Dear visitors! We had been in a discussion since too long that there was a mythical creature chimeras present which was a Lion-Goat-Serpent Monster. According to the BBC news scientists have tried to develop an embryo with the cells of more than one species. It is necessary to note here that fertilization can never occur between the gametes of two different species so scientists injected the stem cells of human into the pig embryo. For more information I would like to copy the article of "James Galleger" from BBC website.
[It is the first proof chimeras - named after the mythical lion-goat-serpent monster - can be made by combining material from humans and animals.
However, the scientific report in the journal Cell shows the process is challenging and the aim of growing human organs in animals is distant.
It was described as an "exciting publication" by other researchers.
To create a chimera, human stem cells - the type that can develop into any tissue - are injected into a pig embryo.
Image caption
The spherical pig embryo is held in place while a tiny needle is used to inject human cells
The embryo - now a mix of human and pig - is then implanted into a sow for up to one month.
The process appears very inefficient - of the 2,075 embryos implanted only 186 continued to develop up to the 28-day stage.
But crucially there were signs that human cells were functioning - albeit as a tiny fraction of the total tissue - as part of a human-pig chimera.
"This is the first time that human cells are seen growing inside a large animal," Prof Juan Carlos Izpisua Belmonte, from the Salk Institute, told the BBC News website.
Image caption
Human cells, coloured green, were found in the four-week-old embryo
Commenting on the inefficiency, Prof Belmonte said: "Humans and pigs are separated by a long time in evolution."
Development in the womb is also much faster in pigs - pregnancy lasts less than four months compared with about nine in people.
"It is like a freeway with one car going much faster than another - you're more likely to have an accident," Prof Belmonte said.
He added there was a "long distance" between now and growing animals with human organs - such as a heart, pancreas or liver, that can be transplanted.
However, in the meantime the Salk researchers argue that making chimeras with more human tissue could be useful for:
screening drugs before human trials
studying the onset of human diseases
understanding the earliest stages of human embryo development.
explaining differences between organs in different species
Dr Jun Wu, part of the research team, told the BBC: "[Getting the efficiency] in the range of 0.1% to 1% human cells should be enough.
"Even at this early stage [28-days], billions of cells in the embryo would have millions of human cells, then testing would be meaningful and practical."
There was no evidence that human cells were integrating into the early form of brain tissue.
Organ breakthrough
On Wednesday, a study in the journal Nature showed how organs could be grown in one species for use in another: by making some room.
Rats were genetically modified so they could not produce a pancreas - the organ crucial for controlling blood sugar levels.
Mouse stem cells were injected in the deficient rat embryos, promptly took advantage of the missing pancreas and grew a mouse one there instead.
This was then transplanted back into mice to treat diabetes.
The work to try this in humans and pigs is already under way.
Although in the long term cows look likely to be a better host for human organs as both cow and human pregnancies last about nine months.
The field is also ethically charged, the US National Institutes of Health at one point imposed a moratorium on funding the experiments.
The researchers have done only research that is legal, but they are aware of the controversy.
Prof Belmonte said: "We are restricting development to one month in the pig, the reason is this is enough for us now to understand how cells mix, differentiate and integrate.
"One possibility is to let these animals be born, but that is not something we should allow to happen at this point.
"Not everything that science can do we should do, we are not living in a niche in lab, we live with other people - and society needs to decide what can be done.
Dr Wu said: "When the public hears the world chimera it is always associated with Greek mythology, there is always this associated fear.
"But angels are chimeras, it can be a positive image and hopefully help with a worldwide shortage of organs, not create a monster."
Image caption
Chimeras are named after the fire-breathing beast of Greek mythology
Prof Bruce Whitelaw, the interim director of the Roslin Institute where Dolly the sheep was cloned, said: "This is an exciting publication.
"It clearly demonstrates that human stem cells introduced into the early pig embryo can form a human-pig chimera.
"This is the first scientific publication to achieve this result.
"This is a first in the development of chimeric animal production and paves the way for significant advances in our understanding of development in the embryo and hints towards future novel biotech applications."
Prof Robin Lovell-Badge, from the Francis Crick Institute, said: "An ability to make interspecies chimeras would be valuable in terms of providing basic understanding of species differences in embryo development and organ function.
"It would also offer the possibility of growing human tissues or organs in animals for transplants - although this is still a long way off.
"The goals of this study are therefore highly laudable."]
Thursday, January 26, 2017
Pig-Human Embryo
Facts about Human Heart
1. The “thump-thump” of a
heartbeat is the sound made by the
four valves of the heart closing.
2. The heart does the most physical work of any muscle during a lifetime. The power output of the heart ranges
from 1-5 watts. While the quadriceps can produce 100 watts for a few minutes, an output of one watt for 80
years is equal to 2.5 gigajoules.
3. The heart begins beating at four
weeks after conception and does not stop until death.
