PubMed Health⌕ Search

Biomedical subjects

T Cheng

Publications and source records attributed to T Cheng.

79 records · Page 5Linked to original sources
PubMed1978

Characterization of 5'-terminal methylation of human alpha- and beta-globin mRNAs.

After incubating peripheral blood of various anemic individuals with [methyl-3H]methionine, 5'-terminal cap structures and the sequential methylation of human globin mRNAs were determined. Human alpha- and beta-globin mRNAs have the same methylated nucleotides at their 5' ends as the alpha- and beta-globin mRNAs of mouse and rabbit: m7G(5')ppp(5')[m6Am/Am]pCmp. The order of methyl group addition to human globin mRNA is also similar to that of mouse globin mRNA in that methylation of the 5'-terminal guanosine and the ribose of adenosine occurs earlier than that of the base of adenosine and the ribose of cytidine. Thus, both the cap structures and the order of methylation are conserved in the globin mRNAs of these species, suggesting that variation in the structure of the 5' terminus of globin mRNAs may alter the function of these molecules.

Anemia↗
PubMed1978

Sequential methylation of globin mRNA in nucleated erythroid cells and reticulocytes of mice.

The order of methylation of the 5'-terminus of globin mRNA of mice was studied by incubation of staged nucleated erythroid cells and peripheral reticulocytes with [methyl-3H] methionine. Methylation of the 5'-termini of alpha and beta- globin mRNAs in enucleated reticulocytes was demonstrated as follows: (a) [methyl-3H] incorporation into poly(A)+ RNA of reticulocytes co-migrated with the alpha- and beta- globin mRNAs on gel electrophoresis, and (b) following digestion of this RNA, radioactivity was localized to the four methyl sites at the 5'-capped structure of mouse globin mRNAs. However, this methylation is only 5 to 8% as efficient as in nucleated erythroid precursor cells, suggesting that most globin mRNA molecules are fully methylated prior to the reticulocyte stage. Incubations of early and late nucleated erythroid precursor cells and pulse-chase experiments with reticulocytes demonstrate that addition of the four 5'-terminal methyl groups follows an orderly sequence. In addition, the pulse-chase experiments suggest the turnover of the N7-methyl group on the 5'-terminal guanosine, but not of the other methyl groups in the 5'-terminus of globin mRNA. Thus, 5'-terminal methylation of globin mRNA is a nonrandom, dynamic process.

Animals↗
PubMedDate not supplied

Attributions of cause and recurrence in long-term breast cancer survivors.

UNLABELLED: Women are bombarded with information about the purported causes and the prevention of breast cancer. This survey sought to determine to what women survivors of breast cancer attributed the cause and lack of recurrence of their breast cancer, and whether these views were associated with specific health behaviors. METHODS: Women who had survived breast cancer without recurrence for at least 2 years were surveyed by mail about their views on the cause and lack of recurrence of their breast cancer. They were also asked to estimate their personal risk of cancer recurrence, report on their health behaviors, describe what advice they would give to women newly diagnosed with breast cancer, and what they would change if they had to relive their breast cancer experience. RESULTS: 378 (75.6%) women breast cancer survivors responded who had been recurrence free for a mean of 8.6+/-11.8 years. Women (n=322) who responded to the question about the cause of breast cancer attributed it to stress (42.2%), genetics (26.7%), environment (25.5%), hormones (23.9%), don't know (16.5%), diet (15.5%), and breast trauma (2.8%). Women (n=330) who responded to the question about what prevented cancer recurrence attributed it to positive attitude (60.0%), diet (50.0%), healthy lifestyle (40.3%), exercise (39.4%), stress reduction (27.9%), prayer (26.4%), complementary therapies (11.2%), don't know (5.1 %), luck (3.9%), and tamoxifen (3.9%). Most women felt their recurrence risk was average (44.8%), or below average (35.8%). Some attributions of breast cancer cause or lack of recurrence were associated with specific health behaviors. The majority of women survivors would advise other women with breast cancer to be positive, and if they had to relive their cancer experience they would take more control of their treatment. DISCUSSION: Despite lack of evidence substantiating stress as a cause of breast cancer, many breast cancer survivors believed stress caused their cancer. An even higher percentage of survivors believed their positive attitude had prevented breast cancer recurrence and they would advise other women with breast cancer accordingly. Attribution beliefs clearly affected survivors' health behaviors. CONCLUSION: Healthcare providers should consider the personal beliefs of patients about cancer cause and recurrence, which may be at variance with scientific evidence. This may assist in framing the management of patients in personally meaningful ways, which may increase health behaviors, adherence, satisfaction and quality of life. Whether it will increase survival remains unknown.

