig mediated stimulation does not depend on elevations of [Ca2+]i induced by anti-Ig. Together, these observations suggest that anti-Ig signaling of human B cells may occur via other pathways in addition to the phosphatidylinositol system of calcium influx and PKC activation.     

Treatment of burn alopecia with tissue expanders in children

During the past 18 months, 60 tissue expanders were utilized in the reconstruction of 42 children with burn alopecia of the scalp not amenable to a single excision and primary closure at the Shriners Burns Institute in Galveston, Texas. The children were grouped according to the degree of alopecia. All patients with defects of 15 percent or less of the total hair-bearing scalp were able to obtain complete closure of their defects with two operations, i.e., one to place the expander and the second to remove the expander and advance the flaps. Some patients with defects up to 40 percent were closed with serial expansion. Patients with even larger defects had a significant reduction in the percentage of alopecia and benefited from re-creation of anterior hairlines. We have encountered a postoperative complication rate of 10 percent. When compared to previous methods of treating burn alopecia, tissue expansion allows a more rapid closure, fewer operations and coincident anesthetics, and decreased total length of hospitalization.     

小麦叶绿体中CTK结合蛋白的结合活性研究

叶绿体中存在着与细胞分裂素(CTK)专一结合的蛋白质。这一蛋白与6-苄氨基嘌呤(6 BA)的亲和力很强,解离常数达3.7×10~(-8)mol/L。最大结合量为10.7 pmol 6 BA/mg蛋白,Seatchard分析表明只有一类结合位点。不同的叶绿体纯化步骤对CTK结合蛋白的活性有不同的影响,分离步骤少而快速的差速离心法可以得到具有较高结合活性的叶绿体。叶绿体经分离纯化后,低温保存时的结合活性较稳定,-20℃以下可以较长期保存。用EDTA预处理叶绿体,不降低CTK结合蛋白对6 BA的结合活性,而用高浓度的NaCl处理,可以使叶绿体结合6BA的能力明显下降。这说明EDTA不能使CTK结合蛋白从叶绿体膜系统表面解离,而高浓度NaCl则有这种可能性。     

用合成的寡核苷酸探针鉴定中国人β-地中海贫血基因突变

用人工合成的六种对β-地中海贫血基因特异的寡核苷酸作为杂交探针,对10例β-地中海贫血病人及其父母的β-珠蛋白基因进行分析,鉴定出六种β-地中海贫血突变:(1)TATA Box-28 A→G;(2)IVS-1n.5 G→C;(3)Codon 17 A→T;(4)codons 41—42—46p;(5)Codons 71—72+A;(6)IVS-2 n.654C→T。本文分析的中国人β-地中海贫血患者中,上述六种突变所占的百分比分别为5％,10％,10％,40％,20％和15％。     

部分氧化的铁钼蛋白的圆二色散谱和电子顺磁共振谱的研究

棕色固氮菌固氮酶FeMo蛋白与过量（5－6个当量）的酸性靛蓝保温30－60分钟后,蛋白中的P－金属原子族全部氧化,然而蛋白中的FeMoCo全都处于还原状态。Na2S2O4使这种部分氧化的FeMo蛋白中的P-ciuster重新不,甲基紫精可加快这种还原,而亚甲蓝等氧化剂则使这种蛋白中的FeMoCo受到氧化,对这种部分氧化的FeMo蛋白分别进行CD还原滴定和测定氧化过程中的EPR／ABS的变化已经得到p-Cluster和FeMoCo的氧化还原当量数目。