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18

I'd like to know what is the reference for amoebic learning. I cannot comment directly on this, but there is some evidence for "adaptive anticipation" in both prokaryotes and single-celled Eukaryotes which do not have a nervous system. In the case of E. coli, it has been shown that the bacteria can anticipate the environment it is about to enter. E. coli ...


13

Generally, cold suppresses sweetness. As an example, consider soft drinks that are usually served cold: they taste sweeter when warm (like you said with your examples of drinks). Our taste receptors send a stronger signal to the brain when activated by warmer substances and so the perception of sweetness, in this case, is lessened when we consume cold food ...


8

In addition to the excellent response up top (by Poshpaws), one can also imagine how these systems work by looking at recent synthetic examples of single-celled organism memory. It is possible to design various bistable switches using protein pathways, RNAi, or other means that will latch a particular state. In that way, an organism could effectively "...


8

After we have eaten... the maximum blood supply is transferred towards the digestive system so that digestion is done, and therefore the brain to does not get adequate blood supply. Am I right about this? This is a very, very common myth, but it is a myth. Because blood flow and oxygen delivery to the brain is critical for survival, cerebral circulation is ...


7

The CD4 receptor is vital for the proper functioning of the immune system. It is found not only on T-Lymphocytes, but also on macrophages and dendritic cells. Its function on T-cells is to stabilize the interaction between the T-Cell receptor and the MHC Class 2 (often known as HLA II in humans) antigen complex on antigen presenting cells and improves the ...


6

A mechanical stimulus can act on a tissue with elastic and viscoelastic properties in two ways [1, 2]: distort the cellular membrane which leads to opening of ion channels. create tension on the extracellular matrix or cytoskeleton, to which a ion channel is bound, thus leading to opening of the channel. Stretch-activated ion channels opening leads to the ...


6

Short answer Temperature differences of 0.02 degrees Celcius can be distinguished, dependent on various factors including experimental conditions and bodily location. Background The ability to discriminate temperature differences depends on whether it is a cooling or heating pulse, the skin temperature, the duration of the temperature stimulus, age, bodily ...


5

The definition of "ligand" in the question, "a molecule or ion which donates a pair of electrons to a central transition metal ion in a complex" is clearly a more technical 'chemistry-type' of definition. Ligands in biology and medicine can be all sorts of molecules, though most of the time we think of them as molecules that bind to a particular receptor. ...


5

This isn't a case of gene splicing causing different protein variants. In the studies that identified these two functions (GHB sensitivity and riboflavin transport), they were using DNA derived from mRNA (cDNA), which means what was being expressed in their experiments did not have introns, so there was no chance for alternative splicing. This gene has a ...


5

Photoreceptors themselves dont act as oscilators, a single receptor is either 'on' or 'off' - it does not respond differently to different wavelenghts. Humans have Trichromatic vision, which means that we have 3 different kinds of photo-receptors that respond differently to light of a given wavelength at a given intensity. By combining multiple signals from ...


5

Specific parts — moieties — of an agonist molecule bind to the receptor protein, causing the receptor to change shape, which in turn initiates a signaling pathway inside the cell. Some agonists are better at causing the receptor to change to its "optimal shape" for relaying signal. These are called "full agonists". Other agonists cause a partial change in ...


4

An antagonist is a substance that blocks a particular pathway (a receptor). You can therefore test whether a particular drug acts through the opioid system by using an opioid antagonist. If your substance still works despite the presence of the antagonist (which should block the opoiod receptors), you can conclude that it is not working thorough the opioid ...


4

Short answer No, orally taken painkillers act systemically. Background Taking a painkiller orally results in the drug being taken up into the bloodstream by the digestive system. From there it can potentially reach all tissues. In other words, a pain response does not act as a chaperone. A hypothetical drug that would home in on tissues with a pain ...


4

As far as I know there are 5 receptors for far-red and red light which are the phytochroms(phyA-phyE) Its all about the ratio between red and far-red light. Each phytochrom has an inactive(PR) and an active(PFr) conformation. phyA is the only phytochrom which is activated by far-red light, so its active state is PR. (Only if the ratio between red and far-...


