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Tuesday, May 9, 2023

05-09-2023-1755 - immortalised cell line

An immortalised cell line is a population of cells from a multicellular organism which would normally not proliferate indefinitely but, due to mutation, have evaded normal cellular senescence and instead can keep undergoing division. The cells can therefore be grown for prolonged periods in vitro. The mutations required for immortality can occur naturally or be intentionally induced for experimental purposes. Immortal cell lines are a very important tool for research into the biochemistry and cell biology of multicellular organisms. Immortalised cell lines have also found uses in biotechnology.

An immortalised cell line should not be confused with stem cells, which can also divide indefinitely, but form a normal part of the development of a multicellular organism. 

Relation to natural biology and pathology

There are various immortal cell lines. Some of them are normal cell lines (e.g. derived from stem cells). Other immortalised cell lines are the in vitro equivalent of cancerous cells. Cancer occurs when a somatic cell which normally cannot divide undergoes mutations which cause de-regulation of the normal cell cycle controls leading to uncontrolled proliferation. Immortalised cell lines have undergone similar mutations allowing a cell type which would normally not be able to divide to be proliferated in vitro. The origins of some immortal cell lines, for example HeLa human cells, are from naturally occurring cancers. HeLa, the first immortal human cell line on record to be successfully isolated and proliferated by a laboratory, was taken from Henrietta Lacks (without informed consent[1]) in 1951 at Johns Hopkins Hospital in Baltimore, Maryland.

Role and uses

Immortalised cell lines are widely used as a simple model for more complex biological systems, for example for the analysis of the biochemistry and cell biology of mammalian (including human) cells.[2] The main advantage of using an immortal cell line for research is its immortality; the cells can be grown indefinitely in culture. This simplifies analysis of the biology of cells which may otherwise have a limited lifetime.

Immortalised cell lines can also be cloned giving rise to a clonal population which can, in turn, be propagated indefinitely. This allows an analysis to be repeated many times on genetically identical cells, which is desirable for repeatable scientific experiments. The alternative, performing an analysis on primary cells from multiple tissue donors, does not have this advantage.

Immortalised cell lines find use in biotechnology, where they are a cost-effective way of growing cells similar to those found in a multicellular organism in vitro. The cells are used for a wide variety of purposes, from testing toxicity of compounds or drugs to production of eukaryotic proteins. 

Limitations

Changes from nonimmortal origins

While immortalised cell lines often originate from a well-known tissue type, they have undergone significant mutations to become immortal. This can alter the biology of the cell and must be taken into consideration in any analysis. Further, cell lines can change genetically over multiple passages, leading to phenotypic differences among isolates and potentially different experimental results depending on when and with what strain isolate an experiment is conducted.[3]

Contamination with other cells

Main article: List of contaminated cell lines

Many cell lines that are widely used for biomedical research have been contaminated and overgrown by other, more aggressive cells. For example, supposed thyroid lines were actually melanoma cells, supposed prostate tissue was actually bladder cancer, and supposed normal uterine cultures were actually breast cancer.[4]

 

Methods of generation

There are several methods for generating immortalised cell lines:[5]

  1. Isolation from a naturally occurring cancer. This is the original method for generating an immortalised cell line. Major examples include human HeLa, the line is derived from cervical cancer cells taken on February 8, 1951 from Henrietta Lacks, a 31-year-old African-American mother of five, who died of cancer on October 4, 1951.[6]
  2. Introduction of a viral gene that partially deregulates the cell cycle (e.g., the adenovirus type 5 E1 gene was used to immortalise the HEK 293 cell line; the Epstein–Barr virus can immortalise B lymphocytes by infection[7]).
  3. Artificial expression of key proteins required for immortality, for example telomerase which prevents degradation of chromosome ends during DNA replication in eukaryotes. [8]
  4. Hybridoma technology, specifically used for generating immortalised antibody-producing B cell lines, where an antibody-producing B cell is fused with a myeloma (B cell cancer) cell.[9

 

Examples

There are several examples of immortalised cell lines, each with different properties. Most immortalised cell lines are classified by the cell type they originated from or are most similar to biologically.

 

 

https://en.wikipedia.org/wiki/Immortalised_cell_line

 

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05-09-2023-1553 - presynaptic neuron reference (synapse, Monoamine releasing agent, nitrous oxide, etc.)

 

In the nervous system, a synapse[1] is a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or to the target effector cell.

