Newsgroup: it.scienza.biologia
Titolo: clonazione: cellule staminali o adulte?

Ho appena sentito alla tv che il Papa è a favore del trapianto di
organi, quale gesto di amore, e all'uso di cellule adulte, se ho capito
bene, x la clonazione, mentre è contrario all'uso di cellule staminali,
sempre x la clonazione.
La mia domanda è questa: che differenza c'è tra le cellule adulte e
quelle staminali? Conosco la differenza "biologica" fra di esse,  ma, da
un punto di vista della clonazione, xché si potrebbe essere favorevoli
all'uso delle prime e
contari all'uso delle staminali??

 sempre x la clonazione.
Mah, veramente io ho capito che è a favore dell'utilizzo di cellule
staminali di adulti e prelevate dal cordone ombelicale. D'altronde,
solo con le cellule staminali si può fare la sperimentazione, se ho
capito bene
Ciao Ciao
AleX

 organi per trapianto, come si sta parlando di fare in questi giorni,
?????? Chi ne sta parlando? A me risulta che si sia parlato di cellule
indifferenziate che, messe nelle opportune condizioni, potrebbero dare
origine a tessuti differenziati di cui si ha bisogno.
Tessuti, non altro, la possibilita' della clonazione di un'intera persona
e' stata esplicitamente esclusa da tutti.
Tra l'altro, non e' necessario che le cellule siano prelevate da un
embrione, ne' sarebbe necessario sopprimere l'embrione in caso si decidesse
di utilizzarlo, ma solo prelevare da esso un certo numero di cellule,
qualcosa che somiglia a una donazione....
Inoltre, c'e' il metodo Dolly :-), che prevede l'uso di un nucleo di una
cellula somatica da inserire in una cellula uovo anucleata (non un
embrione, quindi). Nessuno sta parlando di clonare un'intera persona, anzi
lo si esclude apertamente. Anche perche' fino a prova contraria, anche
senza parlare di anima, una persona non e' solo il prodotto dei suoi geni
ma anche, biologicamente, il frutto delle interazioni tra genotipo e
ambiente, della sua "storia" individuale e in gran parte irripetibile di
relazioni - fisiche e psicologiche- con l'ambiente, i genitori, i parenti,
gli altri.
Sulle stem cells hjo un articolo da Science molto interessante, ve lo
includo e scusate per la tabella che e' venuta male.
STEM CELLS:
Harnessing the Power of Stem Cells
Gretchen Vogel
The isolation of human embryonic stem cells could, in theory, allow
scientists to cultivate any of the body's tissues in the lab, but realizing
this potential won't be easy
When developmental biologist Gary Anderson walks into his lab at the
University of California, Davis, in the morning, he's sometimes greeted by
an amazing sight: a plate of cardiac muscle cells pulsing in rhythm. To
Anderson, though, the sight is frustrating. He'd rather see no change at
all: the same pig embryonic stem (ES) cells he left the night before,
staying immature indefinitely. For reasons Anderson does not yet
understand, however, they spontaneously differentiate into any of a variety
of cell types--sometimes a disorganized blob of nervous tissue or
cartilage, sometimes the heart cells. "We're constantly battling their
desire to differentiate," Anderson says.
That powerful drive to become something else is a signature characteristic
of stem cells, the versatile cells that are one of the hottest and most
controversial topics in developmental biology. The current excitement was
touched off 5 months ago, when two groups reported that they had isolated
the first lines of human ES cells--cells that can not only differentiate
into all types of tissue, but can, under carefully controlled conditions,
be maintained continuously as undifferentiated cells in lab cultures
(Science, 6 November 1998, pp. 1014 and 1145). The work has sparked some
controversy because one group extracted the cells from donated human
embryos from a fertility clinic, while the other used tissue from aborted
fetuses. But it could ultimately open the way to growing replacements for
many types of tissue or even organs damaged by disease (see Perspective on
page 1468).
That's what has made human ES cells such a hot commodity. But they are not
the only kinds of stem cells that researchers have been cultivating. Over
the past few years, scientists have also isolated stem cells from various
tissues in animals and humans, including bone marrow and even brain, that
are not "totipotent"--meaning that they can't form all tissue types, as ES
cells do--but can produce a narrower range of cells, such as the various
blood, muscle, or nerve cells. What's more, recent findings suggest that
these partially differentiated stem cells may be more versatile than
thought.
Whichever kind of stem cell they work with, researchers hoping to channel
them into becoming certain kinds of tissue--say, dopamine-producing neurons
for implantation into patients with Parkinson's disease, heart muscle cells
to repair damaged hearts, or insulin-producing cells for diabetes
patients--will have to solve a great many problems first. Put simply, they
will need to understand and control the process of cell specialization
that, for example, turns stem cells into beating heart cells in Anderson's
lab. "Right now, we can get spontaneous differentiation," says Martin Pera,
