Radioprotection of DNA by thiols: relationship between the net charge on a thiol and its ability to protect DNA

Release of free bases from calf thymus DNA upon irradiation in aerated 0.1 mol dm-3NaClO4 at pH 7 has been measured by HPLC and shown to be markedly influenced by the presence of thiols during irradiation. The ability of thiols to protect DNA was shown to depend upon the net charge (Z) at pH 7 in the order WR 1065 (Z = +2) greater than cysteamine (Z = +1) greater than 2-mercaptoethanol (Z = 0) approximately equal to dithiothreitol (Z = 0) greater than GSH (Z = -1) approximately equal to 2-mercaptoethanesulfonic acid (Z = -1) approximately equal to 2-mercaptosuccinate (Z = -2). A similar dependence of protection upon net charge was found for disulfides: cystamine (Z = +2) greater than 2-mercaptoethyl disulfide (Z = 0) greater than GSSG (Z = -2). Protection by WR 1065, but not by 2-mercaptoethanol or GSH, was found to decrease significantly with increasing ionic strength. Protection by WR 1065 and GSH was not markedly dependent upon pH between pH 6 and 8. The results are explained in terms of electrostatic interaction of the thiols with DNA, leading to high concentrations of cations near DNA, which allow them to scavenge hydroxyl radicals and repair DNA radicals effectively and to low concentrations of anionic thiols near DNA, which limit their effectiveness as protectors. Poly(dG,dC) and calf thymus DNA exhibited comparable release of G and C upon changing from 0.1 to 0.7 mol dm-3 MgSO4. Since this change causes poly(dG,dC), but not calf thymus DNA, to undergo a change from the B-form to the Z-form of DNA, both forms must have a comparable susceptibility to radiation-induced base release.

A randomized comparative clinical evaluation of the Steel Ring, the VCu200 and the TCu220c IUDs

A randomized comparative clinical study of the Steel Ring, VCu200 and TCu220c IUDs was carried out in Beijing. Six-hundred subjects were recruited and each group of 200 was inserted with one of the three devices. The TCu220c and the VCu200 had statistically significantly lower pregnancy and expulsion rates at one and two years of use than the Steel Ring. However, the Steel Ring consistently had the lowest rate of removal for pain and/or bleeding. At two years, the early differences of use-related discontinuation and continuation between the higher rates of the Steel Ring and the lower rates of the VCu200 and TCu220c were significantly reduced. There were no statistically significant differences of net event rates between VCu200 and TCu220c.

[Estrogen receptor (ER) of breast cancer cells. II. Quantitative analysis of breast cancer cells bound with fluoresceinate-ER]

In order to express the quantitative value by the cytochemical method, the breast cancer cells of 41 human and 7 C3H mice were used. The condition of ER was detected by cytochemical (17-fluoresceinated estrone, 17-FE) and biochemical (dextran-coated charcoal, D. C. C.) methods. The relative weight (theta) of each type of cells and the coefficient were obtained by the statistical estimation technique and mathematical modeling. The relative weights of type A, B and C (theta 1, theta 2 and theta 3) were 4.4, 2.8 and 1.8 in human tumor, and 1.9, 0.3 and 1.3 in mouse tumor. The same quantitative unit of value (fmol/mg) can be expressed by the cytochemical method as by the biochemical method. The inadequacies of both methods are presently brought to light. By the D. C. C. method, only about half of the ER in cytosol can be detected and those in the nucleus can not be assayed. By the 17-FE method, it is possible to detect the ER status not only morphologically but also quantitatively.

Colorectal cancer in Chinese and Chinese-Americans

Rationale and plans are described for a collaborative case-control study of large bowel cancer among Chinese-Americans in Los Angeles and the San Francisco Bay Area and among Chinese in Zhejiang Province, People's Republic of China. A common protocol and questionnaire will be used during personal interviews of approximately 400 Chinese and 300 Chinese-American patients with histologically confirmed adenocarcinoma of the colon or rectum and 2,100 Chinese and Chinese-American controls. Controls will be matched to patients on age, sex, and community of residence. The information requested from subjects will permit testing of hypotheses relating colorectal cancer risk to: dietary factors, including intake of fat (saturated and unsaturated), animal protein, fiber, and vitamins A and E and ascorbic acid; physical activity levels and body mass index; reproductive factors among women; history of bowel disease; and family history of cancer. The information requested of Chinese-American subjects will also permit testing of hypotheses relating cancer risk to such migrant factors as United States versus Chinese nativity, duration of residence in the United States, and Chinese province of ancestry. These factors will be tested for associations with cancers of the colon and rectum separately and with cancers of the large intestine as a whole. We will examine sex and geographic differences in relative risks for etiologic factors, location of tumors within the large bowel, histologic subtype of adenocarcinoma, and frequency of accompanying polyps.

