HBV-DNA与乙型肝炎血清标志物的相关性分析

目的：探讨乙型肝炎病毒（HBV）DNA载量与其血清标志物的相关性。方法：运用荧光定量聚合酶链反应（FQ-PCR）、酶联免疫吸附实验（ELISA）分别检测503例患者HBV．DNA载量和HBV血清标志物。根据HBV血清标志物结果分为大三阳组、小三阳组、少见模式组、抗体阳性及全阴组,比较各组间HBV—DNA的阳性率及定量值。结果：在大三阳组、小三阳组、少见模式组、抗体阳性及全阴组HBV—DNA的阳性率分别为90％、65．1％、65．2％、2．0％,HBV—DNA的定量结果（10gHBV—DNA）别为6．32±1．96、2．01±1．68、3．48＋2．52f抗体阳性及全阴组阳性例数过低,不纳入统计）。大三阳组HBV—DNA的阳性率显著高于小三阳组（P〈0．05）。大三阳组、小三阳组HBV—DNA的阳性率与少见模式组比较,差异均无统计学意义（P〉0．05）,但大三阳组、小三阳组、少见模式组HBV．DNA的阳性率均显著高于抗体阳性及全阴组（P〈0．01）。HBsAg、HBeAg阳性组HBV—DNA的阳性率分别显著高于HB—sAg、HBeAg阴性组（P〈0．01）。小三阳组、少见模式组HBV．DNA载量均显著低于大三阳组（P〈0．01）,少见模式组HBV—DNA载量显著高于小三阳组（P〈0．05）。结论：HBV—DNA的阳性率与HBeAg、HBsAg相关;HBV—DNA栽量与HBV血清标志物模式相关。     

Cr^3＋胁迫对苦草叶片活性氧清除系统和叶细胞超微结构的影响

研究了不同浓度Cr^3＋胁迫对苦草[Vallisneria natarts（Lour．）Hara]叶片活性氧清除系统及细胞超微结构的影响。结果表明,随Cr^3＋浓度的提高（0．5-15．0mg·L^-1）,苦草叶片中O2^-·和MDA含量、SOD和POD及CAT活性均呈现先上升后显著下降的变化趋势,且在10．0和15．0mg·L^-1 Cr^3＋胁迫条件下显著低于对照（P〈0．05）。在1．0mg·L^-1Cr^3＋胁迫条件下,O2^-·的含量达到最高（0．96 OD·g^-2）;在2．0mg·L^-1Cr^3＋胁迫条件下,MDA含量和SOD、POD及CAT活性最高。随Cr^3＋胁迫浓度的提高,苦草叶片细胞超微结构受损程度逐渐加深,导致核仁和高尔基体消失;线粒体脊突膨胀,线粒体膜受损并出现囊泡状结构;叶绿体变形、类囊体膨胀受损并最终导致叶绿体破损。表明高浓度Cr^3＋胁迫对苦草叶片细胞产生了不可逆的伤害。     

关于链格孢的毒性及其产毒条件的研究

本文报告了从食管癌高发区林县分离的具有强烈毒性和致突变性的链格孢(Alternariaalternata)“D_(10)-A_2”菌株粗提物半数致死量的测定,结果为71.25g 培养物/kg 体重;7个菌株粗提物的程序外 DNA 合成(UDS)试验,6个菌株粗提物的 DNA 合成抑制(DSI)试验。结果 UDS 试验6个菌株为阳性,DSI 试验5个菌株为阳性。说明互隔交链孢提取物可致人体细胞 DNA 的损伤。本文还报道了链格孢适宜的产毒条件。链格孢在一般粮食上均能生长繁殖产毒,适温为25℃,适宜的湿度根据粮食品种不同而为33—50％含水量。在北方侵染的主要粮食为小麦,当麦粒灌浆成熟期遇到较长时间的阴雨天气,或在收割脱粒时遇到连阴雨,麦粒被雨水浸泡。污染非发生于贮存期。     

