4-Biology-Techniques

animal model

Animal diseases can model human diseases {animal model} {model, animal}. Germ-free animals are useful.

variables

Disease progress and outcome depend on species, strain, genotype modifications, gender, and age. Disease agents and treatments have different locations and administration methods.

problems

Animals contract other diseases regularly in laboratory settings, so animals must have no bacteria, such as Helicobacter and Camphlylobacter, or worms, such as Helminthes. Outside organisms can elicit immunologic, inflammatory, and cancerous effects to obviate experiment.

association study

Studies {association study} can compare allele frequency in disease and control populations. Frequency difference indicates that allele relates to disease. Genetic-linkage algorithms compare disease and control allele frequencies to find marker locus. Studies can compare allele frequencies among phenotypes.

carbon dating

Carbon-isotope ratios can date objects up to 100,000 years old {carbon dating}|.

instrument

Mass spectroscopy can measure isotope amounts in very small samples.

location

Lower-atmosphere carbon dioxide has radioactive carbon-14 {radiocarbon} to non-radioactive carbon-12 ratio. Living things have same carbon-isotope ratio as lower atmosphere.

time

Lower-atmosphere carbon-isotope ratio varies over time. Measuring air trapped in glaciers at different depths shows ratios at past times. Carbon-isotope ratio decreases after organisms die, because carbon-14 decays to nitrogen-14. Comparing current reduced ratio to atmosphere ratio at death indicates time of death.

age

Carbon dating is only useful up to 100,000 years ago, because almost all carbon-14 decays in 100,000 years.

changes

Older carbon-dating methods needed more mass and used fire ashes or other organic materials adjacent to formerly living things, not living things themselves. Older carbon-dating methods assumed that atmospheric carbon-isotope ratio is constant. Because ratios actually changed, carbon-dating dates in scientific literature before 1990 are typically too recent. For example, earlier-reported -9000 is actually -11000 or 13,000 years ago.

calibration

Actual lower-atmosphere carbon-isotope ratios, measured at different glacier depths, can find correct dates {calibrated carbon dating}.

dissection

Techniques {dissection}| can open plants and animals to observe parts.

gene insertion

Shooting gold or tungsten particles carrying genes into cereal seeds {gene insertion} can cause gene insertion into cereal DNA.

leaf disk technique

Agrobacterium tumefaciens can attach to plant leaves and then transfer DNA, including foreign genes, into leaves {leaf disk technique}.

limb movement

Placing lights on joints and limbs allows filming limb movements {limb movement}.

monoclonal antibody

Injecting antigens into mice or rats causes immune responses and makes antibodies {monoclonal antibody}| in spleen lymphocytes.

hybrid cells

In cell culture, lymphocytes can mix with myeloma cell lines to make hybrid cells {hybridoma}. Polyethylene glycol helps hybridization.

screening

Screening can find hybrid cells with large antibody quantities.

antibodies

Rituxan works against lymphoma.

Herceptin {trastuzumab} works against breast cancer. Epidermal-growth-factor receptors (EGFR) make dimerization signals, which tell cells to divide. Herceptin binds to HER2 cell-surface epidermal-growth-factor receptors and prevents dimerization signals. Dimercept binds to HER cell-surface-receptor dimerization sites. Lapatinib kinase inhibitor inhibits HER2 receptors.

Kinase inhibitors inhibit PI3K, AKT, and mTOR in cell-survival pathway.

Letrozole aromatase inhibitor inhibits estrogen synthesis. Tamoxifen aromatase inhibitor inhibits estrogen and progesterone synthesis.

Bevacimuzab inhibits tumor blood-vessel formation at VEGF receptors.

Monoclonal antibodies can inhibit IGF-1 receptors.

nanobodies

Llamas and camels make half their antibodies {nanobody} using only heavy chains, which supply variable segments.

optical coherence tomography

Coherent light sources can split into reflected beams and beams that enter tissue, and then beams can interfere {optical coherence tomography}.

surface plasmon resonance

Techniques {surface plasmon resonance} (SPR) can measure protein site-binding strength.

4-Biology-Techniques-Nerve

axon flow

Squeezing nerve fibers causes axoplasm to accumulate on both sides, showing that nerve-fiber axoplasm flows {axon flow} in both directions.

Nauta technique

Techniques {Nauta technique} can stain degenerating axons with silver. First, electrodes stimulate neurons with electric current, or fine pipettes stimulate neurons with chemicals. Then fine pipettes inject dye into cells. After axon cutting, dye blackens dying-axon branches.

positron emission tomography

Techniques {positron emission tomography} (PET) can use radioactive oxygen or carbon isotopes to measure cerebral blood flow or metabolic activity. Oxygen isotopes in glucose or neurotransmitters emit positrons as they decay. Patients receive radioactive tracers by injection or in food. Scanners localize radioactivity to within several millimeters and within one minute. Localized radioactivity shows increased oxygen-metabolism and glucose-metabolism sites. Brain blood flow varies with metabolic activity, so PET indicates locations with increased blood flow.

xenon

Alternatively, patients can receive radioactive xenon by injection into blood. The most active neurons become the most radioactive.

carbon 14

Carbon(14) 2-deoxyglucose is similar to glucose. Neurons can absorb the radioactive compound but cannot metabolize it. Neurons that absorb the most radioactivity are the most metabolically active.

retrograde marking

Techniques {immunohistofluorescence} {retrograde marking} [1970] can stain neurons backward from injection site using horseradish peroxidase, colloidal gold wheat-germ agglutin, and fluorescent dyes.

single channel recording

Techniques {single channel recording} {patch clamping} can measure single-neuron electrical activity.

single photon emission computed tomography

Techniques {single photon emission computed tomography} (SPECT) can measure cerebral blood flow or metabolic activity, using light.

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Date Modified: 2022.0225