China
Africa
Explore chapters and articles related to this topic
Heterologous Pairing and Fertility in Humans
Published in Christopher B. Gillies, Fertility and Chromosome Pairing: Recent Studies in Plants and Animals, 2020
Translocations involving acrocentrics — Human translocations involving acrocentric chromosomes, compared with those that do not, lead to increased germ cell death. Gabriel-Robez et al.133 have shown a ratio of 1:4 for translocations with an acrocentric present, compared with nonacrocentric translocations in fertile males. This ratio changes to 1:1 in patients ascertained through subfertility. In what way might acrocentric chromosomes bring about this change? In normal males, it has been observed that the heterochromatic short arm regions of the D- and G-group acrocentrics which also carry the nucleolar organizer region associate with the sex vesicle.134,135 It has already been shown that asynaptic regions in translocation quadrivalents associate with the XY bivalent. The further presence of acrocentric elements with an added affinity for the sex chromosomes may enhance cell disruption. Table 4 presents the available data on human translocations involving acrocentrics, and those which do not, and their levels of association with the XY bivalents seen at pachytene. Although not all authors present accurate sperm counts or details of testicular histology for translocations involving acrocentrics, increased quadrivalent/XY association is suggestive of increased levels of fertility disturbance, as reflected in the lowered sperm count.
rDNA: Evolution Over a Billion Years
Published in S. K. Dutta, DNA Systematics, 2019
The DNA in X. laevis can be divided into chromosomal and extra-chromosomal rDNA. The chromosomal rDNA consists of 450 to 800 tandemly repeated gene units which occur in the nucleolar organizer region.158,159 Using in situ hybridization Pardue160 confirmed the location of rDNA in the secondary constrictions of the largest subtelocentric pair of chromosomes. In addition to the normal occurrence of two nucleolar organizers, individuals heterozygous (1-nu) and null (o-nu) for the nucleolar organizers are known and have been used in developmental studies.161–163,429 Although development is retarded in anucleolate individuals,161 rRNA synthesis proceeds normally in individuals which have greatly reduced, but not totally depleted, copies of rRNA genes.164 The lack of reduced rRNA synthesis during development is in part due to the presence of extrachromosomal copies of rDNA found in the oocyte. Extrachromosomal rDNA is amplified approximately 1000-fold in the oocyte and these copies are active only during oogenesis, thus enhancing the synthesis of rRNA during this stage of development.165
Barbara McClintock (1902–1992)
Published in Krishna Dronamraju, A Century of Geneticists, 2018
She showed that the loss of ring-chromosomes at meiosis caused variegation in maize foliage in generations subsequent to irradiation resulting from chromosomal deletion. During this period, she demonstrated the presence of the nucleolus organizer region on a region on maize chromosome 6, which is required for the assembly of the nucleolus.
The biological effects of electromagnetic exposure on immune cells and potential mechanisms
Published in Electromagnetic Biology and Medicine, 2022
Chuanfu Yao, Li Zhao, Ruiyun Peng
Several studies showed that electromagnetic exposure could produce inhibitory effects on immune cells. Xu et al. (1998) investigated the staffs of communication station and found that shortwave exposure at average electric field strength of 57 V/m significantly reduced peripheral blood leukocytes. Compare to the control group, the CD3+ T lymphocytes was down-regulated and the abnormal ratio of CD4+/CD8+ occurred much more frequently, indicating that long-term exposure to shortwave exposure could induce immune suppression. Yin and Zhang (2005) showed that the level of argyrophilic protein in the nucleolus organizer region (NOR) decreased obviously in T lymphocytes from the peripheral blood of the workers, who were long-term exposed to high power microwave (HPM) with an average power density of 0.125 mW/cm2, suggesting immune activity of T lymphocytes was inhibited. Moreover, Boscol et al. (2001) investigated the effects of electromagnetic exposure with frequency ranging from 500 kHz to 3 GHz and at average electric field strength of 4.3 ± 1.4 V/m, which was generated by radio and television stations, on women’s immune cells. Immune suppression could be detected in peripheral blood of related practitioners, for example, the number of CD16+CD56+ NK cells and CD3+CD8+ cytotoxic T lymphocytes (CTLs) was significantly decreased.
DC-CIK as a widely applicable cancer immunotherapy
Published in Expert Opinion on Biological Therapy, 2020
Shuo Wang, Xiaoli Wang, Xinna Zhou, Herbert Kim Lyerly, Michael A. Morse, Jun Ren
The role of checkpoint blockade in breast cancer has been limited thus far to the triple negative subtype (TNBC), perhaps explained by the greater T cell infiltration in TNBC [24]. This supports interventions such as DC-CIK intended to increase T cell infiltration of tumors. In a review of CIK alone, DC alone and DC-CIK in the treatment of breast cancer patients [25], the 1-year overall survival rate of the 633 patients was significantly improved in the DC-CIK group (P = 0.0001). Compared with control group, the DC-CIK treatment group was noted to have significantly greater peripheral blood CD3 + T cell, CD4 + T cells, CD8 + T cells, natural killer T cells (CD56+ CD16+ cells) (P < 0.05). The levels of IL-2, IL-12, TNF-α, IFN-γ, and nucleolar organizer region protein in the peripheral blood were also significantly increased in the DC-CIK group.
Repurposing Natural Dietary Flavonoids in the Modulation of Cancer Tumorigenesis: Decrypting the Molecular Targets of Naringenin, Hesperetin and Myricetin
Published in Nutrition and Cancer, 2022
Carolina Sousa, Denise Duarte, Beatriz Silva-Lima, Mafalda Videira
In anaplastic thyroid cancer, treatment with HESP decreased cellular proliferation in a time- and dose-dependent trend with an incremented Notch one expression and its downstream effectors (Hey-1 and Hes-1), as well as pro-apoptotic proteins, such as caspase-3 and Bad (11) (Figure 2). Sheokand et al. (74) observed a significant decrease in breast tumor formation and size, as well in PCNA (Proliferating Cell Nuclear Antigen) levels and AgNOR (Argyrophilic Nucleolar Organizer Region) counts in the nucleus, reveling the anti-proliferative effect of this flavonoid by targeting two important cancer markers (74, 75) (Table 2).