4. A newborn baby has about one
cup of blood in circulation. An adult human has about four to five quarts which the heart pumps to all the tissues and to and from the lungs in about one minute while beating 75 times.
5. The heart pumps oxygenated
blood through the aorta (the largest artery) at about 1 mile (1.6 km) per hour. By the time blood reaches the capillaries, it is moving at around 43 inches (109 cm) per hour.
Facts you should know
Hello friends and dear students here are some biological facts....
Have a look...
1. Fingernails grow four times faster than toenails
2. Right handed people live, on average, nine years longer than left-handed people
3. If you rub an onion on your foot – within 30 – 60 minutes you will be able to taste it – this is because it travels through the blood stream
4. You can’t kill yourself by holding your breath (if you hold it until you go unconscious, you begin to breath normally as soon as you do)
5. On one square inch of human skin there are 20 million microscopic creatures
6. Armadillos are the only creatures apart from men that can catch leprosy – there are known cases of armadillo to human transfers of the disease
7. A snail can sleep for 3 – 4 years – during which period it does not need food
8. Giraffes can live longer without water than camels
9. The songs of humpback whales can change dramatically from year to year, yet each whale in an oceanwide population always sings the same song as the others
10. The forces required to remove a foot from quicksand at a speed of one centimeter per second would require the same amount of force as “that needed to lift a medium-sized car.”
11. To test if a pearl is real, you can rub vinegar on it – the composition of the pearl will cause it to bubble furiously
12. Goldfish kept in a dark room turn much paler – and if it wasn’t for the color in the food they eat, they would turn completely white
13. Unlike normal bees, the Queen bee’s stinger is not barbed and can be used repeatedly without harming her
14. Quicksand doesn’t directly kill humans as it is usually not very deep at all – it is the fact that it can be incredibly difficult to remove yourself from quicksand that causes death by the environment – such as exposure.
15. Oysters can change between being female or male
Effect of Inhalers on children
This research article was published in online magazine "Science daily" on 16th july 2014
Corticosteroid drugs that are given by inhalers to children with asthma may suppress their growth, evidence suggests. Two new systematic reviews published in The Cochrane Library focus on the effects of inhaled corticosteroid drugs (ICS) on growth rates. The authors found children's growth slowed in the first year of treatment, although the effects were minimised by using lower doses.
Inhaled corticosteroids are prescribed as first-line treatments for adults and children with persistent asthma. They are the most effective drugs for controlling
asthma and clearly reduce asthma deaths, hospital visits and the number and severity of exacerbations, and
improve quality of life. Yet, their potential effect on the growth of children is a source of worry for parents and
doctors. Worldwide, seven ICS drugs are currently available: beclomethasone, budesonide, ciclesonide, flunisolide, fluticasone, mometasone and triamcinolone. Ciclesonide, fluticasone and mometasone are newer and
supposedly safer drugs. The first systematic review focused on 25 trials involving 8,471 children up to 18 years old with mild to moderate persistent asthma. These trials tested all available
inhaled corticosteroids except triamcinolone and showed that, as a group, they suppressed growth rates when compared to placebos or non-steroidal drugs. 14 of the trials, involving
5,717 children, reported growth over a year. The average growth rate, which was around 6-9 cm per year in control groups, was reduced by about 0.5 cm in treatment groups. "The evidence we reviewed suggests that children treated daily with inhaled corticosteroids
may grow approximately half a centimetre less during the first year of treatment," said lead
author of the review, Linjie Zhang, who is based at the Faculty of Medicine at the Federal University of Rio Grande in Rio Grande, Brazil. "But this effect is less pronounced in subsequent years, is not cumulative, and seems minor compared to the known benefits of the drugs for controlling asthma and ensuring full lung growth."
In the second review, the same authors, working with two others, reviewed data from 22 trials in which children were treated with low or medium doses of inhaled corticosteroids. These trials tested different doses of all drugs except triamcinolone and flunisolide. Only
three trials followed 728 children for a year or more, with one of these trials testing three different dosing regimens. In the three trials, using lower doses of the inhaled corticosteroids, by about one puff per day, improved growth by a quarter of a centimetre at one year.
The researchers found that growth suppression varied across studies, and so they looked at
the relationship between a variety of factors and their effects on growth. Some of the
variation could be explained by the drugs used, although since this was an indirect
comparison the authors say more evidence is needed. "Conclusions about the superiority of
one drug over another should be confirmed by further trials that directly compare the drugs,"
said Zhang.
More long-term trials and trials comparing different doses are also needed, particularly in
children with more severe asthma requiring higher doses of inhaled corticosteroids, the
researchers conclude. "Only 14% of the trials we looked at monitored growth in a systematic
way for over a year. This is a matter of major concern given the importance of this topic,"
said Francine Ducharme, one of the authors of both reviews and senior author of the second
review, based at the Department of Paediatrics at the University of Montreal in Montreal,
Canada. "We recommend that the minimal effective dose be used in children with asthma
until further data on doses becomes available. Growth should be carefully documented in all
children treated with inhaled corticosteroids, as well in all future trials testing inhaled
corticosteroids in children."
