2020年6月22日 星期一

Researchers Use Lasers to Bring the Internet Under the Sea


Heretofore, attempts to connect to the Internet from under water were all wet. But a team of Saudi technologists have created Aqua-Fi for fast connections beneath the waves.

2020年6月12日 星期五

An animal model of covid-19 is now available

中共幾月前就有所謂動物模式--實驗用於新冠病毒。
問題是差幾個月對疫苗研究有大差別嗎?


Laboratory mice have been genetically engineered to be able to catch the virus

2020年6月11日 星期四

Three big studies dim hopes that hydroxychloroquine can treat or prevent COVID-19


Amid politicization and scandal, a disappointing scientific picture is emerging on hydroxychloroquine, the malaria drug touted as a #COVID19 treatment.

醫學典範轉移 Barry Marshall和Robin Warren 說幽門螺桿菌會引起胃潰瘍而不是壓力和生活方式

2 小時
 
“Everybody knew they were not there, so they couldn’t be there. It was like in the middle ages, everybody knew the earth was flat.”
Robin Warren on discovering bacteria in the stomach and having a difficult time convincing the scientific community about its existence. Initially, no one believed Barry Marshall and Robin Warren when they stated that the bacterium Helicobacter pylori causes stomach ulcers and not stress and lifestyle. They first managed to develop several colonies of the new bacteria in 1982.
Marshall and Warren were awarded the 2005 Nobel Prize. Wishing a happy birthday to Warren who turns 83 today.



“Everybody knew they were not there, so they couldn’t be there. It was like in the middle ages, everybody knew the earth was flat.”
“每個人都知道他們不在那裡,所以他們不可能在那裡。 就像在中世紀,每個人都知道地球是平坦的。” 羅賓·沃倫(Robin Warren)發現胃中的細菌,並且很難說服科學界相信它的存在。 最初,沒有人相信Barry Marshall和Robin Warren當他們說幽門螺桿菌會引起胃潰瘍而不是壓力和生活方式。 他們於1982年首次設法開發出幾種新細菌菌落。
Robin Warren on discovering bacteria in the stomach and having a difficult time convincing the scientific community about its existence. Initially, no one believed Barry Marshall and Robin Warren when they stated that the bacterium Helicobacter pylori causes stomach ulcers and not stress and lifestyle. They first managed to develop several colonies of the new bacteria in 1982.

2020年6月9日 星期二

telomere 端粒



Elizabeth Blackburn discovered the molecular structure of telomeres and co-discovered the enzyme telomerase. Her research offers hope for cancer treatment, clues to the mystery of ageing and even biological links between life circumstance and lifespan.

伊麗莎白·布萊克本(Elizabeth Blackburn)發現了端粒的分子結構,並共同發現了端粒酶。 她的研究為癌症治療提供了希望,為衰老的奧秘提供了線索,甚至為生活環境和壽命之間的生物學聯繫提供了線索。


人類染色體上的端粒
端粒的位置。
人類端粒DNA的四連體結構。圖片來源:NDB UD0017
端粒(英語:Telomere)是真核生物染色體末端的DNA重複序列,作用是保持染色體的完整性和控制細胞分裂週期。 由於DNA複製的機制,每次染色體複製後,延遲股上的染色體末端必無法被複製。[1]因此,真核生物在染色體末端演化出端粒以作為可被重複遺棄的片段。[2]一旦端粒消耗殆盡,細胞將會立即啟動凋亡機制。因此,端粒被推測和細胞老化有明顯的關係。人體的部分細胞,例如精原母細胞癌症細胞等,含有端粒酶,能在DNA末端接上新的端粒片段,其端粒不會隨著分裂次數增加而縮短,因此能無限複製。

概念[編輯]

