曾鼎 and 刘璐, 百亿保健帝国权健,和它阴影下的中国家庭. 丁香医生, Dec 25, 2018.
(a) 微信: https://mp.weixin.qq.com/s/J5XA3K5PcOEsgs6czE0nlg
(b) Web: https://dxy.com/column/21773
PDQ Pediatric Treatment Editorial Board, Childhood Extracranial Germ Cell Tumors Treatment (PDQ®). In PDQ Cancer Information Summaries. PDQ, Dec 13, 2018 ("health professional version")
https://www.ncbi.nlm.nih.gov/books/NBK65877/
Note:
(a) "Most childhood extragonadal GCTs arise in midline sites (ie, head and neck, sacrococcygeal, mediastinal, and retroperitoneal); the midline location may represent aberrant embryonic migration of the primordial germ cells."
Heed the word "aberrant": Normally (all) "primordial germ cells (PGC)” and its progeny (germ cells), in embryology 胚胎学 (of all animals, from worms to humans), migrate to the "gonadal ridge;" together they form the future gonads. When aberrant migration of germ cells occurs, they later form extragonadal germ cell tumor (GCT), which seems invariably in the midline (from inside the brain down to tip of spine) -- of course gonadal GCT (in a testis or ovary) are not in the midline. As of the present: In humans (as well as mice), how PGC makes normal migration is unknown; in ALL animals, why and how aberrant migration of PGC occurs are unknown.
(i) normal development of PGC (and therefore, sex differentiation).
(A) Nikolic A et al, Primordial Germ Cells: Current Knowledge and Perspectives. Stem Cell International, 2016: 1-8.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4655300/
Quote (citations omitted):
"Germ cells undergo two significantly different developmental phases. The first phase occurs during early embryogenesis, when primordial germ cells (PGCs) are formed and actively migrate to the gonadal ridge. In the second phase, the germ cells receive appropriate signals from their environment and initiate one of two distinct programs of controlled cell division, meiosis, and differentiation-oogenesis or spermatogenesis, to form gametes. The molecular basis of both processes and early germ cell development is very well understood in two species, Drosophila 果蝇 and Caenorhabditis elegans [a worm of 1 mm in length], where systematic genetic reviews have identified many of the genes required in this process. PGCs in humans have not been intensely investigated because of the technical and ethical obstacles to obtaining such cells from early embryos. The greater part of our knowledge of mammalian PGC specification has been obtained from studies using early mouse embryos" (The review then talked about what genes were involved in PGC migration and development in Drosophila and C elegans, but you need not know these.)
"In contrast to D melanogaster and zebrafish, little is known about PGC migration and initiation of that process in mice.
(B) Naturally it is difficult to imagine what the first part of quotation in (a)(i)(A) means. Graphics will help.
Rey R et al, Sexual Differentiation. In EndoText (an e-book), last updated June 12, 2016.
https://www.ncbi.nlm.nih.gov/books/NBK279001/
, where Figure 1 was about "(A) 4-week embryo" and "(B) 5-week embryo." The author neglected to say what animal it was. Well, it is human. Mouse (especially the one we use in labs) gestation lasts 20 days. Caption of the figure listed limited number of genes that were involved. Again you need not know more.
In both (A) and (B), the embryo itself was colored brown. (A) showed the lateral view of the embryo (placed horizontally, with head at the left), whereas (B) the oblique view 9of an embryo placed vertically whose bottom half only was sketched).
(C) Richardson BE and Lehmann R, Mechanisms Guiding Primordial Germ Cell Migration: Strategies from Different Organisms. Nature Reviews Molecular Cell Biology ("Nature Reviews" has many topics; this is in molecular and cell biology), 11: 37-49 (2010).
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4521894/
("The study of how cells migrate is highly relevant to our understanding of both normal and pathological processes. * * * In many animals the primordial germ cells (PGCs), precursors to sperm and eggs, arise far from the somatic cells of the developing gonad (somatic gonadal precursors (SGPs)) and therefore have to actively migrate across the embryo to reach their site of function. This process provides a useful model system for the study of cell migration within the context of a developing organism. PGC migration must be finely regulated as it follows a complex path through a variety of developing tissues. In addition to the obvious effect of disrupted PGC migration on fertility, aberrant movement to ectopic sites in the body is one mechanism that could account for the incidence of extragonadal germ cell tumours in humans. Most of our understanding of PGC migration comes from the model genetic organisms Drosophila melanogaster, zebrafish and mice. * * * The general events of PGC migration in model organisms have been well characterized (discussed below; FIG 1). Although there are important differences in the specification and migration of PGCs in these organisms, there are also several shared principles emerging")
The "neural tube" (colored blue) in FIG 1 is the precursor of central nervous system (brain and spinal cord).
In both (a)(i) (B) and ©, you can see that germ cells (undifferentiated; can be developed into either male or female cells) migrate caudally (toward the tail). Thus it is impossible to know (for anybody in the world) that these cells might be possibly migrate to brain, neck or mediastinum (the space between lungs, above heart and below neck) -- but germ cell tumors in these latter locations are extremely rare. See next.
(ii) Childhood Central Nervous System Germ Cell Tumors Treatment (PDQ®). undated (health professional version)
https://www.cancer.gov/types/bra ... -cell-treatment-pdq
(read the section "Anatomy" and view the accompanying figure)
(A) "The pineal gland [松果腺] produces melatonin * * * a hormone which modulates sleep patterns in both circadian and seasonal cycles. The shape of the gland resembles a pine cone from which it derived its name." en.wikipedia.org for "pineal gland."
(B) melatonin
https://www.etymonline.com/word/melatonin
("it changes the skin color of certain reptiles and amphibians")
In terms of chemical structure, melatonin and melanin 黑色素 are from different categories.
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