Adaptation, Psychological↗
PubMedDate not supplied

Long-term breast cancer survivors: confidentiality, disclosure, effects on work and insurance.

UNLABELLED: As more women are diagnosed with breast cancer, more will survive the illness from a few years to a lifetime. This study sought to determine the experience of Canadian breast cancer survivors with respect to the impact of cancer on confidentiality, work and insurance. METHOD: Women who had survived breast cancer without recurrence for at least 2 years completed a mail survey about the effect of their illness on confidentiality, disclosure, work and insurance. RESULTS: 378 (75.6%) women breast cancer survivors responded to the survey. Their mean age was 61.0+/-10.9 years, and 67.6% had been recurrence free for more than 5 years. The majority of women rated hospital staff, family doctors, family, friends, and support groups at the highest possible level of confidentiality. Over 70% of survivors disclosed their diagnosis to friends, children, siblings, and partners, while over 50% disclosed to work colleagues and supervisors. However, over 40% felt cancer had altered their priorities or progress at work, and 5% were afraid to change jobs in case they became ill again. There was a lack of knowledge about insurance but, of the types of insurance identified, life insurance (17.9%), extended health insurance (7.7%), and private disability insurance (4.4%) were reported to have been refused or offered only with higher premiums as a result of a past diagnosis of breast cancer. DISCUSSION: A substantial minority of women perceived that cancer had substantially affected their personal and work lives. Although most felt their illness confidentiality was well protected and they disclosed freely to family, friends, and work, over 40% of women survivors reported that cancer had affected their work in various ways, and nearly 20% identified insurance problems. It appears that disclosure sometimes results in negative work and insurance experiences. CONCLUSIONS: Health professionals and cancer survivors should engage in education about the potential positive and negative effects of disclosure, and advocacy against cancer-based work and insurance discrimination.

Adaptation, Psychological↗
PubMedDate not supplied

Prehospital identification of acute coronary ischemia using a troponin T rapid assay.

OBJECTIVE: To evaluate the performance of a rapid assay for cardiac troponin T (cTn-T) in patients with chest pain in the prehospital setting. METHODS: A prospective, observational clinical trial in a rural county served by a single emergency medical services system and two emergency departments. Patients fulfilling prehospital criteria to identify acute coronary ischemia (ACI) had a blood sample applied to the cTn-T rapid-assay device. Quantitative analysis of cTn-T was also performed on each sample at a later time. Medical records were reviewed to determine ultimate diagnoses. Non-admitted patients were followed by telephone at one week. Main outcome measures included the sensitivity, specificity, positive predictive value, and negative predictive value of the rapid cTn-T assay for detecting ACI defined as acute myocardial infarction (AMI) or unstable angina (UA) within one week of presentation. RESULTS: Of 87 patients enrolled, 29 were identified with ACI. This included 15 patients diagnosed as having AMI and 14 patients diagnosed as having UA. The cTn-T rapid-assay device was positive for five of 87 patients (5.7%); three were associated with AMI and two with UA. Measurement of a single cTn-T to detect ACI had a sensitivity of 17.2% (0.058, 0.358), specificity of 100% (0.950, 1), positive predictive value of 100% (0.549, 1), and negative predictive value of 70.7% (0.609, 0.806). CONCLUSION: The cTn-T rapid-assay device may be useful in the prehospital setting to identify a small number of patients with ACI. The authors caution, however, that a negative test in the prehospital setting cannot be used to rule out significant disease.

Acute Disease↗
PubMedDate not supplied

Post-transcriptional modification of globin RNA.

During the last three years, significant progress has been made in the characterization of the structure of globin RNA precursors and the steps involved in their modifications to mature mRNA. Aside from the coding sequence, IVSs in RNA precursors have a critical function in the formation of mature mRNA. However, certain questions regarding the role IVSs might have in RNA processing still need to be answered. In order to understand normal globin gene expression, it will be important to know whether specific nucleoside sequences or conformational changes in the structure of the RNA due to IVSs are required for each processing enzyme in the stepwise cleavage-ligation reaction. The availability of purified RNA processing intermediates for sequencing should enable us to map the cleavage-ligation sites in each RNA. It will be interesting to determine whether any methylated nucleotides exist in IVSs and whether methylation is involved in the processing pathway. In addition, further evidence should be forthcoming to demonstrate the importance of IVS removal in the transport of RNA from nucleus to cytoplasm. Information obtained from these studies should help us to understand further the post-transcriptional control of the globin gene expression in normal states as well as in states of abnormal globin chain synthesis, such as the thalassemias.

Amino Acid Sequence↗