Biomedical subjects

B Zhang

Publications and source records attributed to B Zhang.

At least 433 records · Page 24Linked to original sources

PubMed1997

Comparison of IA-2 with IA-2beta and with six other members of the protein tyrosine phosphatase family: recognition of antigenic determinants by IDDM sera.

To study the expression of protein tyrosine phosphatases (PTPs) in pancreatic islets, a cDNA library from islet cells was constructed and analysed. Twenty-one different PTPs were found to be expressed in islet cells, including three previously unknown PTPs. One of these, IA-2beta, was cloned, sequenced, and found to be related to IA-2, a major autoantigen in insulin-dependent diabetes mellitus (IDDM). The intracellular and extracellular domains of IA-2beta were 74 and 27% identical, respectively, to the intracellular and extracellular domains of IA-2. Approximately 70 and 45% of sera from patients with IDDM had autoantibodies that immunoprecipitated recombinant IA-2 and IA-2beta, respectively. By use of deletion mutants, we were able to show that the autoantibodies reacted with the intracellular, and not the extracellular, domains of IA-2 and IA-2beta, and that the major antigenic determinants resided within the COOH-terminus of the intracellular domains. Further studies revealed that approximately 97% of the IDDM sera that reacted with IA-2beta also reacted with IA-2, whereas only 50% of IDDM sera that reacted with IA-2 also reacted with IA-2beta. In contrast to the reactivity of IDDM sera with the IA-2 and IA-2beta, IDDM sera did not react with six other members of the PTP family. It is concluded that many members of the PTP family are expressed in pancreatic islets, but thus far only IA-2 and IA-2beta appear to be recognized as autoantigens by IDDM sera.

Amino Acid Sequence↗

PubMed1997

Prospective study of early detection for primary liver cancer.

PURPOSE: To determine whether repeated screening can lead to early detection of primary liver cancer (PLC) and in turn to an improved clinical result. METHODS: In this randomized controlled study, Shanghai urban residents aged 35-55 years and with serum evidence of HBV infection or chronic liver disease were eligible for recruitment. Using cluster sampling, these subjects were allocated into two groups-the screening group and the control group: there were 8109 subjects in the screening group and 9711 in the control group. Subjects in the screening group were tested with serum AFP and real-time ultrasound every 6 months. One to four rounds of screening were completed. Liver cancer was treated according to stage at diagnosis. RESULTS: All subjects enrolled were followed up and classed at the end-point as alive without liver cancer, alive with liver cancer, dead from liver cancer, or dead from another cause. The mean follow-up was 1.2 years; total follow-up was 12,038 person-years in the screening group and 9,573 person-years in the control group. We detected 38 patients with PLC in the screening group and 18 patients with PLC in the control group. In the patients in the screening group 76.8% of patients were at a subclinical stage, and 70.6% of them underwent resection, the 1- and 2-year survival rates being 88.1% and 77.5%, respectively. However, in the control group, none of the patients was at a subclinical stage when diagnosed, none of them underwent resection, and none of them survived over 1 year. The lead time was estimated at 0.45 years. The cost of detecting PLC at an early stage was RMB 12,600 (US$1,500). CONCLUSION: The study proved that screening the high-risk population for PLC with a serum AFP test and real-time ultrasound examination can detect patients in the early stages, increase the resection rate and prolong the survival time. It is therefore recommended that screening for PLC be advocated in any high-risk area.

Adult↗

PubMed1997

Relationship between fecal sampling times and sensitivity and specificity of immunochemical fecal occult blood tests for colorectal cancer: a comparative study.

PURPOSE: The present study was conducted to assess the accuracy of three testing methods using an immunochemical fecal occult blood test based on the number of samples as the optimum means for screening of colorectal cancer. METHOD: One hundred eighty-four patients with colorectal cancer and 368 healthy controls served as the subjects for this study. Each subject was tested by an immunochemical fecal occult blood test for three consecutive days. For evaluation of the most desirable number of sampling times, we used the results of the first day for the one-day method, results of the first and second days for the two-day method, and results of three consecutive days for the three-day method. Sensitivities and specificities of the three testing methods were evaluated. RESULTS: Sensitivities of an immunochemical fecal occult blood test were calculated as 67.9 percent for the one-day method, 88 percent for the two-day method, and 90.8 percent for the three-day method; specificity was as follows: 97.5 percent for the one-day method, 95.6 percent for the two-day method, and 92.1 percent for the three-day method. A significant difference in sensitivity was shown between the one-day and two-day and the one-day and three-day methods (P < 0.01); also, a significant difference in specificity was shown between one-day and three-day and two-day and three-day methods (P <0.05). CONCLUSIONS: These results indicate that the two-day method is recommended for immunochemical fecal occult blood testing as a means of screening for colorectal cancer.

