A processive versus a distributive mechanism of action correlates with differences in ability of normal and xeroderma pigmentosum group A endonucleases to incise damaged nucleosomal DNA

A DNA endonuclease, isolated from the nuclei of normal human and xeroderma pigmentosum complementation group A (XPA) cells, which recognizes predominately pyrimidine dimers, was examined for the mechanism by which it locates sites of damage on UVC-irradiated DNA. In reaction mixtures with low ionic strengths (i.e. lacking KCl), the normal and XPA endonuclease locate sites of UV damage on both naked and reconstituted nucleosomal DNA by different mechanisms. On both of these substrates, the normal endonuclease acts by a processive mechanism, meaning that it binds non-specifically to DNA and scans the DNA for sites of damage, whereas the XPA endonuclease acts by a distributive one, meaning that it randomly locates sites of damage on DNA. However, while both the normal and XPA endonucleases can incise UVC irradiated naked DNA, they differ in ability to incise damaged nucleosomal DNA. The normal endonuclease showed increased activity on UVC treated nucleosomal DNA compared with naked DNA, whereas the XPA endonuclease showed decreased activity on the damaged nucleosomal substrate. Since a processive mechanism of action is sensitive to the ionic strength of the micro-environment, the KCl concentration of the reaction was increased. At 70 mM KCI, the normal endonuclease switched to a distributive mechanism of action and its ability to incise damaged nucleosomal DNA also decreased. These studies show that there is a correlation between the ability of these endonucleases to act by a processive mechanism and their ability to incise damaged nucleosomal DNA; the normal endonuclease, which acts processively, can incise damaged nucleosomal DNA, whereas the XPA endonuclease, which acts distributively, is defective in ability to incise this substrate.      

A new amino acid mixture permits new approaches to the treatment of phenylketonuria

A new amino acid mixture for incorporation into medical foods for the treatment of hyperphenylalaninemia has been tested in a regular clinic. The mix is designed to be as unobtrusive as possible, consistent with good nutrition. After more than 1 year of trial as a beverage, we have shown that it is safe and well tolerated but that plasma phenylalanine is no better controlled than with some other products. The mix can be incorporated into a large number of different foods without affecting the taste. Occult monitoring of the quantity of medical foods purchased compared with the amounts reported to be consumed in diet histories provides an excellent way to monitor dietary compliance.     

Characterization of urothelial carcinoma with respect to the content of carcinoembryonic antigen in exfoliated cells.

A sutstance immunologically similar to carcinoembryonic antigen (CEA) was demonstrated in urothelial bladder carcinoma cells. When indirect immunofluorescence with specific anti-CEA antisera was used, CEA-containing cells were seen in 18 out of 40 cases in 5% to 30% of the cells. Among patients with tumor cells of well differentiated morphology, 61% had CEA-containing cells, compared with only 24% of patients with a poorly differentiated tumor. Microfluorometry of single cells was performed in six cases to estimate the range of CEA content. The mean fluorescence intensity with anti-CEA antiserum was three to six times that of the same tumor cell population stained with non-immune rabbit sera. This fluorescence was decreased when the anti-CEA anti-sera were incubated with CEA but not with nonspecific cross-reactive antigen. The results show a wide range of CEA antigen content in exofoliated bladder tumor cells. In addition to proliferative status and differentiation, quantitative CEA measurements give further possibilities to study characteristics of tumor cell populations.     

Multiple antigens as marker substances in germinal tumors of the testis.

Germinal cell tumors of the testis were studied for the presence of several tumor-associated antigens. Antisera were produced by immunizing rabbits with the purified antigens of alpha-fetoprotein (AFP), carcinoembryonic antigen (CEA), and hepatoma ferritin. Indirect immunofluorescence on embryonal carcinoma with or without teratoma components demonstrated that their staining range was 1--60 per cent with antiserum against AFP, 0--16 per cent with anti-serum against ferritin, and 0-40% with antiserum against CEA. Ferritin-like substances have not been described previously in germinal tumors of the testis. No staining was seen with seminoma cells or benign testicular tissues. Raised serum levels of AFP and the ferritin-like substance were related both to the presence of tumor and to dissemination of the disease. CEA occurred transiently in serum. Eleven patients with primary tumors had no antigen in their sera and have all survived, but the median survival time for 8 patients with either antigen in preoperative sera was 12 months. Five patients with advanced tumor in whom neither AFP nor ferritin was detected had a much longer median survival time (58 mo) than did 13 patients with high levels of serum AFP or ferritin (12 mo). The presence of either AFP or ferritin in sera of patients with primary or advanced disease, therefore, seemed to indicate a poor prognosis. The determination of both substances in serum may be useful in the follow-up of patients with certain types of testicular tumors. The proportion of cells containing each antigen varied in the different tumors. Similarly, each antigen could occur independently in serum. This suggested that certain germ cell tumors contained subpopulations of cells, which differed in their production and release of the antigens studied.     

