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Discovery of Sperm and Egg -- and Their Role in Reproduction

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发表于 6-12-2017 15:18:06 | 显示全部楼层 |阅读模式
本帖最后由 choi 于 6-12-2017 15:46 编辑

The article is locked behind paywall.

Laura J Snyder, The Birth of Wisdom; It wasn't until recently—the late 1800s—that we knew for sure where babies come from. Wall Street Journal, July 3, 2017.
https://www.wsj.com/articles/the-birth-of-wisdom-1496435934
(book reviews on Edward Dolnick, The Seeds of Life; From Aristotle to da Vinci, from Sharks' Teeth to Frogs' Pants, the long and strange quest to discover where babies come from. Basic Books, 2017)

Note:
(a) "On an autumn night in 1677, a Dutch civil servant ['chamberlain for the assembly chamber of the Delft sheriffs in the city hall,' Delft being the city he was born and lived: wn.wikipedia.org] named Antoni van Leeuwenhoek rose from his bed immediately after intercourse with his wife [second wife Cornelia Swalmius, whom he married in 1671 after the death of the first wife in 1666]. He rushed to his study, lit a candle and examined a drop of his semen with his microscope" -- he was the first to discover sperms.
(i) Van Leeuwenhoek. Behind the Name, undated
https://surnames.behindthename.com/name/van00leeuwenhoek
("Literally means 'from lion's corner.' The first bearer of this name lived on the corner (hoek in Dutch) of the Lion's Gate (Leeuwenpoort in Dutch) in the city of Delft (in the province of Zuid-Holland), which eventually resulted in Leeuwenhoek as a surname. A famous bearer of this surname is Antonie van Leeuwenhoek (1632-1723), a pioneer in the field of microscopy")
(ii) Dutch-English dictionary:
* hoek (noun masculine; plural hoeken): "corner"
https://en.wiktionary.org/wiki/hoek
* leeuw (noun masculine; plural leeuwen): "lion"
https://en.wiktionary.org/wiki/leeuw
* poort (noun feminine and masculine; plural poorten; from Latin [noun feminine] porta [gate, especially of a city]): "gate"
https://en.wiktionary.org/wiki/poort
(iii) "Leeuwenpoort (Lion's Gate), also long gone": from the Web
(iv)
(A) The most famous Lion's Gate is
Lion Gate
https://en.wikipedia.org/wiki/Lion_Gate
(still at Mycenae)
(B) Mycenae
https://www.merriam-webster.com/dictionary/Mycenae


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 楼主| 发表于 6-12-2017 15:19:35 | 显示全部楼层
(b) "The ancients had wondered about reproduction, of course. Aristotle opened up fertilized chicken eggs at intervals to observe the development of the embryos and mused that human embryos underwent the same kind of transformation. He believed that a human baby was initially formed from the man's semen being 'curdled' by the women's menstrual blood, 'the same way,' he asserted, 'as rennet acts upon milk' to form cheese.
(c) "In the early 1500s men began [dissecting dead bodies] * * * 'At the same time he was painting the Mona Lisa,' we learn [from this book], 'Leonard was cutting open the faces of corpses and dissecting the muscles of the mouth and lips, to sort out the secrets of the smile.'  This was the opening salvo of the Scientific Revolution. * * * By the middle of the 1600s the English Physician William Harvey, who discovered that the heart is a pump circulating blood around the body, was arguing all mammals, including humans, came from eggs inside the mother. 'Ex ovo omnia,' became his motto: 'Everything comes from the egg.' But what he had seen during the dissections were not eggs, only small clusters of cells making up early-stage embryos in the uterus.

(d) "In 1672, Regnier de Graaf, a Dutch physician, sliced open rabbits at increasing intervals after copulation. He used a microscope to watch eggs burst out of the ovary; soon afterward, tiny embryos appeared in the uterus. * * * What he observed
(i) That account is untrue, about "egg" and "microscope" -- he did not see eggs, because he did not have, but was aware of development of, a microscope.

"A few months before his death [in 1673] De Graaf recommended, as a correspondent of the Royal Society in London, that attention be paid to Antonie van Leeuwenhoek [both lived in the same city: Delft] and his work on the improvement of the microscope."
https://en.wikipedia.org/wiki/Regnier_de_Graaf
(ii) The following account is historically correct.

Ellen M Dupont, Regnier de Graaf (1641-1673). In The Embryo Project Encyclopaedia. Arizona State University, Sept 30, 2008
https://embryo.asu.edu/pages/regnier-de-graaf-1641-1673
("de Graaf's research was plagued by several misconceptions stemming mostly from the lack of microscopic equipment at the time.  Interestingly, all de Graaf's work took place more than 150 years before Karl Ernst von Baer first identified the ovum [another scientific term is 'oocyte'] in 1827. * * * De Graaf deduced its existence from his knowledge of ectopic (tubal) pregnancies, and he was aware of the unidentified object's [the unidentified object is a fertilized egg, or zygote] path of travel. However, he mistakenly believed that the egg actually consisted of the [mature] ovarian follicle [which is quite big to be observed with naked eye] itself, which he thought detached from the ovary and entered the Fallopian tube. Though de Graaf's theory was incorrect, he did realize that the structure traveling down the Fallopian tube [also known as oviduct] was significantly smaller than the supposed parent follicle, an inconsistency he was never able to explain. With the help of highly improved microscopic equipment, future scientists would reveal that the Graafian follicles actually rupture, releasing the mature egg into the tube. * * * Among de Graaf’s notable accomplishments was his comparison of pre- and post-mating ovaries; the structural differences he noted led to his realization of the morphological changes that accompany the ovary's functioning"
(iii)
(A) The Dutch surname de Graaf: "from graaf count (see [German surname] Graf), with the addition of the definite article de"
(B) Dutch-English dictionary:
* graaf (noun masculine): "earl, count"
https://en.wiktionary.org/wiki/graaf
(iv) Karl Ernst von Baer
https://en.wikipedia.org/wiki/Karl_Ernst_von_Baer
(was born into a Baltic German noble family of Russian Empire, in present-day Estonia)
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 楼主| 发表于 6-12-2017 15:20:21 | 显示全部楼层
(e) "Once Leeuwenhoek saw sperm, he was convinced that eggs played no role in conception. Instead, he believed the sperm burrowed into the uterus and grew into babies -- just as apple seeds [;aced in the ground sprouted into trees.