人参皂苷Rb1、Rc对大鼠胚胎脑发育及GPx基因表达的影响

目的观察人参皂苷Rb1、Rc对sD大鼠胚胎脑发育及谷胱甘肽过氧化物酶（61utathione peroxidase,GPx）基因表达的影响。方法实验选用全胚胎体外培养方法,根据Van Maele-Fabry等制定的形态学分析系统进行形态学检测,实验随机分为对照组、人参皂苷Rbl（10,45和90ug／ml）组和人参皂苷Rc（10,45和90ug／ml）组,采用半定量RT—PCR分析人参皂苷Rb1和人参皂苷Rc对胚胎谷胱甘肽过氧化物酶基因表达的影响。结果与对照组比较,人参皂苷Rb1（10,45和90ug／ml）组胚胎脑、前脑、中脑与后脑的长度值没有统计学意义（P〉0．05）;与对照组比较,人参皂苷Rc（10,45和90ug／m1）组前脑、中脑与后脑的长度值显著增加（P〈0．05）。RT—PCR结果显示,人参皂苷Rb1（10,45和90ug／ml）组cGPx与phGPx mRNA的表达水平与对照组比较均没有统计学意义（P〉O．05）,而pGPxmRNA的表达水平在浓度50和100ug／ml时显著增加（P〈0．05）。人参皂苷Rc（10,45和90ug／ml）组cGPx与phGPxmRNA的表达水平与对照组比较均没有统计学意义（P〉0．05）,而pGPxmRNA的表达水平在各种浓度的Rc作用后都增加,且在溶度10和45ug／ml浓度时增加显著（P〈0．05）。结论一定剂量的人参皂苷Rc能促进胚胎脑的发育,一定剂量的人参皂苷Rb1、Rc能明显增强胚胎脑pGPx mRNA的表达水平。     

应用改良彗星试验检测杀虫剂对小鼠细胞DNA的损伤

目的：检测杀虫剂（杀灭菊酯乳油）是否对小鼠外周血淋巴细胞DNA有损伤。方法：应用改良彗星试验（单细胞凝胶电泳）分别检测三个剂量组和对照组小鼠外周血淋巴细胞。结果：剂量组的彗星出现率与阴性对照组存在显著差异（P＜0．05）,而与阳性对照组差异不显著（P＞0．05）。结论：该杀虫剂对小鼠外周血淋巴细胞DNA有一定程度的损伤。     

六价铬对水绵生长的毒性效应

为研究六价铬（Cr^6＋）对水绵（Spirogyrasp．）的毒性效应和水绵对六价铬的毒性响应,实验设置5个暴露组（4、6、8、10和12mg／L）和1个对照组。结果表明：96h后各暴露组对水绵的生长均有抑制作用,铬浓度越高,藻细胞叶绿素a越低,显示出较明显的剂量一效应关系;六价铬对水绵的96h的Ec。值为7．25mg／L。细胞浸出液电导率在低浓度（4～6mg／L）组上升较缓慢,在高浓度组（8～12mg／L）上升显著;丙二醛（MDA）累积含量在Cr6＋≥4mg／L时,累计含量上升较高（P〈0．01）,当Cr^6＋≥8mg／L时,累积含量上升较少。水绵细胞浸出液电导率与MDA存在显著正相关（P〈0．05,r=0．891）。水绵细胞浸出液电导率和MDA含量与六价铬浓度分别存在显著（P〈0．05,r=0．951）和极显著（P〈0．01,r=0．977）的非线性的毒性响应关系。     

绿巨人茎尖的离体培养及快速繁殖

1植物名称绿巨人（SpathiphyllumKochii）。2材料类别带顶芽茎段经表面消毒后从顶端分离出的2mm茎尖。3培养条件培养基：（1）1／2MS＋6－BA0．1mg·L－1（单位下同）＋IAA0．3;（2）MS＋6－BA0．5＋NAA0．5;（3）1／2MS＋6－BA0．1＋IBA0．5。以上培养基均含3％蔗糖、0．8％琼脂,pH5．8。培养温度28～30℃,照光12h·d－1,光照度2000lx。4生长与分化情况4．1茎尖的制备与培养从盆栽的生长旺盛、粗壮无病虫害的绿巨人植株上切取4cm带顶芽的茎段,除去叶片和大部分叶柄后,置烧杯中,加入1滴中性洗涤液及少量自来水,用细软的…     