Antibodies, Monoclonal↗

PubMed1997

Correction of the Bloom syndrome cellular phenotypes.

Bloom syndrome (BLM) is a genetic disorder associated with predisposition to cancer and chromosome instability. However, the most readily recognized clinical feature of the syndrome is growth retardation. Introduction of the previously cloned BLM gene into BLM cells yielded correction of the chromosome instability and slow growth phenotypes. Additionally, asynchronous cultures of complemented clones revealed a lower percentage of cells in S-phase than uncomplemented BLM cells. These results support the notion that BLM is a defect in which short stature, chromosome instability and cancer predisposition are all associated with an error in DNA replication.

Adenosine Triphosphatases↗

PubMed1997

Detection rate of immunochemical fecal occult blood test for colorectal adenomatous polyps with severe dysplasia.

This study was conducted to assess the accuracy of an immunochemical occult blood test for detecting colorectal adenomas with severe dysplasia, and to determine the relationship between the grading of adenomatous dysplasia and the results of this test. Sixteen colorectal adenomas under 1 cm with severe dysplasia, 65 adenomas under 1 cm with mild-to-moderate dysplasia, 65 adenomas 1 cm or larger with mild-to-moderate dysplasia, 65 colorectal cancers and 130 healthy controls were investigated. Each subject was tested with an immunochemical fecal occult blood test on 3 consecutive days, and the accuracy of the test was evaluated. The detection rate of this test was 13% for severe dysplasia under 1 cm, 45% for severe dysplasia 1 cm or more, 17% for mild-to-moderate dysplasia under 1 cm, 40% for mild-to-moderate dysplasia 1 cm or more, and 89% for colorectal cancers, and the false positive rate was 5%, showing a significant difference in the detection rate between severe dysplasias 1 cm or more and those under 1 cm (P < 0.05) as well as significant difference between severe dysplasias 1 cm or more and mild-to-moderate dysplasia under 1 cm (P < 0.01), and between cancers and adenomas (P < 0.001), whereas there was no significant difference between the detection rates for severe dysplasia 1 cm or more and mild-to-moderate dysplasia 1 cm or more. These results indicate that there is no association between the detection rate of this immunochemical occult blood test for adenomas and the grade of adenomatous dysplasia.

Adenoma↗

PubMed1997

Immunochemical fecal occult blood test is not suitable for diagnosis of hemorrhoids.

PURPOSE: This study was conducted to clarify the diagnostic value of an immunochemical fecal occult blood test for hemorrhoids. PATIENTS AND METHODS: In a case-control study, an immunochemical fecal occult blood test with a 2-day method was carried out on 82 subjects with hemorrhoids, on 82 subjects with colorectal cancer, and on 82 healthy subjects. In a population-based cross-sectional study, 29,714 subjects who received an immunochemical occult blood screening with a 2-day method were divided into two groups, according to the results of a questionnaire on hemorrhoids, and the positivity rate of an immunochemical test as well as the predictive value for colorectal cancer were compared in the two groups. Moreover, both an immunochemical occult blood test with a 2-day method and colonoscopy were conducted at the same time on asymptomatic subjects during a medical checkup. RESULTS: In the case-control study, the test was positive in 13.4% subjects with hemorrhoids, in 84.1% subjects with colorectal cancer, and in 4.9% healthy subjects, respectively, showing a significant difference in the detection rate between the two diseases (P < 0.001). In the population screening program, the test was positive in 6.9% subjects with hemorrhoids and in 6.5% subjects without hemorrhoids, and the predictive value was 3.2% in subjects with and without hemorrhoids, respectively, indicating no significant difference in the positivity rate as well as the predictive value between the two groups. Among 232 subjects in a medical checkup, 28 patients with hemorrhoids and 21 patients with colorectal polyp 1 cm or larger were diagnosed by colonoscopy, and the occult blood test was positive in 16.7% patients with hemorrhoids and in 52.4% patients with colorectal polyp, respectively. There was a significant difference in the sensitivity between the two disease groups (P < 0.05). CONCLUSIONS: These findings indicate that the immunochemical fecal occult blood is unsuitable for the diagnosis of the patients with hemorrhoids and an examination of the colorectum is necessary in cases where the occult blood test is positive but there is a sign of hemorrhoids.