4

That paper is describing the binding between the 5HT3 receptor and some high-affinity ligand, not serotonin. Numbers of serotonin probably vary according to the precise receptor (species, subunits, etc), but for a ballpark figure this source says 1.7/s, giving half time of ~400 ms. That estimate is based on solution changes, so I'd say it's an upper bound. ...


4

Both internalization (sometimes with degradation) and changes in gene expression can occur; the circumstances leading to the down regulation determine which (or both). It isn't necessary for receptors to be bound to their ligand to be internalized, though, and it isn't the internalization of receptors that causes changes in gene expression (I suppose it is ...


4

Yes. Trypsin cleaves proteins and can do so quite indiscriminately if left on for very long. Trypsin is primarily used to cleave the proteins that cells use to adhere to each other and the plate in culture. It can cleave other membrane bound proteins as well, including receptors. https://jbiomedsci.biomedcentral.com/articles/10.1186/1423-0127-17-36


4

Large proteins are challenging for NMR: the more amino acids, the more peaks one has to assign. Peak overlap is also more likely the more amino acids you have, making assignment difficult. Some NMR strategies work well for studying dynamics of large proteins, but as far as structure determination is concerned, there definitely is a critical size past which ...


3

The "crash" effect is typically perceived as a deterioration in affect. With drugs, this deterioration happens as the drug is cleared from blood circulation, particularly cerebral circulation. With the ingestion of amphetamines, there is a brief reuptake of certain neurotransmitters, particularly dopamine and norepinephrine. Amphetamines also temporarily ...


3

Short answer Slowly adapting mechanoreceptors in the skin mediate the perception of static pressure stimuli, while rapidly adapting skin receptors mediate swiftly changing (e.g., vibratory) stimuli. Background There are various skin receptors. Hairy skin, such as that encountered on the arm, contains at least four specialized mechanoreceptors, namely ...


3

What many drugs and compounds do is bind to cell receptors. These receptors then change shape and various things may happen in the cell as a result (including relaying a message to other cells). Something that binds to a receptor and causes activity is called an agonist. Something that binds to a receptor and causes a partial response is called a partial ...


3

I think it's best to break this question up in to two parts: What mutations account for red hair and fair skin in humans How might these same mutations affect pain sensation MC1R variants & red hair The MC1R gene encodes a transmembrane receptor protein (belonging to a very common family of receptors), called melanocortin 1 receptor. It also has ...


3

It's not that people didn't want to use hemagglutinin as a target for antivirals, it's that they haven't been able to get the antivirals through the approval process yet. There are a number of experimental inhibitors (see for example Progress of small molecular inhibitors in the development of anti-influenza virus agents) but the approval and licensing ...


2

There are five subunits to this receptor (5-HT3), which are encoded by the genes HTR3(A-D) and differentially expressed depending on cell location in the (human) body. In contrast to the information in the previous answer, my first source actually has shown HTR3A to be most highly expressed in the CNS. The others are almost exclusively found in cells of the ...


2

CB1 and CB2 are indeed particular genes which are present in neurons, but also liver and other tissues. The HGNC website is a good resource for questions like this - HGNC is the international organization that tries to unify and track gene names. The official gene names are CNR1 and CNR2 respectively. Gene names are a bit of a mess, since many genes have ...


2

Yes, it does cause lesions in rats, although I don't think it's been observed to do so in humans. See: http://www.druglib.com/druginfo/namenda/description_pharmacology/


2

In Drosophila, Toll receptors are used during embryonic development as well as innate immunity. See The Drosophila Toll Signaling Pathway by Valance, et. al. Toll-like Receptors are pattern recognition receptors found in organisms other than Drosophila that recognize common motifs found on pathogens. Toll receptors were first discovered in Drosophila and ...


2

Most NSAIDs derive their analgesic effects from inhibit the cyclooxygenase (COX) enzymes that produce the prostaglandin-H2 precursor to the prostaglandins that sensitize neurons to pain. Edit: With respect to where this takes place, the COX enzymes are expressed in inflamed tissues as well as constitutively in the stomach and kidney. The prostaglandins ...


2

I think it's deathly important to note how critical CD4 is for the activation of T-helper cells, and thus a myriad of downstream immune cells such as B cells: When an APC presents an antigen through its MHC-II molecules, the TCR-II complex must interact with the Ag-MHC complex to transduce an activating signal. Note that the T-helper TCR is composed of α/ß ...


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