Synapses are essential to the transmission of nervous impulses from one neuron to another. Neurons are specialized to pass signals to individual target cells, and synapses are the means by which they do so. At a synapse, the plasma membrane of the signal-passing neuron (the presynaptic neuron) comes into close apposition with the membrane of the target (postsynaptic) cell. Both the presynaptic and postsynaptic sites contain extensive arrays of molecular machinery that link the two membranes together and carry out the signaling process. In many synapses, the presynaptic part is located on an axon and the postsynaptic part is located on a dendrite or soma. Astrocytes also exchange information with the synaptic neurons, responding to synaptic activity and, in turn, regulating neurotransmission.[2] Synapses (at least chemical synapses) are stabilized in position by synaptic adhesion molecules (SAMs) projecting from both the pre- and post-synaptic neuron and sticking together where they overlap; SAMs may also assist in the generation and functioning of synapses.[3] 

https://en.wikipedia.org/wiki/Synapse

monoamine releaser, is a drug that induces the release of a monoamine neurotransmitter from the presynaptic neuron into the synapse, leading to an increase in the extracellular concentrations of the neurotransmitter.  

https://en.wikipedia.org/wiki/Monoamine_releasing_agent

https://en.wikipedia.org/wiki/Monoamine_releasing_agent

https://en.wikipedia.org/wiki/Membrane_transport_protein

https://en.wikipedia.org/wiki/Reverse_transport

https://en.wikipedia.org/wiki/Vesicular_monoamine_transporter_2

https://en.wikipedia.org/wiki/2C-E

https://en.wikipedia.org/wiki/Benzylpiperazine

https://en.wikipedia.org/wiki/Norpropylhexedrine

https://en.wikipedia.org/wiki/Cathine

https://en.wikipedia.org/wiki/Serotonin

https://en.wikipedia.org/wiki/Tyramine

https://en.wikipedia.org/wiki/Propylhexedrine

https://en.wikipedia.org/wiki/Nitrous_oxide

https://en.wikipedia.org/wiki/Nitric_oxide

https://en.wikipedia.org/wiki/Purging_(gas)

https://en.wikipedia.org/wiki/Pyrophoricity

https://en.wikipedia.org/wiki/Argon

https://en.wikipedia.org/wiki/Hexane

https://en.wikipedia.org/wiki/Maleic_anhydride

https://en.wikipedia.org/wiki/Dehydrogenation

https://en.wikipedia.org/wiki/Slag

https://en.wikipedia.org/wiki/Ferroalloy

https://en.wikipedia.org/wiki/Electric_arc_furnace

https://en.wikipedia.org/wiki/Steelmaking

https://en.wikipedia.org/wiki/Foundry

Hydrogen gas is a reducing agent when it reacts with non-metals and an oxidizing agent when it reacts with metals.  

https://en.wikipedia.org/wiki/Reducing_agent

An anode is an electrode of a polarized electrical device through which conventional current enters the device. This contrasts with a cathode, an electrode of the device through which conventional current leaves the device. A common mnemonic is ACID, for "anode current into device".[1] The direction of conventional current (the flow of positive charges) in a circuit is opposite to the direction of electron flow, so (negatively charged) electrons flow out the anode of a galvanic cell, into an outside or external circuit connected to the cell. For example, the end of a household battery marked with a "-" (minus) is the anode.

In both a galvanic cell and an electrolytic cell, the anode is the electrode at which the oxidation reaction occurs. In a galvanic cell the anode is the wire or plate having excess negative charge as a result of the oxidation reaction. In an electrolytic cell, the anode is the wire or plate upon which excess positive charge is imposed.[2] As a result of this, anions will tend to move towards the anode where they will undergo oxidation.

Historically, the anode of a galvanic cell was also known as the zincode because it was usually composed of zinc.[3][4]: pg. 209, 214  

https://en.wikipedia.org/wiki/Anode

Hydrogen (whose reduction potential is 0.0) acts as an oxidizing agent because it accepts an electron donation from the reducing agent lithium (whose reduction potential is -3.04), which causes Li to be oxidized and hydrogen to be reduced.