Aged↗

PubMed1997

One-shot delayed-type hypersensitivity reaction in the mouse liver causes a sustained liver injury to picryl chloride.

The developmental characteristics of liver injury induced by a delayed-type hypersensitivity (DTH) mechanism against picryl chloride were examined for 9 consecutive weeks in 3 mouse strains, BALB/c, Kunming and ICR mice. The changes of most biochemical parameters were similar in these three strains, namely, the activities of serum transaminases, lactic dehydrogenase, and prolidase were elevated significantly on day 1, during the first several weeks, and almost throughout the duration, respectively, of liver injury. The content of liver hydroxyproline was also increased after 1-9 weeks of liver injury. In addition, a significant decrease of liver weight, serum alkaline phosphatase and albumin level was observed in BALB/c and Kunming mice. Similar changes in liver histology were also found in the three strains. The hepatocellular necrosis and inflammatory infiltration into the portal area were the predominant features on day 1 and were still distinct during the subsequent several weeks. The mild or moderate hepatocellular degeneration, regeneration and connective tissue hyperplasia were observed after 1 or 3 weeks. A bridging necrosis between portal and portal was observed in several BALB/c and ICR mice, reflecting the possibility of exacerbation of liver injury. These results suggest that the liver injury could be caused and sustained by a one-shot DTH reaction to picryl chloride. The chronicity of the biochemical and histopathological characteristics may be helpful in elucidating the mechanisms of chronic development of liver injury.

Animals↗

PubMed1997

Quantification of the effects of troglitazone on insulin sensitivity and beta-cell function in Watanabe heritable hyperlipidemic rabbits: a minimal model analysis.

Troglitazone is a newly developed antidiabetic drug that has been shown to improve insulin resistance and hyperinsulinemia both in diabetic animal models and in patients with non-insulin-dependent diabetes mellitus. The Watanabe heritable hyperlipidemic (WHHL) rabbit, an animal model of familial hypercholesterolemia, is characterized by hyperinsulinemia, which reflects insulin resistance. In this study to determine the effects of troglitazone on glucose and insulin metabolism in WHHL rabbits, we quantified the rate of glucose utilization (glucose tolerance index [Kg]), sensitivity of first-phase posthepatic insulin secretion to glucose (phi1), sensitivity of second-phase posthepatic insulin secretion to glucose (phi2), insulin sensitivity to glucose disposal ([Si] inversely related to insulin resistance), insulin-independent glucose disposal (glucose effectiveness [Sg]), and rate of insulin clearance (Ki) by incorporating our previously reported two-compartment model of a glucose/insulin system with the glucose disappearance model of Bergman. Galvin insulin sensitivity (GIS) was also computed for comparison with Bergman Si. When troglitazone was administered as a food admixture (24 mg/d per animal) for 6 months, it did not significantly affect beta-cell function as measured by phi2, glucose tolerance as measured by Kg, or Sg, but increased both Si and Ki and reduced phi1, leading to a decreased plasma insulin response during the intravenous glucose tolerance test (IVGTT). Si was strongly and significantly correlated with GIS. These data indicate that in WHHL rabbits, troglitazone improves insulin sensitivity and posthepatic insulin clearance without affecting beta-cell function or glucose tolerance.

Animals↗

PubMed1997

Scanning tunnelling microscopy observation of cytochrome-c denaturation induced by bromopyrogal red on highly oriented pyrolytic graphite.

The denaturation of cytochrome-c (cyt-c) induced by bromopyrogal red (BPR) was studied by scanning tunnelling microscopy (STM) on the electrochemically pretreated highly oriented pyrolytic graphite (HOPG) surface. STM images reveal that denatured cyt-c molecules exist in variable states including aggregates, globular compact, partially unfolded and combined with BPR molecule. The apparently low image contrast of denatured cyt-c observed in this experiment comparing to that of native cyt-c molecules, and the relative low image contrast of the unfolded part comparing with the compact globular part, are ascribed to the unfavourable tunnelling paths for the conformational variations of denatured cyt-c molecules.

Animals↗

PubMed1997

Are free radicals responsible for endothelial cell killing of Staphylococcus aureus?