a developmental biologist at Monash University, in Melbourne, Australia,
but "we don't understand how to control that process" to produce cells of a
specific lineage.
Human Stem Cells Isolated
Stem cell type              Source              Daughter tissues:
embryonic (ES) - embryo or fetal tissue-    all types
hematopoietic  - adult bone marrow      -blood cells; brain?
neuronal-            fetal brain              neurons; glia; blood?
mesenchymal-  adult bone marrow-     muscle; bone; cartilage;
tendon
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To accomplish their goal of growing replacement tissues in the lab,
researchers will have to identify the signals that tell a stem cell to
become one tissue or another--one of the central mysteries in developmental
biology. "We generally know the vocabulary" of growth factors and other
molecules that help determine cell fates, says stem cell researcher Roger
Pedersen of the University of California, San Francisco. "At least we know
what to listen for." But development also requires direct communication
between cells and their neighbors, and Pedersen adds, "Eavesdropping on the
particular conversation going on between the small group of founder cells
in the embryo and their environment is not easy." Once the conversation is
known, researchers will have to take the next step: determining whether
they can reproduce those signals for cells growing in lab cultures.
Blood and brains and bone
The challenges are large, but already researchers have some promising
clues. Much of the success so far has come in directing the differentiation
of the tissue-specific cells. For example, a decade after scientists first
isolated the stem cells that form blood cells from mouse bone marrow,
researchers have learned how to identify and select such hematopoietic stem
cells from human bone marrow, support them as they develop into blood
precursor cells, and then use an array of growth factors and other
regulatory proteins to guide their development into red cells and other
mature blood cells.
Scientists also have promising clues about how to guide the development of
neuronal stem cells. Developmental neurobiologist David Anderson of the
California Institute of Technology (Caltech) in Pasadena and his
colleagues, working on cells derived from fetal rats, have shown that
several proteins, including neuregulin and bone morphogenic protein 2
(BMP2), can nudge neural stem cells toward becoming neurons, the neuronal
support cells known as glia, or even smooth muscle. The researchers don't
yet know exactly how the molecules are working, however.
And it takes more than just the right molecules to get stem cells to
differentiate. For example, researchers have found that even with the best
neuronal growth factors known, they could at most get only about half of
the neural stem cells in their cultures to become neurons. Developmental
neurobiologists think that may be because a developing brain cell relies on
a specific combination of signals from its neighbors, reflecting its
three-dimensional position in relation to other developing brain cells, to
determine the specific type of cell it becomes.
"Essentially, to induce that differentiation [into neurons], you need the
other cell types present," says developmental geneticist Robin Lovell-Badge
of the National Institute for Medical Research in London, who is among
those working on the problem. "It's never going to be a simple story."
Caltech's Anderson agrees: "We are far from being able to take a cell from
the brain and differentiate it, at will, into a desired cell type."
Even mechanical forces can affect stem cell development. Cell biologist
Daniel Marshak and his colleagues at Osiris, a biotechnology company in
Baltimore, have been working on mesenchymal stem cells, which produce bone,
cartilage, fat, and muscle. They and others have found that compressing the
cells encourages bone development, while a tensile force--essentially
stretching the matrix surrounding the cells--encourages development of
tendons. Cartilage, on the other hand, will only form if the cells are
clumped together or grown on a three-dimensional support, says Marshak.
Although scientists are not as adept at controlling the more primitive ES
cells, they have made some progress there, too. Because human ES cells have
been available only for a few months, most of this work has been done on
mouse ES cells and cell lines from teratocarcinomas. These testicular or
ovarian tumors grow from undifferentiated cells that have properties
similar to those of ES cells. The tumors are masses of varied tissues,
sometimes sprouting hair and even teeth, and although the cells are good
for study, they aren't as promising for human therapies as ES cells are
because of their tumor-forming potential.
So far, researchers have found that they can induce ES and teratocarcinoma
cells to produce both neuronal and mesenchymal cells. In fact, some hints
from developmental biologists suggest that neuronal cells may be a
"default" fate for undifferentiated cells--meaning that's what they form
