of specific molecules (e.g., in DNA sequencing process). See also PROTEIN, FATS, LIGNANS,

IMMUNOASSAY, FLUORESCENCE, SEQUENCING (OF

DNA MOLECULES).

Near-Infrared Transmission (NIT) Refers to certain analytical instruments which shine light (possessing wavelengths between that of visible light and infrared spectrum) through samples (e.g., kernels of grain) in order to quickly determine the amounts of protein, fat, moisture, lignans, etc. present in the sample. See also PROTEIN, FATS, LIGNANS,

NEAR-INFRARED SPECTROSCOPY (NIR).

Necrosis Refers to cell death caused by physical injury to the cell (e.g., exposure to toxin, exposure to ultraviolet light, lack of oxygen,

etc.). See also CELL, TOXIN, RESPIRATION,

TUMOR NECROSIS FACTOR.

Neem Tree A tropical tree (Azadirachta indica) found in India, Somalia, Mauritania, Australia, and other tropical countries; that resists insect (e.g., whiteflies, mealybugs, aphids, mites) depradations and certain fungal diseases (rusts, powdery mildew, etc.) via secretions of liquids that contain Azadirachtin (an insect-repelling chemical). See also

AZADIRACHTIN, FUNGUS.

Negative Supercoiling Comprises the twisting of a duplex of DNA (deoxyribonucleic acid) in space in the opposite sense to the turns of the strands in the double helix. See

also DOUBLE HELIX.

Nematodes Microscopic roundworms, which are the most abundant multi-celled creatures on earth. They are primarily found living in soil. One nematode named Caenorhabditis elegans (C. elegans) is commonly used by scientists in genetics experiments, so a large base of knowledge about its genetics has been accumulated by the world’s scientific community. For example, of the nearly 300 “disease-causing” genes in the human genome, more than half of them have an analogous gene within the genome of C. elegans. One Antarctic nematode (Panagrolaimus davidi) is able to survive Antarctic winters by drying out and achieving a state of “suspended animation” (anhydrobiosis) for as long as thirty-nine years. See also

CELL, CAENORHABDITIS ELEGANS (C. ELEGANS),

GENETICS, GENE, GENOME, GENETIC MAP, MODEL

ORGANISM, SOYBEAN CYST NEMATODES (SCN),

CYSTX.

NEMS See NANOELECTROMECHANICAL SYSTEM

(NEMS).

Neoplasia New growth. See also NEOPLASTIC

GROWTH.

Neoplastic Growth A new growth of animal or plant tissue resembling (more or less) the tissue from which it arises but having distinct biochemical differences from the parent cell. The neoplastic tissue is a mutant version of the original and appears to serve no physiologic function in the same sense as did the original tissue. It may be benign or malignant (i.e., a cancerous tumor). See also

TUMOR, CANCER, SELECTIVE APOPTOTIC ANTI-

NEOPLASTIC DRUG (SAAND), METASTASIS.

Nerve Growth Factor (NGF) A protein produced by the salivary glands (and also in tumors) that greatly increases growth/reproduction of nerve cells and guides the formation of neural networks. In the brain, NGF is thought to increase the production of the messenger chemical, acetylcholine, by protecting and stimulating those neurons that produce acetylcholine. Because those (ace-

tylcholine-producing) neurons are typically N the first to be destroyed in an Alzheimer’s

disease victim, NGF holds potential to be used to counteract (some of) the effects of the disease.

NGF is also necessary for normal development of the hypothalamus, a brain structure that regulates a number of hormones. Human T cells appear to have receptors for NGF, which could explain the “mind–body connection” between a person’s emotional well-being and physical health (i.e., NGF may be a go-between for the brain and the immune system). NGF was discovered by Rita Levi-Montalcini in 1954. See also

GROWTH FACTOR, EPIDERMAL GROWTH FACTOR

(EGF), HYPOTHALAMUS, HORMONE, PROTEIN.

Nested PCR Refers to a specific PCR (polymerase chain reaction) technique of two con- secutive-run PCRs, in which the second PCR amplifies (i.e., makes multiple copies of) a DNA sequence within the product (amplicon) of the first PCR. See also POLYMERASE

CHAIN REACTION (PCR), POLYMERASE CHAIN REACTION (PCR) TECHNIQUE, SEQUENCE (OF A

© 2002 by CRC Press LLC

DNA MOLECULE), DEOXYRIBONUCLEIC ACID

(DNA), AMPLICON.