(f) "In one notable experiment of 1770s, an Italian [Catholic] priest named Lazzaro Spallanzani made tiny pants for male frogs that would prevent their semen from reaching the female's egg, which she [female frog] deposits outside her body during mating. Eggs from females who had mated with the pants-clad males never developed into frogs, proving that eggs alone were not enough for reproduction: Semen was required as well. Two later research further showed that the crucial; element in semen was the sperm."

Try as I may, I fail to find what the pants designed by Lazzaro Spallanzani looked like. It must have been able to prevent leaks.

(g) "The advent of cell theory finally brought the egg-sperm dispute to a close. * * * in 1875, nearly 200 years after Leeuwenhoek. Zoologist Oscar Hertwig was studying sea-urchin eggs fished up from the Bay of Naples. He placed one of the transparent eggs under his microscope, where the nucleus was clearly visible. Poking a drop of sea=urchin semen near the egg, he watched as a tiny sperm cell pushed itself inside and wriggled toward the nucleus.  'Suddenly,' Mr Dolnick writes, 'the two nuclei were in contact, and then before Hertwig's eyes -- the two nuclei fused into one.' "
(i) Oscar Hertwig
https://en.wikipedia.org/wiki/Oscar_Hertwig
(German; By studying sea urchins he proved that fertilization occurs due to the fusion of a sperm and egg cell)
(ii) The German (Hartwig also Härtwig; variant: Hertwig), Dutch (Hartwig), and Danish (Hartvig) surnames: "from a Germanic personal [ie, given] name composed of the elements hard hardy, strong + wig battle, combat"
Dictionary of American Family Names, by Oxford University Press.
(iii) nucleus (n; etymology: because it is Latin, its plural form is nuclei)
https://www.merriam-webster.com/dictionary/nucleus
(iv)
(A) sea urchin (inhabit all oceans; The name "urchin" is an old word for hedgehog, which sea urchins resemble; having separate male and female sexes; "Regular sea urchins have five gonads * * * Each gonad has a single duct rising from the upper pole to open at a gonopore * * * surrounding the anus [or mouth; a sea urchin has just one opening]. The gonads are lined with muscles [so as to] squeeze its gametes through the duct" into the sea; The transparency of of the urchin's eggs enabled them to be used to observe that sperm cells actually fertilize ova)  en.wikipediqa.org

Gametes. In Sea Urchin Embryology. Stanford University, undated
https://seaurchineducation.stanford.edu/p-gametes

"FOR COMPARISON:

• hydrogen atom is 0.0001 microns
• globular protein is 0.004 microns
• large virus us 0.1 micron
• E. coli bacteria is 2 microns
• Sea urchin and human sperm w/o [without] tail is 1x5 microns
• Human red blood cell is 9 microns
• somatic cells are 10-30 microns
• amoeba is 90 microns
• sea urchin and human egg is 100 microns
• frog egg is 2000 microns [or 2mm]"

"Males: sperm [the correct English word is 'milt,' which is equivalent to 'semen' in humans] are a milky white color

"Females: eggs are pale yellow to orange to dark maroon depending on species." [This is the color of egg cytoplasm 细胞质. As one can see from a diagram in this Web page, the nucleus is a tiny portion of the egg.]

(B) The preceding Web page does not explain what potassium chloride injection is for. For this see
Sea Urchin Embryology Lab. by Center for Cell Dynamics, University of Washington, undatedrusty.fhl.washington.edu/celldynamics/downloads/methods/urchinlab.html
http://rusty.fhl.washington.edu/ ... hods/urchinlab.html
("How to get gametes from sea urchins [which is sectional heading:] The most common method is to inject potassium chloride (KCl) into the body cavity [of sea urchin]. * * * *KCl stimulates the gond wall to contract; ripe gametes emerge from the gonopores surrounding the anus on the aboral (up) side of the animal")
(v) "before Hertwig's eyes -- the two nuclei fused into one"

The term "nuclei" is technically wrong. Hours after a sperm enters an egg, the sperm head turns round. At this stage, both male and female nuclei {each enclosed by a membrane) are called pronuclei (which is plural of 'pronucleus' "). The pronuclei moved slowly toward each other and in sea urchin, the membranes of the 2 pronuclei fuse. Not in mammals, where the membranes of the 2 pronuclei, when they come close, simply dissolve. See
Fertilization. In Alberts B et al, Molecular Biology of the Cell. 4th ed. New York: Garland Science, 2002.
https://www.ncbi.nlm.nih.gov/books/NBK26843/
("In fertilized mammalian eggs, the two pronuclei do not fuse directly as they do in many other species. They approach each other but remain distinct until after the membrane of each pronucleus has broken down in preparation for the zygote's first mitotic division")

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