We have recently demonstrated that endothelial cells cultured on Gelfoam blocks, but not monolayer matrices can phagocytose and kill Staphylococcus aureus. Experiments determined that penicillin G, included in the endothelial cell growth medium, induces these cells to exhibit the observed bactericidal activity. In this communication, we report on studies aimed at elucidating the mechanism by which penicillin G-induced endothelial cells, cultured on Gelfoam blocks, kill S. aureus. Despite the fact that there is a substantial literature that demonstrates neutrophilic killing of bacteria can be mediated through free radical-dependent and free radical-independent mechanisms, considerably less is known about pathways by which endothelial cells can catalyze similar microbicidal activities. Studies described herein point to the fact that superoxide and products derived from this free radical were not responsible for endothelial killing of S. aureus. Likewise, a possible role for nitric oxide in bacterial killing was explored. As part of this inquiry, we stably transduced a NOS-2 encoding retrovirus into endothelial cells cultured on Gelfoam blocks in the absence of penicillin G. Even though these cells secreted nitric oxide at a rate of 0.5 microM/h per 1 x 10(6) cells, similar to what has been reported for murine macrophages induced with gamma-interferon, in our model, nitric oxide was not found to kill S. aureus. Data presented demonstrate that the microbicidal activity of endothelial cells is mediated through free radical-independent pathways.

Animals↗

PubMed1997

Endothelin-1 induces liver vasoconstriction through both ETA and ETB receptors.

BACKGROUND/AIMS: We investigated which endothelin receptors mediate the vasoconstrictive effects of endothelin-1 on liver circulation. METHODS: An isolated perfused rat liver model in recirculation was used. RESULTS: The perfusion of 10(-10) M endothelin-1 had no significant influence on the liver flow, whereas 10(-9) M endothelin-1 induced significant vasoconstriction, with flow dropping from 3.20 +/- 0.34 to 1.48 +/- 0.28 ml. min-1.g-1 liver tissue (p < 0.01 vs controls). The liver flow was interrupted following the perfusion of 10(-8) M endothelin-1. Sarafatoxin C and BQ 3020, two agonists of ETB receptor, had vasoconstrictive effects in this model. Sarafatoxin C decreased the liver flow in a dose-dependent manner, from 3.32 +/- 0.21 to 2.18 +/- 0.20, 1.60 +/- 0.09, and 1.01 +/- 0.06 ml.min-1. g-1, respectively, with 10(-9) M, 10(-8) M, and 10(-7) M. While BQ 123, an antagonist of ETA receptor, or BQ 788, an antagonist of ETB receptor, partially reversed the effect of 10(-9) M endothelin-1, the simultaneous administration of BQ 123 and BQ 788 completely reversed these effects. CONCLUSIONS: These results indicate that the vasoconstrictive effects of endothelin-1 on the liver circulation are mediated through both ETA and ETB receptors.

Animals↗

PubMed1997

NO-mediated vasodilation in the rat liver. Role of hepatocytes and liver endothelial cells.

BACKGROUND/AIMS: Nitric oxide (NO) is a potent vasodilator. We investigated the mechanisms responsible for this effect in the liver. METHODS: Isolated perfused rat liver and cultures of endothelial sinusoidal cells and hepatocytes were used. RESULTS: L-arginine (10(-3) M) and NO donor Sin-1 (10(-5) M) respectively increased the liver flow by 52% (p<0.01) and 93% (p<0.01) vs controls. The NO synthase inhibitor Nw-nitro-L-arginine (10(-3) M) and the guanylate cyclase inhibitor methylene blue (10(-5) M) respectively decreased the basal liver flow by 26% and 16% (p<0.05) and inhibited the vasodilating effects of L-arginine. L-arginine (10(-3) M) increased nitrite concentration in hepatocyte culture (77.25+/-7.40 micromol x l(-1) vs 14.70+/-3.55 micromol x l(-1) in controls; p<0.01) and in liver endothelial cell culture (0.36+/-0.09 micromol x l(-1) vs 0.12+/-0.05 micromol x l(-1) in controls; p<0.05). Nw-nitro-L-arginine inhibited the basal production and abolished the L-arginine-induced production of nitrites both in hepatocyte and in liver endothelial cell cultures. The concentration of nitrites in the hepatocyte supernatant rose from 14.70+/-3.55 micromol x l(-1) to 150.50+/-45.55 micromol x l(-1) in the presence of a combination of interleukin-1beta, TNF alpha and interferon gamma. CONCLUSIONS: Under basal conditions, NO regulates the vascular tone of liver circulation. Both liver endothelial cells and hepatocytes can be implicated. NO production by hepatocytes may increase during inflammation.