when left to their own devices. Perhaps because of that, it is relatively
easy to turn ES cells into neurons. Adding retinoic acid--which helps drive
nervous-system development in the embryo--at the proper time "will make 90%
of the cells go down the neural lineage path," says David Gottlieb of
Washington University in St. Louis. Those cells, in turn, differentiate
spontaneously into neurons and glia.
Producing mesenchymal cells from ES or teratocarcinoma cells requires a
different signal: BMP4. With the right factors, Gottlieb says, "you can
tilt their fate in the desired direction." No one is yet sure, however,
which factors to use to encourage the formation of the third major type of
tissue, endoderm, which gives rise to the gut, lungs, and inner organs. But
developmental biologist Douglas Melton at Harvard University has been able
to select a few mouse ES cells that differentiate spontaneously into
endoderm cells.
He can also persuade those endodermal cells to become pancreatic cell
precursors--just a few steps away from the insulin-producing cells needed
by diabetes patients--by exposing them to cells from the "pancreatic bud"
dissected from another mouse. Those cells "send out signals saying, 'Come
join us and become pancreas,' " Melton says. Of course, to make human
pancreatic cells, scientists would have to reproduce those signals without
the help of already-developing tissue, since work with fetal tissue raises
serious ethical, moral, and perhaps legal issues, Melton notes.
Unexpected versatility
But ES cells may not be the only hope for cultivating a wide range of
tissues. There are signs that the more differentiated kinds of stem cells
might have greater potential for tissue replacement than researchers had
assumed. In a major surprise that seems to have overturned some
long-standing beliefs about developmental biology, scientists reported
earlier this year that neural stem cells from the mouse brain, when
transplanted into mice whose bone marrow has been largely destroyed,
develop into blood cells (Science, 22 January, pp. 471 and 534).
Although amphibians and other "lower organisms" can reprogram their cells
to regrow body parts--new tails, for example, and even new
limbs--developmental biologists have long assumed that mammalian cells are
not so versatile. The standard view held that once a more specialized cell
forms, its fate can't be altered so that it becomes something else. But
"there is very little data to support [that assumption]," says
developmental neurobiologist Ron McKay of the National Institute of
Neurological Disorders and Stroke. The new observations suggest "that cells
can make unexpected jumps between fates," he says. "It's going to be
interesting to see where those jumps can occur."
Neuronal stem cells may not be the only ones able to switch fates. Last
year, for example, developmental biologist Darwin Prockop of the Allegheny
University of the Health Sciences in Philadelphia and his colleagues
reported in the Proceedings of the National Academy of Sciences that when
bone marrow stromal cells that would normally form muscle and other
mesenchymal tissues are injected into the brains of mice, the cells become
glia. And Juan Sanchez-Ramos of the University of South Florida in Tampa
and his colleagues have preliminary evidence, presented at a meeting last
year, that exposure to neural growth factors in culture can also send
marrow cells down the road to becoming neurons.
Many stem cell researchers are greeting the neuronal stem cell-to-blood
cell results with caution, however. "It's a preliminary analysis," says
developmental hematologist Leonard Zon of Children's Hospital in Boston.
The blood cells may have grown not from neuronal stem cells, he says, but
from a more primitive stem cell also in the sample.
But if the results are confirmed, the stem cell versatility could open the
way to cell therapies that don't rely on embryonic stem cells, with their
ethical and legal entanglements. A sample of a patient's own bone-marrow
cells, drawn through a needle inserted into the hip bone, could be
manipulated in culture and perhaps used to replace neurons in the brain or
damaged heart muscle.
Such applications, however, face the same hurdles as other potential stem
cell treatments. More immediately exciting, say many scientists in this
area, is the chance to study what it is about a cell that allows it to
remain malleable and able to change its fate in response to environmental
cues.
Indeed, the efforts to harness stem cells' potential for biomedical
applications is a boon for cell and developmental biologists. With cultured
stem cells, cellular changes "that have only occurred in the complex
context of the early embryo are now happening before your eyes in a dish,"
says Washington University's Gottlieb. And those changes seem to be very
similar to the ones that happen in the developing embryo, producing
normal-looking neurons that make synapses and heart cells that set up
rhythms. "What we're looking forward to is a much greater level of
understanding and control," he says. "It's a field in which chapter one has
been written. I'm looking forward to chapter two."