[Estrogen receptor (ER) status of breast cancer cells. I. Classification of breast cancer cells bound with fluoresceinate-estrogen]

Based on the location and intensity of fluoresceinate-estradiol or 17-fluoresceinate-estrone bound to breast cancer cells, the estrogen receptor (ER) status of breast cancer cells were classified into A. B. C. D and E types. The type A was the entire cell marked with fluorescent brightness, B was nucleus marked with fluorescence but not the cytoplasm, C was cytoplasm but not the nucleus, D was only the nucleolus concentrated with fluorescence and type E was very faint fluorescence presented in the entire cell. Types A, B and C were taken as positive, and the others negative. Twenty human breast cancer cells bound with fluoresceinate-estradiol were evaluated by computer image processing technique and it was demonstrated that each of the five types of cells could be identified. The instant and contiguous observation after dropped the 17-fluoresceinate-estrone demonstrated the simultaneous presence of all these five types of cells. The breast cancer cells bound with fluorescence light the distribution of ER within a cell and, hence, the possibility of morphologic and biologic investigation of ER.

[Detection of estrogen receptor (ER) from needle aspirate in breast cancer cells]

With the increasing emphasis on earlier detection of breast cancer, detecting methods requiring only a small number of tumor cells are needed. This paper presents our experience of detecting the breast cancer ER with 17-fluoresceinated estrone (17-FE). The results were compared with that obtained from the same tumor by biochemical method. There is no direct quantitative relationship between the ER values (fmol/mg cytosol protein) determined by biochemical method and the proportion of ER containing cells observed by 17-FE method either in cells from needle aspirates prior to tumor removal or in cells from the removed tumor. It was found, however, that detecting the ER by 17-FE, all the tumors with ER levels greater than or equal to 10 fmol had greater than or equal to 10% marker positive cells, but 70% of tumors with negative or borderline (less than 10 fmol) ER levels had less than or equal to 10% ER positive cells. The correlation between the results from the biochemical method and those with 17-FE binding using needle aspirates was better than that between the former and the latter when using cells from fragments of removed tumor. The lack of concordance in 17-FE binding between the needle aspirates and parts of the removed tumor may be related to the diverse cellular composition of a tumor and the way of obtaining the sample. Our experience in this and previous studies show that further study and trial are worthwhile.

Relation of estrogen and its receptor to rat liver growth and regeneration

A variety of hormones have been implicated in the process of liver regeneration. Despite the demonstration of specific estrogen receptors (ER) in mammalian liver and the identification of responses to estrogen which occur in liver, there has been little or no investigation of the relation of that hormone or its receptor to liver regeneration or liver growth. This report provides information which indicates: (a) the effect of 17 beta-estradiol on the mass of both intact and regenerating rat liver; (b) the percentage of hepatocytes in neonatal and adult normal intact livers which contain ER, i.e., the estrogen receptor index (ERI); (c) changes in ERI and in nuclear ER occurring in that cell population following partial hepatectomy (PH) and/or 17 beta-estradiol administration; and (d) the temporal relation of the changes in ER with those related to DNA synthesis and liver regeneration and to liver growth. Approximately 55 to 60% of parenchymal cells from intact livers in adult rats were found to contain ER which was entirely located in the cytoplasm. No nuclear ER was evident in such cells. By 1 hr, and subsequently following 17 beta-estradiol administration to such animals, there resulted a depletion in the number of ER-containing cells and the identification of nuclear ER. These changes were followed by the onset of increased DNA synthesis and an increase in liver weight (p less than 0.001). Subsequent to 70% PH, a similar series of events occurred in liver remnants. Not only was there a decrease in the ERI from 60% at the time of PH to 40% 3 hr later and 30% after 72 hr, there was a decrease in cytosol ER as well. Accompanying the decrease was an increase in the number of cells with nuclear ER. By 24 hr post-PH, 29% of the cells with ER displayed that receptor in their nuclei. At that time, DNA synthesis was at its peak, and liver regeneration was taking place. When 17 beta-estradiol was administered at the time of PH, there was a more rapid onset of translocation of ER to the nuclei of parenchymal cells. At PH, when 17 beta-estradiol was given, no cells displayed nuclear ER. One hr later, 18% of cells with ER had nuclear ER, in contrast to the finding that only 3% of cells had nuclear ER 1 hr post-PH when 17 beta-estradiol was not administered. Regeneration was greater (59 versus 73%; p = 0.003) when animals received 17 beta-estradiol prior to PH.(ABSTRACT TRUNCATED AT 400 WORDS)

Fluoresceinated estrone binding by cells from human breast cancers obtained by needle aspiration