循环DNA和HBV—DNA载量与原发性肝癌的相关性探讨

目的：探讨血浆DNA和HBV—DNA载量在病毒性肝炎肝硬化后原发性肝癌（PHC）的诊断价值。方法：用RT—PCR方法随访检测HBsAg阳性且经彩色B超诊断为肝硬化的患者,每6个月检测一次患者的血液循环DNA和HBV-DNA载量,直到经临床症状、彩色B超、CT诊断为原发性肝癌为止。结果：在PHC中,循环DNA61．3±31．9ng／ml,健康对照组20．3±9．9ng／ml,两组差异显著（P〈0．01）;而HBV—DNA载量,在PHC确诊时多数处于较低水平,78％≤105copies／ml,与PHC确诊前有明显差异（P〈0．01）。PHC未发生淋巴结转移者循环DNA51．2±17．9ng／ml,淋巴结转移者循环DNA73．9±23．7ng／ml,两者存在差异（P〈0．05）;而HBV-DNA载量有无淋巴结转移无明显差异。结论：联合检测血液循环DNA和HBV—DNA载量对PHC的预测、预后价值明显,且方法简单,易于开展。     

系统性红斑狼疮患者外周血调节性T细胞、Foxp3和IL-6的表达

目的探讨系统性红斑狼疮（ systemic lupus erythematosus, SLE）患者外周血CD4^＋ CD25^＋调节性T细胞（regulatory T cells,Tregs）、roxp3 mRNA和血浆IL-6表达的意义。方法对38例SLE患者和16例正常人采用流式细胞术检测外周血CD4^＋ CD25^＋ T regs百分率,RT-PCR检测roxp3 mRNA表达,ELISA法检测IL-6水平。结果①SLE活动组和非活动组的CD4^＋ CD25^＋ Tregs水平均显著低于正常对照组（P〈0．01）;②SLE活动组的roxp3 mRNA表达水平明显低于正常对照组（P〈0．05）;③SLE活动组和非活动组血浆的IL-6水平均显著高于正常对照组（P〈0．01）,而且活动组显著高于非活动组（P〈0．05）;④38例SLE患者的CD4^＋ CD25^＋Tregs水平与SLEDAI评分呈显著性负相关（P〈0．01）,F0xp3mRNA水平与CD4^＋ CD25^＋Tregs呈显著性正相关（P〈0．01）,血浆IL-6水平与SLEDAI评分之间呈显著性正相关（P〈0．01）,血浆IL-6水平与CD4^＋ CD25^＋Tregs／CD4^＋细胞比值呈显著负相关（P〈0．05）。结论CD4^＋ CD25^＋Tregs和Foxp3以及IL-6可能在SLE的发生和发展中发挥重要作用。     

不同临床类型乙型病毒感染者外周血T细胞亚群与血清HBVDNA载量及HBeAg滴度相关性分析

目的：探讨慢性乙型肝炎病毒（HBV）感染患者外周血T细胞亚群与血清HBVDNA载量及HbeAg滴度的关系。方法：选取103名HBV感染患者和20名健康者为研究对象。流式细胞术检测外周血T细胞亚群,聚合酶链式反应及酶免疫分析法分别检测血清HBVDNA载量及HbeAg滴度。结果：慢性乙型肝炎患者和慢性HBV携带者外周血CD3可、CD4T淋巴细胞亚群百分数低于健康对照组,结果有统计学意义（P〈0．05或0．01;而CD8＋T细胞亚群则呈现相反趋势,结果亦有统计学意义（P〈0．05或0．01）。HBeAg阴性组中,HBVDNA水平与CD8T细胞亚群百分数呈正相关（r=0．567,P〈0．01）,与CD47CD8＋T细胞亚群百分数比值呈负相关（r=-0．601,P〈0．01）,而与CD3＋T、CD4＋T细胞亚群百分数无相关性。HBeAg阳性组中,HBVDNA水平及HbeAg滴度与cD3＋1r、cD41、CD8叮细胞百分数及CD47CD8＋T细胞百分数均无相关性（P〉0．05）。结论：不同临床类型的慢性乙型肝炎病毒感染患者外周血T细胞亚群存在不同程度细胞免疫功能降低和细胞免疫调节异常。HbeAg阴性的HBV感染患者,其血清HBVDNA水平与外周血T淋巴细胞免疫存在相关性。     

Cr6+、Cr3+胁迫对黑藻生理生化影响的比较研究

以沉水植物黑藻 (Hydrillaverticillata(L .f.)Royle)为实验材料 ,通过模拟水体Cr6+ 、Cr3 + 污染环境 ,比较研究了两种价态铬对黑藻叶的毒害影响。结果表明 :随着Cr6+ 、Cr3 + 浓度的加大 ,超氧阴离子 (O 2)产生速率、丙二醛 (MDA)、可溶性蛋白含量皆呈先升后降趋势。Cr6+ 、Cr3 + 浓度过高时 ,三种抗氧化酶 (SOD、POD、CAT)活性比例失衡 ,且Cr6+ 处理组的O 2 产生速率、MDA含量高于Cr3 + 处理组 ,叶绿素、可溶性蛋白含量、叶绿素a/b值低于Cr3 + 处理组 ,显示出Cr6+ 的毒性远大于Cr3 + 。     