 e' stata esplicitamente esclusa da tutti
Cio' detto, e scusandomi per la lunghesza del post precedente, penso sia il
caso di dire che e' opportuno che la scienza si ponga dei limiti. Ci sono
dei valori che, anche per la coscienza di un laico, vanno rispettati.
Nessuno, credo, ucciderebbe a sangue freddo un suo simile per sperimentare
un farmaco.
Il problema e' farlo sapendo esattamente di che cosa si sta parlando. Cio'
non vuol dire che ne debbano parlare solo gli scienziati (nessuna
corporazione ha il diritto di decidere per tutti, sia che porti la tonaca
che il camice), ma che e' necessario dotare tutti i cittadini di strumenti
culturali adeguati a cio' che la societa' di oggi sta proponendo a
velocita' accelerata. Un po' meno di latino e un po' piu' di cultura
scientifica nei programmi scolastici, un po' piu' di umilta' da parte di
tutti, ma soprattutto di politici e media, nell'ammettere, quando e' il
caso, la propria impreparazione.

1- I cattolici, credendo nella sacralità della vita e nel fatto che una cell
fecondata è a tutti gli effetti una vita umana, rifiutano ogni manipolazione
sugli embrioni, e fin qua ci era tutto chiaro
2- La clonazione è una cosa diversa da quello che si sta facendo, o meglio,.
è assai simile ma lo scopo è ottenere tessuti e non organismi. In questo
senso la chiesa è contro la clonazione in ogni senso ma non contro
l'impianto di un nucleo somatico in una cell staminale (non embrionale) allo
scopo di differenziare unico tessuto e/o organo per utilizzarlo nei
trapianti.
Piuttosto la domanda che mi pongo io è:
La chiesa è d'accordo con gli xenotrapianti, ma come la mettiamo con la
umanizzazione degli animali (come il maiale) allo scopo di avere organi
compatibili?

 maniera industriale!
Le cose sono andate avanti da allora. 
-----------------------------------------------------------------------------
   Title                                                                       
    Mice cloned from embryonic stem cells.                                     
   Source                                                                      
    Proceedings of the National Academy of Sciences of the United States of  
    America.  96(26):14984-9, 1999 Dec 21.                                     
   Abbreviated Source                                                          
    Proc Natl Acad Sci U S A.  96(26):14984-9, 1999 Dec 21.                    
   Abstract                                                                    
    Cloning allows the asexual reproduction of selected individuals such that  
    the offspring have an essentially identical nuclear genome. Cloning by     
    nuclear transfer thus far has been reported only with freshly isolated     
    cells and cells from primary cultures. We previously reported a method of  
    cloning mice from adult somatic cells after nuclear transfer by            
    microinjection. Here, we apply this method to clone mice from widely    
    available, established embryonic stem (ES) cell lines at late passage.     
    With the ES cell line R1, 29% of reconstructed oocytes developed in vitro  
    to the morula/blastocyst stage, and 8% of these embryos developed to       
    live-born pups when transferred to surrogate mothers. We thus cloned 26    
    mice from R1 cells. Nuclei from the ES cell line E14 also were shown to    
    direct development to term. We present evidence that the nuclei of ES      
    cells at G(1)- or G(2)/M-phases are efficiently able to support full       
    development. Our findings demonstrate that late-passage ES cells can be    
    used to produce viable cloned mice and provide a link between the          
    technologies of ES cells and animal cloning. It thus may be possible to    
    clone from a single cell a large number of individuals over an extended    
    period.                                                                    
----------------------------------------------------------------------------
In pratica gli autori hanno fatto questo:
Nucleo cellula somatica----> trapianto oocita-----> Blastocisti
                                                            |
                                                            |
Secondo trapianto di nuclei <------ Cultura ES cells< ------+
|
|
+--------> Clonaggio individuo
Considerando poi che una cultura di ES cell  e` una fonte inesauribile
di nuclei, poco  importa che solo  (si fa per dire)  meno del 3% degli
oociti  trapiantati arriva al   termine della gestazione. Ovviamente i
numeri sono destinati comunque a salire.
-- 
ciao | it.* non piu` l'unica gerarchia italiana (
http://go.to/Mamo_faq
)
cf   |  - italia.*   gruppi creati e gestiti dalle reti civiche locali
-----+  - i2000.*    gestita dalla FOR e autenticata in scrittura
        - free.it.*  su Libero e Tiscali, anarchica e con seri problemi