Neuraminidase (NA) A transmembrane (i.e., through the membrane) glycoprotein enzyme that appears in the (external) membrane of the influenza virus. See also

ENZYME, GLYCOPROTEIN, VIRUS.

Neuron Cells of the body’s nervous system, which transmit nerve impulses (electrical signals conducted by the flow of ions across the plasma membrane of neuron cells). Neurons are involved in controlling movement (known as motor control), emotions, and memory. There are approximately 100 billion neurons in the typical human brain. The nerve impulses within them move at a speed of approximately 400 kilometers per hour (300 miles per hour).

See also NEUROTRANSMITTER, ACETYLCHOLINE,

SEROTONIN, CELL, PARKINSON’S DISEASE, PLASMA MEMBRANE, ION, DENDRITES.

Neurotransmitter An organic, low molecular weight compound that is secreted from the (axon) terminal end of a neuron (in response to the arrival of an electrical impulse) into a liquid-filled gap that exists between neurons. The transmitter molecule then diffuses

Nacross the small gap and attaches to the next neuron. This attachment causes structural changes in the membrane of the neuron and initiates the conductance of an electrical impulse. In this way, an electrical impulse is transmitted (via this “cascade”) along a neuron network of which the neurons themselves do not physically touch.

A neurotransmitter serves to transmit a nerve impulse between different neurons. Examples of neurotransmitters include dopamine and norepinephrine. A shortage of dopamine in the brain causes the disease

known as Parkinson’s disease. See also

MOLECULAR WEIGHT, NEURON, SEROTONIN,

ACETYLCHOLINE, PARKINSON’S DISEASE, CASCADE,

DENDRITES.

Neutraceuticals See NUTRACEUTICALS. Neutriceuticals See NUTRACEUTICALS.

Neutrophils Phagocytic (ingesting, scavenging) white blood cells produced in the bone marrow. They ingest and destroy invading microorganisms and facilitate post-infection tissue repair. They can secrete collagenase and plasminogen activator. They are the

immune system’s “first line” of defense against invading pathogens, and large reserves are called forth within hours of the start of a “pathogen invasion.” See also

PATHOGEN, COLLAGENASE, MICROORGANISM.

New Drug Application See NDA (TO KOSEISHO),

NDA (TO FDA), MAA, IND, CANDA.

NIAID See NATIONAL INSTITUTE OF ALLERGY AND

INFECTIOUS DISEASES.

Nick A break in one strand of a doublestranded DNA molecule. One of the phosphodiester bonds between two adjacent nucleotides is ruptured. No bases are removed from the strand, it is just opened at

that point. See also DEOXYRIBONUCLEIC ACID

(DNA).

Nicotine-Adenine Dinucleotide (NAD) S e e

NAD.

Nicotine-Adenine Dinucleotide Phosphate (NADP) See NAD.

Nicotine-Adenine Dinucleotide Phosphate, reduced (NADPH) See NAD.

Nicotine-Adenine Dinucleotide, reduced (NADH) See NAD.

NIH See NATIONAL INSTITUTES OF HEALTH (NIH). NIHRAC See RECOMBINANT DNA ADVISORY COM-

MITTEE (RAC).

Ninhydrin Reaction A color reaction given by amino acids and peptides on heating with the chemical ninhydrin. The technique is widely used for the detection and quantitation (measurement) of amino acids and peptides. The concentration of amino acid in a solution (of hydrochloric acid) is proportional to the optical absorbance of the solution after heating it with ninhydrin. α-Amino acids give an intense blue color, and amino acids (such as proline) give a yellow color. One is able to determine concentration of a protein or peptide and also obtain an idea of the type of protein or peptide that is present.

See also ABSORBANCE (A), AMINO ACID, PEPTIDE.

Nitrate Bacteria See N I T R A T E S , N I T R I T E S ,

BACTERIA.

Nitrate Reduction The reduction of nitrate to nitrite or ammonia by an organism. See also

NITRATES, REDUCTION (IN A CHEMICAL REACTION),

NITRITES.

Nitrates Refers to nitrogen compounds that exist in a chemical form which plant roots are able to take in (i.e., utilized by the plant

© 2002 by CRC Press LLC

to make nitrogen-containing molecules such as proteins). Nitrates are produced from nitrogen:

•Taken out of the atmosphere by nitro- gen-fixing bacteria (living among the roots of legume plants such as the soybean, etc.)