DNA pattern and cytological findings in fine-needle aspirates of untreated prostatic tumors. A flow-cytofluorometric study

The cellular DNA content in fine-needle prostatic aspirates from 500 untreated patients was determined by flow cytofluorometry. According to the DNA patterns diploid, tetraploid, and non-tetraploid aneuploid cases were identified. In 301 cytologically benign cases more than 90% showed diploid DNA patterns. Among 166 carcinomas the incidence of aneuploid DNA values increased with the degree of anaplasia, ie, 44% in well-differentiated, 78% in moderately differentiated, and 97% in poorly differentiated tumors. In aneuploid cases of well-differentiated carcinomas almost exclusively tetraploid DNA patterns were observed, while in poorly differentiated carcinomas about 80% showed non-tetraploid aneuploid DNA distributions. Among aneuploid cases of moderately differentiated carcinomas 2/3 were tetraploid and 1/3 non-tetraploid aneuploid. Morphologically similar tumors may thus be separated by the DNA profiles. The biological significance of these results must be further evaluated by clinical follow-up of the patients.     

Death receptor signals to mitochondria

Apoptosis is the best-characterized form of programmed cell death (PCD) and is of fundamental importance in tissue homeostasis. In mammalian systems, there are two major pathways that are involved in the initiation of apoptosis: the "extrinsic" death receptor pathway and the "intrinsic" mitochondrial pathway. Although these pathways act independently to initiate the death machinery in some cellular systems, in many cell types, including numerous tumor cells, there is delicate coordination and cross talk between the extrinsic and intrinsic pathways, which leads to the activation of the executioner caspase cascade. Additionally, there appears to be a fine balance between the caspase-mediated arm of death receptor signaling that engages mitochondria and the caspase-independent arm that promotes vacuole proliferation in many cells. Here, we review our current knowledge about the layers of complexity that are posed by the interactions between death receptor-induced pathways and how they influence mitochondria to regulate cellular life and death decisions.     

Relationship of systemic hemodynamics, left ventricular structure and function, and plasma natriuretic peptide concentrations during pregnancy complicated by preeclampsia

OBJECTIVE: This study was done to evaluate left ventricular structure and function among pregnant patients with preeclampsia and compare them with those of normotensive pregnant and nonpregnant subjects. It also tested the hypothesis that abnormalities in left ventricular structure and function are associated with elevated plasma levels of natriuretic peptides. STUDY DESIGN: The study compared 75 pregnant women (n = 40 with preeclampsia; n = 35 normotensive pregnant women) and 10 nonpregnant normotensive control subjects undergoing an echocardiographic and biohumoral (renin activity and aldosterone, atrial natriuretic peptide, and brain natriuretic peptide concentrations) evaluation. The statistical analysis was carried out by analysis of variance, and significance was set at P <.05. RESULTS: Comparison of pregnant patients with preeclampsia versus both normotensive pregnant women and nonpregnant women showed significant increases in left ventricular mass and left ventricular endsystolic and end-diastolic volumes and significant reductions in left ventricular ejection fraction and percentage of fractional shortening. These changes coincided with increases in plasma levels of atrial natriuretic peptide and brain natriuretic peptide that were linearly related to the left ventricular structural and functional changes observed in patients with preeclampsia. CONCLUSION: Pregnant patients with preeclampsia showed adaptation to the increase in systemic blood pressure, with significant modification of left ventricular structure and function related to the plasma levels of both atrial natriuretic peptide and brain natriuretic peptide. A simple evaluation of plasma natriuretic peptide concentrations could help to discriminate patients with preeclampsia who have a condition of mild left ventricular overload.     

B7-1和IL-12基因转染对肝癌细胞免疫原性的影响

目的 观察Ｂ７－１和ＩＬ－１２基因表达对人肝癌细胞免疫原性原影响。方法 分别将Ｂ７－１和ＩＬ－１２基因以逆转录病毒介导转染ＨｅｐＧ２细胞。阳性克隆细胞与健康人外周血淋巴细胞（ＰＢＬ）混合培养后,用流式细胞仪检测ＰＢＬ表面Ⅰ类人白细胞抗原（ＨＬＡ－Ⅰ）分子表达,以ＭＴＴ法检测ＰＢＬ的特异性杀伤活性Ｋ５６２细胞的活性。结果 混合ＨｅｐＧ２／Ｂ７－１ＨｅｐＧ２／ＩＬ－１２细胞组ＰＢＬ表面的ＨＬＡ－Ⅰ分子