Cr6+胁迫对小麦幼苗根系生长的影响及DNA损伤效应研究

研究了Cr6+胁迫对3 d和10 d龄小麦幼苗根系生长的影响及DNA损伤效应.结果表明(1)>5 mg/L的Cr6+均显著或极显著降低幼苗根长、根数及根系鲜重、干重,3 d龄幼苗根系生长比10 d龄幼苗对Cr6+胁迫更敏感;(2)所试浓度Cr6+均降低两苗龄幼苗根系DNA含量;5～20 mg/L Cr6+浓度范围内,3 d龄幼苗根系DNA含量下降幅度大于10 d龄幼苗,Cr6+浓度>20 mg/L时,3 d龄幼苗根系DNA含量低于10 d龄幼苗;(3)Cr6+对两苗龄幼苗根系DNA增色效应的影响均呈现随浓度增大先升高后下降的趋势;3 d龄幼苗根系DNA增色效应在5～60 mg/L Cr6+浓度范围内大于对照,Cr6+浓度>60 mg/L时则小于对照;在所试Cr6+浓度范围内,10 d龄幼苗根系DNA增色效应均大于对照.     

甘蔗渣接枝四乙烯五胺制备治理印染废水的新型吸附剂

论文通过在甘蔗渣(sugarcane bagasse,SB)中引入四乙烯五胺获得改性甘蔗渣(modified sugarcane bagasse,MSB),制备出对有机染料伊红和重金属离子Cu²⁺、Cr³⁺均有较好吸附能力的吸附剂,并研究了pH、温度、初始浓度等因素对吸附的影响.结果表明当伊红溶液pH为6时,MSB的吸附量比SB提高了18倍,对金属Cu²⁺ 、Cr³⁺的吸附量也大大高于SB.染料伊红的吸附过程可以用Langmuir 型吸附等温线较好地模拟,由方程可得25℃下伊红的最大吸附量为399.04 mg·g^-1,MSB对伊红的吸附行为符合伪二级吸附动力学模型.实验结果显示改性甘蔗渣(modified sugarcane bagasse,MSB)是一种吸附性能优异的吸附剂,用于处理印染废水与制革废水有较好的应用前景.     

Ticarcillin administration to the equine: Intrauterine and intramuscular

Serum levels of ticarcillin disodium, a semi-synthetic penicillin (Beecham Laboratories, Bristol, Tennessee, 37620), were measured at various time intervals up to and including 24 h after intrauterine and intramuscular administration in adult female horses. Three separate studies were conducted in Part I: in the first and second studies, serum levels were measured after intrauterine administration of 1 and 3 g of ticarcillin, respectively, and in the third study, levels were measured after intramuscular administration of 6 g of ticarcillin. In Part II, serum levels of ticarcillin were measured after intramuscular administration of ticarcillin at dosages based on body weight: 10 mg/lb (22 mg/kg) of body weight, 15 mg/lb (33 mg/kg) of body weight and 20 mg/lb (44 mg/kg) of body weight. Results showed little if any absorption of the antibiotics into the systemic circulation after intrauterine administration. All serum levels measured after administration of both intrauterine dosages of 1 and 3 g were less than 4.0 ug/ml. Peak serum concentrations, after intramuscular administration of 6 g of ticarcillin, occurred between 20 and 45 min after administration and averaged 15.97 +/- 5.0 ug/ml. Average peak serum concentrations, after intramuscular administration of 10 mg/lb (22 mg/kg) of body weight, 15 mg/lb (33 mg/kg) of body weight, 15 mg/lb (33 mg/kg) and 20 mg/lb (44 mg/kg) of body weight, were 16.12 ug/ml, 25.75 ug/ml and 50.25 ug/ml, respectively. After intramuscular administration of 6 g of ticaracilin, average serum half-life was determined to be 2.9 h.     