端粒是存在於真核細胞線狀染色體末端的一小段DNA-蛋白質複合體,它與端粒結合蛋白一起構成了特殊的「帽子」結構,能夠維持染色體的完整和控制細胞分裂週期。
端粒DNA是由簡單的DNA高度重複序列組成的,染色體末端沿著5'到3' 方向的鏈富含 GT。在酵母和人中,端粒序列分別為C1-3A/TG1-3和TTAGGG/CCCTAA,並有許多蛋白與端粒DNA結合。端粒DNA主要功能有:第一,保護染色體不被核酸酶降解;第二,防止染色體相互融合;第三,為端粒酶提供底物,解決DNA複製的末端隱縮,保證染色體的完全複製。端粒、著絲粒和復制原點是染色體保持完整和穩定的三大要素。同時,端粒又是基因調控的特殊位點, 常可抑制位於端粒附近基因的轉錄活性(稱為端粒的位置效應,TPE)。在大多真核生物中,端粒的延長是由端粒酶催化的,另外,重組機制也介導端粒的延長。

發現和歷史[編輯]

  1. 20世紀30年代,Muller發現被X射線打斷的果蠅染色體其末端存在一種特殊序列,該序列與常染色體相較極穩定,故根據希臘文將其命名為「端粒」(Telomere)。
  2. 20世紀70年代,Olovnikov提出假設,認為染色體末端序列的丟失能夠導致細胞退出增殖週期,但並沒有直接證據證實這一假說的成立。
  3. 1978年,Blackburn和Greider等克隆出四膜蟲端粒結構[1],證明為串聯線性核苷酸序列,組成為5′—GGGGGTT —3′。後來實驗又證明了脊椎動物的端粒均含有豐富的鳥嘌呤重複序列。
  4. 1985年,Greider等發現端粒酶,可用於給端粒DNA加尾。

結構[編輯]

端粒(telomere)是由許多成串短的重複序列所組成。該重複序列通常一條鏈上富含G(G-rich),而其互補鏈上富含C(C-rich)。一個基因組內的所有端粒都是由相同的重複序列組成,但不同物種的端粒的重複序列是不同的。


2020年6月5日 星期五

Two elite medical journals retract coronavirus papers over data integrity questions。周前:紐約時報報導. Scientists Question Validity of Major Hydroxychloroquine Study

 

The Lancet and The New England Journal of Medicine today retracted two high-profile papers after a company declined to make the underlying data for both available for an independent audit, following questions being raised about the research.


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Scientists Question Validity of Major Hydroxychloroquine Study

Experts demanded verification of data and methods used in a study of drugs to treat Covid-19. The study suggested the drugs might have increased deaths.




The drug hydroxychloroquine, promoted by President Trump and others in recent months as a possible treatment for people infected with the coronavirus.Credit...George Frey/Reuters



By Roni Caryn Rabin
May 29, 2020


More than 100 scientists and clinicians have questioned the authenticity of a massive hospital database that was the basis for an influential study published last week that concluded that treating people who have Covid-19 with chloroquine and hydroxychloroquine did not help and might have increased the risk of abnormal heart rhythms and death.


In an open letter to The Lancet’s editor, Richard Horton, and the paper’s authors, the scientists asked the journal to provide details about the provenance of the data and called for the study to be independently validated by the World Health Organization or another institution.


A spokeswoman for Dr. Mandeep R. Mehra, the Harvard professor who was the paper’s lead author, said on Friday that the study’s authors had asked for an independent academic review and audit of their work.


Use of the malaria drugs chloroquine and hydroxychloroquine to prevent and treat Covid-19 has been a focus of intense public attention. President Trump has promoted the promise of hydroxychloroquine, despite the absence of gold-standard evidence from randomized clinical trials to prove its effectiveness, and recently said he was taking it himself in hopes of preventing coronavirus infection.



The scientists’ challenges to the Lancet paper come at a time of increasing debate about the risks of the rush to publish new medical findings about Covid-19. The paper, published May 22, included data on tens of thousands of patients hospitalized through April 14, meaning that the authors analyzed the trove of data, wrote the paper and went through the journal’s peer review of its findings in just over five weeks, much faster than usual.


