viii (^) Leon V. Berhardt
structure of chromatin that can repress or facilitate the expression of genes.
Another epigenetic modification studied in recent years is the methylation of
DNA. Recently it has been observed that there are abnormal patterns of DNA
methylation in many types of cancers. The malignant cells are accompanied by
a global hypomethylation that is associated with the activation of genes
required for the invasion and metastasis and a local hypermethylation (CpG
Islands) associated with the repression of tumor suppressor genes (TSGs).
Thus, the methylation of the TSG blocks its expression, contributing to the
onset and tumor progression. Classic examples are the genes BRCA1, PRC,
TP53 and PRDM in breast, colon, skin and lung cancer, respectively.
The abnormal patterns of DNA methylation, as well as epigenetic
modifications on histones, could be used as biomarkers for the diagnosis of
cancer and as targets of drugs, in order to correct these alterations and restore
the function of the genes. This chapter analyses the current evidence on the
role of epigenetic mechanisms involved in the progression of various types of
cancer and their clinical relevance.
Chapter 3 - The outcomes of pregnancy in patients on dialysis have
greatly improved in the last half-century. Therefore, the current medical
opinion regarding pregnancy in women on hemodialysis has recently changed
from ‘impossible’ to ‘possible,’ and pregnancy is no longer automatically
discouraged, although it is still relatively uncommon and associated with a
certain degree of risk. In order to decide whether to become pregnant or not,
hemodialysis patients and their family members should be provided with
sufficient information regarding the success rate, complications, need of
intensive dialysis 6-7 days per week, optimal nutrition, and alternative options,
including delaying pregnancy to after renal transplantation. In addition, to
avoid delays in the detection of pregnancy, patient education and pregnancy
planning is critical. Hence, close collaboration between patients, their family,
nephrologists, dialysis staff, obstetricians, and neonatologists is necessary.
Chapter 4 - Levonorgestrel (LNG) is a dextrorotatory isomer of the
synthetic progestogen norgestrel. Norgestrel is a racemic mixture. The activity
of norgestrel resides in the dextrorotatory isomer, while the levorotatory
isomer is biologically inactive. Generally, LNG is rapidly absorbed with a
half-life of absorption of less than 1hour. The mean time taken to achieve
maximal serum concentration is less than 2 hours with a bioavailability of over
90%. The half-life of elimination is approximately 24 hours. LNG like other
progestogens not only binds with progesterone receptors but also binds to
other steroid receptors. In conjunction with estradiol, LNG causes anovulation
dependent on the follicular stage and acts as an effective contraceptive agent
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