Ebola.....The threat
Replication of Ebola Virus published in "MICROBIOLOGY INFO AND NOTES"
Nov 23rd, 2014 Edition·
Replication of Ebola Virus
Ebola Virus do not replicate through any kind of cell
division; rather, they use a combination of host and
virally encoded enzymes, alongside host cell
structures, to produce multiple copies of viruses.
These then self-assemble into viral macromolecular
structures in the host cell. The virus completes a set
of steps when infecting each individual cell.
Following are the steps during the replication of
Ebola Virus :
1. Attachment
First of all, there is attachment of virus to host
receptors through GP glycoprotein which is
endocytosed into vesicles in the host cell. Host DC-
SIGN and DC-SIGNR play a role in virion attachment.
2. Viral Entry (Penetration)
The virion enters early endosomes by
Macropinocytosis or clathrin-mediated endocytosis.
A. Macropinocytosis
In this process, ruffled segments of the host’s
plasma membrane protrude outward from the cell and
form invaginations where the virus utilizes
glycoproteins in order to attach to the surface of the
plasma membrane. Macropinocytosis is a process in
which the Eukaryotic host cells form
macropinosomes, segments of plasma membranes
that extend out from the cell approximately 0.2-10
µm, in order to incorporate the virus into the cell. The
formation of macropinosomes occurs spontaneously,
as a result of the activation of various growth factors,
or simultaneously with the intake of cellular
molecules or extracellular fluid.
B. Clathrin-mediated endocytosis
Clathrin-mediated endocytosis is the other means by
which Ebolavirus enters the host cell. This process is
very similar to macropinocytosis in that the plasma
membrane forms invaginations that engulf the cell.
However, clathrin-mediated endocytosis is different
in that proteins on the surface of the host’s surface,
and in particular clathrin, facilitate the attachment of
the virus to the host’s cell surface. Glycoproteins are
still used to attach the virus to the cell surface, and
the NP-C1 cholesterol transporter still facilitates the
fusion of the virus with endosomes and lysosomes
and still allows the virus to escape into the
cytoplasm. Without the NPC1 cholesterol transporter,
Ebolavirus cannot leave the vesicle in order to
replicate and cause infection in other cells.
To penetrate the cell, the viral membrane fuses with
vesicle membrane, and the nucleocapsid is released
into the cytoplasm.
In some culture cells, GP glycoprotein can be
processed by host Cathepsin L andCathepsin B into
19kDa GP1. But this processing is not happening in
all cells or for all ebolavirus. 19kDA GP1 interacts
with host NPC1, which is highly expressed in
dendritic cells.
Fusion of virus membrane with the vesicle
membrane is triggered by either low pH orNPC1
binding.
3. Sequential Transcription
During transcription, the RNA genome is transcribed
into seven monocistronic mRNAs whose length is
determined by highly conserved start and stop
signals.
The transcription process begins with the binding of
the polymerase complex to a single binding site
located within the leader region of the genome. The
complex then slides along the RNA template and
sequentially transcribes the individual genes in their
3’ to 5’ order. Encapsidated, negative-sense genomic
ssRNA is used as a template for the synthesis (3′-5′)
of polyadenylated, monocistronic mRNAs and, using
the host cell’s ribosomes, tRNA molecules, etc., the
mRNA is translated into individual viral proteins.
4. Replication
As viral protein levels rise, a switch occurs from
translation to replication. Using the negative-sense
genomic RNA as a template, a complementary
+ssRNA is synthesized; this is then used as a
template for the synthesis of new genomic (-)ssRNA,
which is rapidly encapsidated
Replication presumably starts when enough
nucleoprotein is present to encapsidate neo-
synthetized antigenomes and genomes.
5. Budding
The newly formed nucleocapsids and envelope
proteins associate at the host cell’s plasma
membrane; budding occurs, destroying the cell.
These viruses recruit components of the cellular
ESCRT (endosomal sorting complex required for
transport) system to mediate host-assisted viral
budding. SCRT complexes are normally used by the
cell for biological functions involving membrane
remodeling, such as intraluminal vesicle formation,
autophagy or terminal stages of cytokinesis. The
ESCRT family consists of ESCRT-0, ESCRT-I,
ESCRT-II which are primarily involved in cargo
sorting and membrane deformation, and ESCRT-III
which cleaves the bud neck from its cytosolic face . In
the last step, vps4 disassembles the complex. The
budding reaction catalyzed by the ESCRT machinery
has reversed topology when compared with most
other budding processes in the cell, such as
endocytosis and formation of transport vesicles.
6. Release
Finally, the virion is released.