The experts who wrote The Lancet also criticized the study’s methodology and the authors’ refusal to identify any of the hospitals that contributed patient data, or to name the countries where they were located. The company that owns the database is Surgisphere, based in Chicago.


“Data from Africa indicate that nearly 25 percent of all Covid-19 cases and 40 percent of all deaths in the continent occurred in Surgisphere-associated hospitals which had sophisticated electronic patient data recording,” the scientists wrote. “Both the numbers of cases and deaths, and the detailed data collection, seem unlikely.”



Another of the critics’ concerns was that the data about Covid-19 cases in Australia was incompatible with government reports and included “more in-hospital deaths than had occurred in the entire country during the study period.”


A spokeswoman for The Lancet, Emily Head, said in an email that the journal had received numerous inquiries about the paper and had referred the questions to the authors.


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“We will provide further updates as necessary,” she said. “The Lancet encourages scientific debate and will publish responses to the study, along with a response from the authors, in the journal in due course.”




Dr. Sapan S. Desai, the owner and founder of Surgisphere and one of the paper’s authors, vigorously defended the findings and the authenticity and validity of the company’s database. He said official counts of coronavirus cases and deaths often lagged behind actual cases, which might explain some discrepancies.


The paper’s authors said they had analyzed data gathered from 671 hospitals on six continents that shared granular medical information about nearly 15,000 patients who had received the drugs and 81,000 who had not, while shielding their identities.


“What the world has to understand is that this is registry-based data,” Dr. Desai said. “We have no control over the source of the information. All we can do is report the data that is given to us.”


Another group of researchers from the Barcelona Institute for Global Health also raised questions about the Surgisphere database, both with the authors and editors of The Lancet.


Scientists who wrote and signed the letter criticizing the study included clinicians, researchers, statisticians and ethicists from academic medical centers, including Harvard’s T.H. Chan School of Public Health, the University of Pennsylvania, Vanderbilt University and Duke University.



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One of the signatories, Dr. Adrian Hernandez, who heads the Duke Clinical Research Institute, said the paper contained many troubling anomalies, “but the biggest thing that raised a red flag was that here was such a large database across more than 600 hospitals, and no one had really known about its existence. That was quite remarkable.”



Like several other signatories of the letter, Dr. Hernandez is involved in a clinical trial of hydroxychloroquine to see if it can protect health care workers from infection.

The Coronavirus Outbreak
Today’s Question: My state is reopening. Is it safe to go out?

States are reopening bit by bit. This means that more public spaces are available for use and more and more businesses are being allowed to open again. The federal government is largely leaving the decision up to states, and some state leaders are leaving the decision up to local authorities. Even if you aren’t being told to stay at home, it’s still a good idea to limit trips outside and your interaction with other people.


Allen Cheng, a professor of infectious diseases at Monash University in Melbourne, Australia, who also signed the letter, said in an email that the individual hospitals included in the database should be identified.


“Ideally, the database should be made public, but if that isn’t possible, it should at least be independently reviewed and an audit performed,” he said.


Surgisphere’s data was also the basis of a study of coronavirus patients published in The New England Journal of Medicine this month by some of the same authors, including Dr. Desai and Harvard’s Dr. Mehra, as well as for two versions of an article on the use of an antimicrobial drug to treat Covid-19 that were not published in an established medical journal.


Jennifer Zeis, a spokeswoman for The New England Journal of Medicine, said by email that the journal was aware of the questions that had been raised and was looking into them.


Dr. Mehra issued a statement Friday, saying that the paper’s authors “leveraged the data available through Surgisphere to provide observational guidance to inform the care of hospitalized Covid-19 patients” because the results of randomized clinical trials would not be available for some time.


Other observational studies had previously reported possible harms associated with the malaria drugs, and the Food and Drug Administration had issued a safety warning about their use. After the Lancet paper was published, the World Health Organization and other organizations suspended clinical trials of the drugs.