Animals↗

PubMed1997

Troglitazone lowers blood pressure and enhances insulin sensitivity in Watanabe heritable hyperlipidemic rabbits.

Although an association has been demonstrated between insulin resistance and hypertension, the mechanism of this association is not clear. Clarification of this point is important in hyperinsulinemic Watanabe heritable hyperlipidemic (WHHL) rabbits, an animal model of familial hypercholesterolemia, as hypertension markedly stimulates atherosclerosis in WHHL rabbits. The purpose of the present study was to determine whether troglitazone, a new thiazolidinedione drug for insulin resistance, could reduce blood pressure (BP) by improving hyperinsulinemia in WHHL rabbits. The effects of troglitazone, administered as a food admixture (24 mg/day) for 6 months, on hyperinsulinemia and BP were examined in WHHL rabbits. Insulin sensitivity (IS) was measured by the minimal model method using an intravenous glucose tolerance test (IVGTT). Troglitazone significantly reduced fasting insulin levels and the area-under-the-curve of insulin IVGTT profiles, indicating improved hyperinsulinemia. Troglitazone also significantly increased IS and reduced BP and heart rate (HR). Due to a significant correlation between HR and BP, a covariance analysis was performed. When BP was considered as a covariance factor, the change in HR was significant in treated rabbits. However, when HR was considered as a covariance factor, the change in BP was not significant, suggesting that reduced BP may be partly associated with changes in the sympathetic nervous system activity. In conclusion, troglitazone increases insulin sensitivity and lowers blood pressure in WHHL rabbits. Due to its dual effects on insulin resistance and hypertension, troglitazone offers a new pharmacological approach for the treatment of insulin-resistance syndrome.

Animals↗

PubMed1997

Risk of tongue cancer associated with tobacco smoking and alcohol consumption: a case-control study.

Recent studies indicate that cancer of the tongue is increasing rapidly among the younger population in many parts of the world. Few studies, however, have directly examined the risk factors for the disease. A case-control study was conducted in Beijing, China to investigate risk factors for tongue cancer. A total of 111 cases and 111 controls aged 20-80 years were included in this study. The results show that risk of tongue cancer is significantly elevated among ex-smokers (OR = 2.24, 95% CI = 1.09-4.62) and among current smokers (OR = 2.73, 95% CI = 1.26-5.91). The risk increases with increasing tobacco consumption, as reflected by both cigarette equivalents smoked per day and lifetime pack-years of tobacco smoking. Quitting smoking was associated with a reduction of the risk of tongue cancer. The numbers of cases in the study, however, is small, preventing further analyses during the years after quitting smoking. Overall, alcohol drinking was not found to be significantly associated with the risk of tongue cancer in this study (OR = 1.20, 95% CI = 0.58-2.50 for current drinkers). However, a marginally significant association was found for those who drank spirits at least 5 days a week (OR = 2.34, 95% CI = 0.90-6.06). A suggestion of effect modification for smoking and alcohol drinking was observed in this study.

Adult↗

PubMed1997

Similarities and differences between nonhomologous proteins with similar folds: evaluation of threading strategies.

BACKGROUND: There are many pairs and groups of proteins with similar folds and interaction patterns, but whose sequence similarity is below the threshold of easily recognizable sequence homology. The existence of multiple sequence solutions for a given fold has inspired fold prediction methods in which structural information from one protein is used to estimate the energy of another, putatively similar, structure. RESULTS: A set of 68 pairs of proteins with similar folds and sequence identity in the 8-30% range is identified from the literature. for each pair, the energy of one protein, calculated using knowledge-based statistical potentials, is compared to the estimated energy, calculated with the same potentials but using the structural information (burial status and interaction pattern) of another protein with the same fold. Different energy estimates, corresponding to approximations used in various fold recognition algorithms, are calculated and compared to each other, as well as to the correct energy. It is shown that the local energy terms, based on burial and secondary structure preferences, can be reliably estimated with an accuracy close to 70%. At the same time, the two-body nonlocal energy loses over 60% of its value due to the repacking of the structure. Further approximations, such as the 'frozen approximation', can bring it to an essentially random value. CONCLUSIONS: Local energy terms could be used safely to improve fold recognition algorithms. To utilize pair interaction information, specially designed pair potentials and/or a self-consistent description of pair interactions is necessary.