 ma anche, biologicamente, il frut to delle interazioni tra genotipo e


Ciao! Il giorno Wed, 30 Aug 2000 02:08:07 +0200, non sapendo che fare,
SEAWOLF ha scritto ben 295 righe, tra cui:
BEN 252 di QUOTE !!!!!!!!!!!!!
Eddai lupo di mare, questa non me la dovevi proprio fare !!!!!!!!!!!!
AleX

 compatibili?
Mi preoccuperei di piu' della possibilita' che siano trasmessi all'uomo
retrovirus di origine animale.
Mi pare che ne siano stati individuati anche di recente. Quanto alla
posizione della chiesa, per tagliare la testa al toro suggerirei l'uso di
cellule staminali diverse da quelle embrionali.
Non mi pare il caso di procedere a carro armato, senza tenere conto delle
particolari sensibilita' e di posizioni diverse; anche perche', a mio
modesto avviso, l'integralismo scientista non e' migliore di ogni altro
integralismo. L'introduzione di nuove tecnologie produce sempre un impatto
sulla societa' di cui e' opportuno tenere conto, come sarebbe opportuno
porsi, di quando in quando, qualche domanda sulle implicazioni non solo
filosofiche o morali, ma anche relative alle possibili conseguenze
sull'ambiente (vedi caso ogm). Domande, dico, non necessariamente
preclusioni.
Il pericolo piu' grosso, fiutando l'aria, mi pare in ogni caso un altro:
troppo spesso la ricerca "pura", che dovrebbe produrre conoscenza, si piega
alle ragioni di mercato, e si interessa non solo degli aspetti teorici
quanto direttamente dell'introduzione di nuove tecnologie, confondendo
quindi due campi, due piani, che, per il bene di tutti, dovrebbero restare
il pčiu' possibile differenziati.
So bene che le ricerche hanno bisogno di finanziamenti, ma non e' una
posizione debole quella del ricercatore che accetta di sottomettersi alla
logica economica, ti finanzio se sei in grado di farmi guadagnare, e nel
minor tempo possibile? Non sarebbe il caso di rivendicare l'importanza, e
anche la produttivita', ma senza il vincolo del ritorno immediato in
termini di profitto, dello sviluppo delle conoscenze, e il diritto degli
scienziati di ricevere finanziamenti in quanto produttori di sapere, non
solo di tecniche e prodotti immediatamente utilizzabili?
Anni fa un editoriale de Le Scienze lamentava che la ricerca biologica, da
tempo, non producesse piu' significativi avanzamenti concettuali, nel senso
di scoperte che portassero al chiarimento ulteriore dei meccanismi alla
base della vita, ma solo nuove tecniche. Sia chiaro, anche tecniche
d'indagine che avrebbero avuto, naturalmente, grande importanza anche sul
piano della conoscenza; ma niente di paragonabile alla scoperta della
doppia elica o all'interpretazione del codice genetico. Oggi la situazione
e' certamente diversa, nuove scoperte teoriche ci sono state, ma quasi come
effetto collaterale dello sviluppo delle tecnologie, che rappresenta
tuttora il filone piu' importante, e ovviamente redditizio. La ricerca
attuale mi sembra ancora in gran parte impaniata in questa confusione di
ruoli e prospettive. Vedi il dibattito sul brevetto dei geni.

 ha scritto nel messaggio
news:wFSsOWjYOyonnD...@4ax.com...

SCUSAAAAAAAA!!!!!
Ieri mi faceva fatica, perdonatemi!:)))
Ciao,
Seawolf.

 Seawolf.
Ciao Ciao
AleX

L'articolo che ho postato sulle stem cells (Harnessing the power of stem
cells, Vogel e al) e' stato pubblicato su Science, Volume 283, Number 5407
Issue of 5 Mar 1999, pp. 1432 - 1434
Altri articoli nello stesso numero:
A Man in a Hurry. Joseph Alper
Science 1999 283: 1434-1435. (in News Focus)
 Putting Stem Cells to Work. Davor Solter and John Gearhart
Science 1999 283: 1468-1470.