Arginase as one of the inhibitory principles in the density-dependent as well as plasma membrane-mediated inhibition of liver cell growth in vitro

Liver cells isolated from the adult rat livers under mild conditions were preincubated for 1 day with Williams medium E (WE) containing serum, dexamethasone and insulin, and then the cells (monolayered) were incubated for 2-3 days with WE (1 ml) containing only insulin to measure DNA synthesis and/or mitosis. DNA synthesis of cultured liver cells was dependent on cell densities within a region from 0.1 X 10(6) to 1.0 X 10(6) nuclei/dish (Falcon, diameter 35 mm). The addition of EGF from the beginning of preincubation stimulated DNA synthesis (or replication) as well as cell proliferation in vitro, but the density-dependent inhibition of DNA synthesis was observed similarly in the presence of EGF. In contrast to the low and high density cultures, DNA synthesis in the intermediary density cultures was enhanced by enlarging the medium volume or by adding ornithine (arginase inhibitor). DNA synthesis in low density cultures was inhibited by liver plasma membranes in a concentration-dependent fashion. The inhibition of DNA synthesis by liver plasma membranes in low concentrations (less than 30 micrograms protein/ml) was reduced by adding either extra arginine or ornithine. DNA synthesis of cultured liver cells (low density) was inhibited by replacing arginine in WE with equimolar ornithine and urea or by adding a commercial arginase (bovine liver). These, together with earlier findings indicating the presence of arginase in liver plasma membranes (outer leaflet), seem to support the idea that arginase may be involved in density-dependent as well as plasma membrane-mediated inhibition of DNA synthesis of cultured liver cells. However, this does not exclude possible involvement of other inhibitory principle(s), such as direct cell-to-cell or cell-to-plasma membrane interactions, especially in higher cell densities or larger plasma membrane concentrations.     

Hexaamminecobalt(III) binding environments on double-helical DNA.

Previous cation nmr evidence suggests that univalent cations such as Na+ bind to DNA in a diffuse, nonspecific manner, whereas di- and trivalent cations show distinct binding heterogeneity. Here are reported 59Co- and 23Na-nmr measurements of the %GC dependence of the DNA binding behavior of the trivalent hexaamminecobalt(III) cation. When Co(NH3)6Cl3 titrations are performed on one mammalian and three bacterial DNAs, evidence is found for at least three distinct classes of bound Co(NH3)6(3+). A comparison of titration curves for all four DNAs demonstrates that an increase in GC content correlates with an increase in the fraction of specific Co(NH3)6(3+). binding sites. For M. lysodeikticus DNA (72% GC), a slowly exchanging class of bound 59Co(NH3)6(3+) is apparent. This class of sites is saturated at very low binding densities (between 0.02 and 0.03 cobalt cations per DNA phosphate). At higher binding densities (greater than 0.03), the signal due to slowly exchanging 59Co(NH3)6(3+) disappears into the noise, and a single 59Co(NH3)6(3+) signal is observed. Within the sensitivity limitations of these measurements, no evidence for slowly exchanging bound 59Co(NH3)6(3+) could be found for any of the other DNAs, for which a single, rapidly exchanging 59Co(NH3)6(3+) signal is observed at all binding densities. For this rapidly exchanging signal, for all four DNAs, the measured 59Co(NH3)6(3+) nmr parameters depend significantly on (a) binding density and (b) GC content of the DNA.(ABSTRACT TRUNCATED AT 250 WORDS)     

Stimulation of DNA synthesis in human fibroblasts by a human nonsuppressible insulin-like protein (NSILP).

When nonsuppressible insulin-like protein (NSILP) isolated and purified from human serum was added at concentrations of 5 and 50 ug/ml to cultures of human dermal fibroblasts, both cell proliferation and DNA synthesis were enhanced. However, NSILP, 50 ug/ml, had no effect on glucose uptake. In contrast, insulin, 40 ng/ml (1.0 mU/ml), had no effect on cell proliferation or DNA synthesis, but stimulated glucose uptake. These observations suggest that human NSILP may play an important role in tissue repair or growth by enhancing fibroblast proliferation, but not a significant glucoregulatory role.     