H2(g) + F2(g) → 2 HF(g)[b]

Hydrogen acts as a reducing agent because it donates its electrons to fluorine, which allows fluorine to be reduced. 

https://en.wikipedia.org/wiki/Reducing_agent

 

The Great Oxidation Event (GOE), also called the Great Oxygenation Event, the Oxygen Catastrophe, the Oxygen Revolution, the Oxygen Crisis, or the Oxygen Holocaust,[2] was a time interval during the Paleoproterozoic era when the Earth's atmosphere and the shallow ocean first experienced a rise in the amount of oxygen.[3] This began approximately 2.460–2.426 Ga (billion years) ago, during the Siderian period, and ended approximately 2.060 Ga, during the Rhyacian.[4] Geological, isotopic, and chemical evidence suggests that biologically-produced molecular oxygen (dioxygen, O2) started to accumulate in Earth's atmosphere and changed it from a weakly reducing atmosphere practically free of oxygen into an oxidizing atmosphere containing abundant oxygen,[5] with oxygen levels being as high as 10% of their present atmospheric level by the end of the GOE.[6]

The sudden injection of toxic oxygen into an anaerobic biosphere may have caused the extinction of many existing anaerobic species on Earth. Although the event is inferred to have constituted a mass extinction,[7] due in part to the great difficulty in surveying microscopic species' abundances, and in part to the extreme age of fossil remains from that time, the Great Oxidation Event is typically not counted among conventional lists of "great extinctions", which are implicitly limited to the Phanerozoic eon. In any case, isotope geochemical data from sulfate minerals have been interpreted to indicate a decrease in the size of the biosphere of >80% associated with changes in nutrient supplies at the end of the GOE.[8]

The GOE is inferred to have been caused by cyanobacteria producing the oxygen, which may have enabled the subsequent development of multicellular life-forms like the Francevillian biota.[9] 

https://en.wikipedia.org/wiki/Great_Oxidation_Event

Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as 101,325 Pa (1,013.25 hPa), which is equivalent to 1013.25 millibars,[1] 760 mm Hg, 29.9212 inches Hg, or 14.696 psi.[2] The atm unit is roughly equivalent to the mean sea-level atmospheric pressure on Earth; that is, the Earth's atmospheric pressure at sea level is approximately 1 atm.

In most circumstances, atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point. As elevation increases, there is less overlying atmospheric mass, so atmospheric pressure decreases with increasing elevation. Because the atmosphere is thin relative to the Earth's radius—especially the dense atmospheric layer at low altitudes—the Earth's gravitational acceleration as a function of altitude can be approximated as constant and contributes little to this fall-off. Pressure measures force per unit area, with SI units of pascals (1 pascal = 1 newton per square metre, 1 N/m2). On average, a column of air with a cross-sectional area of 1 square centimetre (cm2), measured from the mean (average) sea level to the top of Earth's atmosphere, has a mass of about 1.03 kilogram and exerts a force or "weight" of about 10.1 newtons, resulting in a pressure of 10.1 N/cm2 or 101 kN/m2 (101 kilopascals, kPa). A column of air with a cross-sectional area of 1 in2 would have a weight of about 14.7 lbf, resulting in a pressure of 14.7 lbf/in2. 

https://en.wikipedia.org/wiki/Atmospheric_pressure

https://en.wikipedia.org/wiki/Cyanobacteria

https://en.wikipedia.org/wiki/Carbon_monoxide

 https://en.wikipedia.org/wiki/Banded_iron_formation

https://en.wikipedia.org/wiki/Lithium_aluminium_hydride


 

 

A substance is pyrophoric (from Greek: πυροφόρος, pyrophoros, 'fire-bearing') if it ignites spontaneously in air at or below 54 °C (129 °F) (for gases) or within 5 minutes after coming into contact with air (for liquids and solids).[1] Examples are organolithium compounds and triethylborane. Pyrophoric materials are often water-reactive as well and will ignite when they contact water or humid air. They can be handled safely in atmospheres of argon or (with a few exceptions) nitrogen. Class D fire extinguishers are designated for use in fires involving pyrophoric materials. A related concept is hypergolicity, in which two compounds spontaneously ignite when mixed. 

https://en.wikipedia.org/wiki/Pyrophoricity

https://en.wikipedia.org/wiki/Triethylborane

 https://en.wikipedia.org/wiki/Tetrahydrofuran

https://en.wikipedia.org/wiki/Coking

https://en.wikipedia.org/wiki/Dentistry

https://en.wikipedia.org/wiki/Induction_furnace

https://en.wikipedia.org/wiki/Dust

https://en.wikipedia.org/wiki/Blast_furnace

https://en.wikipedia.org/wiki/Smelting

https://en.wikipedia.org/wiki/Reducing_agent


The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth creates pressure, absorbs most meteoroids and ultraviolet solar radiation, warms the surface through heat retention (greenhouse effect), allowing life and liquid water to exist on the Earth's surface, and reduces temperature extremes between day and night (the diurnal temperature variation). 

https://en.wikipedia.org/wiki/Atmosphere_of_Earth

 

https://en.wikipedia.org/wiki/Reducing_agent

 

Sodium amalgam, commonly denoted Na(Hg), is an alloy of mercury and sodium. The term amalgam is used for alloys, intermetallic compounds, and solutions (both solid solutions and liquid solutions) involving mercury as a major component. Sodium amalgams are often used in reactions as strong reducing agents with better handling properties compared to solid sodium. They are less dangerously reactive toward water and in fact are often used as an aqueous suspension.