Algorithms↗

PubMed1997

Mechanism of action of gemfibrozil on HDL metabolism and atherosclerosis in WHHL rabbits.

We investigated the mechanism of action of gemfibrozil on high-density lipoproteins (HDL) and apolipoprotein (apo) A-I metabolism and atherogenesis in homozygous Watanabe heritable hyperlipidemic (WHHL) rabbits, an animal model of familial hypercholesterolemia and HDL deficiency. Two-month-old WHHL rabbits were fed either a normal control diet or a diet containing 0.5% gemfibrozil for 12 months. In vivo apo A-I kinetics, the fractional rate of cholesterol esterification in HDL (FER[HDL]), which reflects the reactivity of HDL to lecithin:cholesterol acyltransferase, and a morphometrical analysis of atherosclerotic lesions in the descending thoracic aorta, were examined. At 12 months, the mean levels of serum total cholesterol, LDL cholesterol (LDL-C), and HDL cholesterol (HDL-C) in both groups had decreased to approximately 53%, 57%, and 87% of the initial levels (at 0 month), respectively, which is characteristic of homozygous WHHL rabbits of the physiologic influence of aging, and no differences in the levels of serum LDL-C, HDL-C, and triglycerides were found between the two groups. Rabbits treated with gemfibrozil exhibited a decreased FER(HDL) (38% of the controls, P = 0.039). Gemfibrozil induced a significant increase in the total mass of apo A-I (1.7-fold, P < 0.05) and in the rate of apo A-I synthesis (1.6-fold, P < 0.05). The atherosclerotic intimal area was positively correlated with serum LDL-C (P = 0.02) in both groups, but gemfibrozil did not affect the atherosclerotic intimal area. These results indicate that 12 months of treatment with gemfibrozil did not protect against atherosclerosis despite a significant increase in apo A-I synthesis and enhanced HDL function through FER(HDL). It is possible that both the qualitative and quantitative improvement in HDL by gemfibrozil cannot overcome the massive and long-term exposure of the vascular wall to LDL in these animals.

Animals↗

PubMed1997

Binding of vanadate to human erythrocyte ghosts and subsequent events.

Spectroscopic techniques were used to investigate the interaction between vanadate and human erythrocyte ghosts. Direct evidence from 51 V nuclear magnetic resonance (NMR) studies suggested that the monomeric and polymeric vanadate species may bind to the anion binding sites of band 3 protein of the erythrocyte membrane. The results of 51V NMR studies and the quenching effect of vanadate on the intrinsic fluorescence of the membrane proteins indicated that in the low concentration range of vanadate (< 0.6 mM), monomeric vanadate binds mostly to the anion sites of band 3 protein with the dissociation constant close to 0.23 mM. The experiments of sulfhydryl content titration by the method of Ellman and residue sulfhydryl-labeled fluorescence spectroscopies clearly displayed that vanadate reacts directly with sulfhydryl groups. The appearance of the anisotropic election spin resonance (ESR) signal of vanadyl suggests that a small (c.3%) amount of vanadate was reduced by sulfhydryl groups of membrane proteins. The fluidity and order of intact ghost membrane were reduced by the reaction with vanadate, as shown by the ESR studies employing the protein- and lipid-specific spin labels. It was concluded that although vanadates mainly bind to band 3 protein, a minor part of vanadate may oxidize the residue sulfhydryl groups of membrane proteins, and thus decrease the fluidity of erythrocyte membrane.

Anion Exchange Protein 1, Erythrocyte↗

PubMed1997

Association of DNA with nuclear matrix in in vitro assembled nuclei induced by rDNA from Tetrahymena shanghaiensis in Xenopus egg extracts.

The nuclei assembled from exogenous DNA or chromatin in egg extracts resemble their in vivo counterparts in many aspects. However, the distribution pattern of DNA in these nuclei remains unknown. We introduced rDNA from the macronuclei of Tetrahymena into Xenopus cell-free extracts to examine the association of specific DNA sequences with nuclear matrix (NM) in the nuclei assembled in vitro. Our previous works showed the 5'NTS (non-transcription sequences) of the rDNA specifically bind to the NM system in the macronuclei. We show now the rDNA could induce chromatin assembly and nuclear formation in Xenopus cell-free system. When we extracted the NM system and compared the binding affinity of different regions of rDNA with the NM system, we found that the 5'NTS still hold their binding affinity with insoluble structure of the assembled nuclei in the extracts of Xenopus eggs.

Animals↗