Despite widespread use there are disadvantages associated with biochemical methods for ER determination. Since there is increasing emphasis on earlier detection of primary breast cancers there is clearly a need for a method which requires only small numbers of tumor cells. A variety of other clinical situations exist in which the availability of a technic that could supply information regarding tumor ER from a small cell population would be helpful. This report presents our experience with 17-fluoresceinated estrone (17-FE) binding for detecting the proportion of estrone binding cells in samples obtained by fine-needle aspiration of tumors prior to their removal. The findings from the aspirated cells employing 17-FE were compared with results obtained from aliquots of the same tumors following their removal using both cytochemical (17-FE) and biochemical (3H-estradiol binding) methods for ER determination. When biochemically determined ER values (fmol/mg cytosol protein) were compared to the proportion of fluorescent cells observed either in cells from needle aspirates prior to tumor removal or in cells from the removed tumor there was no direct quantitative relationship. That lack of correlation is to be expected and does not indicate that one or the other method is inappropriate. It was found, however, that 100% of tumors having ER levels greater than or equal to 10 fmol had greater than or equal to 10% marker positive cells. Fifty-four percent of tumors with a negative or borderline (less than 10 fmol) ER level had less than 10% marker positive cells. The less satisfactory correlation in biochemically ER negative tumors may be related to false negative biochemical determinations. The better correlation between results from the biochemical method and those with 17-FE binding using needle aspirates than between the former and the latter when cells from fragments of removed tumor were used for cytochemical analysis, and the lack of concordance in 17-FE binding by the two cell suspensions (from needle aspirates and from parts of the removed tumor) may be related to the heterogeneity of the cellular composition of a tumor as regards ER content and consequently to the methods of sampling. The authors' experience in this and previous studies using 17-FE for determination of the proportion of putatively ER positive cells indicate that the method is worthy of further evaluation and consideration for experimental and clinical use.

Behavior during hippocampal microinfusions: anticholinesterase-induced locomotor activation

Awake, unrestrained rats received direct bilateral infusions of the cholinesterase inhibitor, echothiophate, into the dentate gyrus during a 40-min experimental session in a holeboard/activity chamber. Additional animals were similarly tested during intrahippocampal infusions of a novel cholinesterase inhibitor, NBD-AP-MPF. The computerized behavioral pattern monitor recorded the animals' locomotor activity, holepoking, and rearing in a manner that permitted the reconstruction and analysis of their sequential patterns of movement. Both echothiophate and NBD-AP-MPF infusions produced dose-dependent increases in locomotor activity that were accompanied by increased holepoking and rearing. The hyperactivity induced by anticholinesterase infusions was qualitatively similar to the atropine-sensitive effects of infusions of the cholinergic agonist, carbachol, as previously reported. Dye infusions revealed that spread of the infusate was restricted to the dentate gyrus of the anterodorsal hippocampal formation. The locomotor activation caused by the echothiophate infusions into the dentate gyrus were interpreted as indicative of a role for the cholinergic septo-hippocampal pathway in the release of motor responding.

Test of radioimmunoassay validity in the presence of an isotope effect

An isotope effect, manifested as delayed elution of the labeled moiety, was detected in CO-chromatography of testosterone with [1,2,6,7-3H]testosterone on Celite. The isotope effect was smaller for [1,2-3H]testosterone and even smaller, but still significant, for [7-3H]testosterone. Because of the isotope effect, the test of validity of a testosterone radioimmunoassay had to be modified. Instead of testing the constancy of values for specific activity in individual chromatographic fractions, the slopes of specific activities exhibited by mixtures of plasma testosterone (pooled specimens of plasma from men and from women) with [1,2-3H]testosterone were compared with that yielded by authentic testosterone mixed with the same tracer. Because the slopes were statistically indistinguishable, the assay of testosterone in these materials appears to be valid. We suggest that comparison of the slopes of specific activities be used as the basis of validity tests whenever such an isotope effect is present.

Test of radioimmunoassay validity in the presence of an isotope effect

An isotope effect, manifested as delayed elution of the labeled moiety, was detected in CO-chromatography of testosterone with [1,2,6,7-3H]testosterone on Celite. The isotope effect was smaller for [1,2-3H]testosterone and even smaller, but still significant, for [7-3H]testosterone. Because of the isotope effect, the test of validity of a testosterone radioimmunoassay had to be modified. Instead of testing the constancy of values for specific activity in individual chromatographic fractions, the slopes of specific activities exhibited by mixtures of plasma testosterone (pooled specimens of plasma from men and from women) with [1,2-3H]testosterone were compared with that yielded by authentic testosterone mixed with the same tracer. Because the slopes were statistically indistinguishable, the assay of testosterone in these materials appears to be valid. We suggest that comparison of the slopes of specific activities be used as the basis of validity tests whenever such an isotope effect is present.