Sodium amalgam was used as a reagent as early as 1862.[1] A synthesis method was described by J. Alfred Wanklyn in 1866.[2]

Structure and compositions

No particular formula is assigned to "sodium amalgam". Na5Hg8 and Na3Hg are well defined compounds. In sodium amalgams, the Hg-Hg distances are expanded to around 5 Å vs. about 3 Å for mercury itself.[3] Usually amalgams are classified on the weight percent of sodium. Amalgams with 2% Na are solids at room temperature, whereas some more dilute amalgams remain liquid.[4]

Preparation

External video
Demonstration and commentary on the preparation of sodium amalgam
YouTube logo
via YouTube
video icon Mixing sodium with mercury (31 December 2018), by NileRed

Metallic sodium dissolves in mercury exothermically, i.e. with the release of heat, therefore, formation of sodium amalgam is famously dangerous for generating sparks.[5] The process causes localised boiling of the mercury and for this reason the formation is usually conducted in a fume hood and often performed using air-free techniques, such as synthesis under anhydrous liquid paraffin. Sodium amalgam may be prepared in the laboratory by dissolving sodium metal in mercury or the reverse.[6][7][8] Sodium amalgams can be purchased from chemical supply houses.

Uses

Sodium amalgam has been used in organic chemistry as a powerful reducing agent, which is safer to handle than sodium itself. It is used in Emde degradation, and also for reduction of aromatic ketones to hydrols.[9]

A sodium amalgam is used in the design of the high pressure sodium lamp providing sodium to produce the proper color, and mercury to tailor the electrical characteristics of the lamp.

Mercury cell electrolysis

Sodium amalgam is a by-product of chlorine made by mercury cell electrolysis. In this cell, brine (concentrated sodium chloride solution) is electrolysed between a liquid mercury cathode and a titanium or graphite anode. Chlorine is formed at the anode, while sodium formed at the cathode dissolves into the mercury, making sodium amalgam. Normally this sodium amalgam is drawn off and reacted with water in a "decomposer cell" to produce hydrogen gas, concentrated sodium hydroxide solution, and mercury to be recycled through the process. In principle, all the mercury should be completely recycled, but inevitably a small portion goes missing. Because of concerns about this mercury escaping into the environment, the mercury cell process is generally being replaced by plants which use a less toxic cathode.

References

  • Atkinson, E. (1862). "XLI. Chemical notices from foreign journals". The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science. 24 (161): 305–311. doi:10.1080/14786446208643359.

  • Wanklyn, J. Alfred (1866). "XII.—On a new method of forming organo-metallic bodies". J. Chem. Soc. 19: 128–130. doi:10.1039/JS8661900128.

  • Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.

  • Keith R. Buszek "Sodium Amalgam" in Encyclopedia of Reagents for Organic Synthesis, 2001, John Wiley. doi:10.1002/047084289X.rs040

  • W.4r B. Renfrow Jr and C. R. Hauser (1993). "Sodium triphenylmethyl". Organic Syntheses.; Collective Volume, vol. 2, p. 607

  • 3% Na in Hg: Babcock, S. H.; Lankelma, H. P.; Vopicka, E. (1939). Sodium Amalgam. Inorg. Synth. Inorganic Syntheses. Vol. 1. p. 10. doi:10.1002/9780470132326.ch4. ISBN 978-0-470-13232-6.

  • see the notes in Richard N. McDonald and Charles E. Reineke (1988). "trans-3,5-Cyclohexadiene-1,2-dicarboxylic acid". Organic Syntheses.; Collective Volume, vol. 6, p. 461

  • Procedure for making Na(Hg) by addition of Na to Hg: Tony C. T. Chang, Myron Rosenblum, and Nancy Simms (1993). "Vinylation of Enolates with a Vinyl Cation Equivalent". Organic Syntheses.; Collective Volume, vol. 8, p. 479

    1. Bachmann, W. E. (February 1933). "The Mechanism of Reduction by Sodium Amalgam and Alcohol. I. The Reduction of Aromatic Ketones to Hydrols". Journal of the American Chemical Society. 55 (2): 770–774. doi:10.1021/ja01329a051. ISSN 0002-7863.

    External links

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