Effects of bull and heparin and sperm concentrations on in vitro fertilization of buffalo (Bubalus bubalis ) oocytes matured in vitro

A study was undertaken to assess the ability of spermatozoa from 6 buffalo bulls, at different levels of heparin and sperm concentrations, to achieve an acceptable level of fertilization in vitro. Frozen-thawed spermatozoa, 3 dosages of heparin (0, 10 and 100 ug/ml) in the presence and absence of penicillamine, hypotaurine and epinephrine (PHE), and 4 sperm concentrations (1 x 10(6), 2 x 10(6), 3 x 10(6) and 4 x 10(6) /ml) were studied using 3202 buffalo oocytes. The mean proportions of fertilized oocytes in the group treated with 10 ug/ml of heparin were significantly higher (P<0.05) with the semen of Bulls A, B and C (44.7 to 64.3%) than in medium devoid of heparin. An increase in the dosage of heparin from 10 ug/ml to 100 ug/ml reduced the overall fertilization rate. However, optimal fertilization (30.9%) at 100 ug/ml heparin was observed for semen from Bull D. Bulls E and F yielded the lowest fertilization rate (9.6 and 14.2%, respectively) at the above mentioned heparin dosage. Analysis of sperm density revealed that a concentration of 2 x 10(6) spermatozoa yielded optimal fertilization rates in vitro. Higher sperm concentrations (3 x 10(6) or 4 x 10(6)) resulted in higher oocyte penetration rates but gave rise to polyspermy.     

Structure,function, and aggregation of the zinc-free form of the p53 DNA binding domain

The p53 DNA binding domain (DBD) contains a single bound zinc ion that is essential for activity. Zinc remains bound to wild-type DBD at temperatures below 30 degrees C; however, it rapidly dissociates at physiological temperature. The resulting zinc-free protein (apoDBD) is folded and stable. NMR spectra reveal that the DNA binding surface is altered in the absence of Zn(2+). Fluorescence anisotropy studies show that Zn(2+) removal abolishes site-specific DNA binding activity, although full nonspecific DNA binding affinity is retained. Surprisingly, the majority of tumorigenic mutations that destabilize DBD do not appreciably destabilize apoDBD. The R175H mutation instead substantially accelerates the rate of Zn(2+) loss. A considerable fraction of cellular p53 may therefore exist in the folded zinc-free form, especially when tumorigenic mutations are present. ApoDBD appears to promote aggregation of zinc-bound DBD via a nucleation-growth process. These data provide an explanation for the dominant negative phenotype exhibited by many mutations. Through a combination of induced p53 aggregation and diminished site-specific DNA binding activity, Zn(2+) loss may represent a significant inactivation pathway for p53 in the cell.     

Extraction, partial purification and properties of obelin, the calcium-activated luminescent protein from the hydroid Obelia geniculata

1. The Ca(2+)-activated luminescent protein obelin was extracted from the hydroid Obelia geniculata. 2. After the addition of a large excess of calcium (greater than 5mm) a peak in the rate of luminescence occurred within 100ms, followed by an exponential decay (k=2.8s(-1)). The obelin activity (light emitted) was measured by the peak height or by the total number of counts recorded on a scalar in the first 10s after addition of Ca(2+). 3. After an overnight extraction in 40mm-EDTA-200mm-Tris-HCl, pH7.0, 7.2x10(11) counts were obtained from 186g of wet hydroids. 4. The stability of the crude extracts was dependent on pH, being optimal at pH7.0. 5. Obelin could be purified threefold with a yield of 69% by selecting the protein precipitated between 60%- and 100%-saturated (NH(4))(2)SO(4). The precipitate could be stored for at least 6 months as a suspension in 40mm-EDTA+saturated (NH(4))(2)SO(4), pH7.0, frozen at -70 degrees C with a recovery of 95-100%. 6. Luminescence was also stimulated by Sr(2+). However, obelin appeared to have a lower affinity for Sr(2+) than for Ca(2+). Mg(2+) inhibited Ca(2+)-activated luminescence. 7. Obelin could be used to assay as little as 50pmol of Ca(2+) in a final volume of 1ml. 8. At pH7.0 in Ca(2+)-EGTA [ethanedioxybis(ethylamine)tetra-acetate] buffers the rate of obelin luminescence was proportional to the square of the free Ca(2+) concentration in the presence and absence of 1 and 10mm-Mg(2+). Over the range 0.1-10mum-Ca(2+) less than 0.03% of the obelin was consumed/s. 9. In order to use obelin to study free ionized Ca(2+) concentrations similar to those found inside cells in the presence of 10mm-Mg(2+) a minimum of 10(8) counts were required. A total of 10(12) counts can be readily extracted from about 200g of wet hydroids. Thus a sufficient quantity of an aequorin-like calcium-activated luminescent protein should now be available to workers in the United Kingdom in order to carry out physiological experiments.