•Taken out of nitrites (in soil) by nitrate bacteria

•Taken out of the atmosphere by bluegreen algae

See also PROTEIN, NITROGEN FIXATION, SOYBEAN PLANT, NITRITES.

Nitric Oxide Abbreviated NO, it is a molecule produced in the body of an organism, which can act as:

•A signaling molecule (e.g., to cause a firefly’s tail to begin the chemical reaction of luciferin with luciferase that results in the light emission known as bioluminescence)

•An oxidant utilized against pathogens by the immune system

•An instigator of (destructive) free radicals

•An inducer of genes (e.g., in soybean plants) that cause production of certain chemical compounds which protect the organism (e.g., soybean plant) from bacterial diseases

As a signaling molecule, or “messenger molecule,” nitric oxide is utilized by the human body for control of blood pressure (i.e., when the endothelial cells that line blood vessels produce NO that causes neighboring smooth-muscle cells to relax so entire blood vessel dilates; thereby lowering blood pressure). Nitric oxide is also utilized by the human body for immune system regulation, and its synthesis in macrophages is required for macrophages to kill pathogens and tumor cells (by oxidizing them after the macrophage has engulfed them).

During the 1980s, John Garthwaite and Solomon H. Snyder showed that nitric oxide is an important messenger molecule utilized in neural signaling (i.e., NO is an important signaling molecule in the human brain).

Nitric oxide increases the effectiveness of reactive free radicals (e.g., superoxide O2) in killing off any infected cells within a soybean plant. Nitric oxide also induces certain genes to code for the production of certain chemical compounds that protect the soybean plant from bacterial plant diseases. See also SIG-

NALING MOLECULE, SIGNALING, OXIDIZING AGENT,

PATHOGEN, IMMUNE RESPONSE, HUMAN SUPEROX-

IDE DISMUTASE (hSOD), SIGNAL TRANSDUCTION,

NITRIC OXIDE SYNTHASE, SOYBEAN PLANT, PRO-

TEIN, INDUCERS, GENE, CODING SEQUENCE, FREE

RADICAL, ENDOTHELIAL CELLS, ENDOTHELIUM,

MACROPHAGE, PATHOGEN, BACTERIA, TUMOR,

NEUROTRANSMITTER, BIOLUMINESCENCE.

Nitric Oxide Synthase An enzyme that catalyzes the reaction which the body (of animals or plants) utilizes to make nitric oxide from L-arginine (via cleavage, off that molecule). The cofactor for that reaction is nic- otine-adenine dinucleotide phosphate

(NADP). See also ENZYME, NITRIC OXIDE,

COFACTOR, NAD (NADH, NADP, NADPH), ARGININE

(arg), LEVOROTARY (L) ISOMER, HYDROLYTIC

CLEAVAGE, ENDOTHELIAL CELLS, ENDOTHELIUM,

MACROPHAGE.

Nitrification The oxidation of ammonia (e.g., N from ammonia-containing substances such

as liquid wastes excreted by animals, decomposed animals and plants, etc.) to nitrates by a microorganism. See also N I T R A T E S ,

NITRITES, OXIDATION (chemical reaction).

Nitrifying Bacteria See NITRITES.

Nitrilase An enzyme that catalyzes the degradation (breaking down) of bromoxynil (an active ingredient in some herbicides). Nitrilase is naturally produced in the soil bacteria Klebsiella pneumoniae subs. Ozaenae. If a gene (called BXN) that codes for the production of nitrilase is inserted via genetic engineering into crop plants, the resultant plant production of nitrilase would enable such plants to survive post-emergence applications of bromoxynil-containing herbicides.

See also ENZYME, BACTERIA, BROMOXYNYL,

GENE, CODING SEQUENCE, GENETIC ENGINEERING.

Nitrites Refers to nitrogen compounds that exist in a chemical form which plant roots are unable to take in. After conversion to nitrates via internal respiration by nitrate bacteria (in soil), the nitrates can be taken in

© 2002 by CRC Press LLC

by plant roots (i.e., utilized by the plant to make nitrogen-containing molecules such as proteins). Nitrites are made (via internal respiration) by nitrifying bacteria (e.g., in soil) from ammonia-containing substances (e.g., liquid wastes excreted by animals, decomposed animals and plants, etc.). See also

NITRATES, PROTEIN, RESPIRATION.

Nitrogen Cycle The cycling of various forms of biologically available nitrogen through the plant, animal, and microbial worlds (kingdoms), as well as the atmosphere and

geosphere. See also NITRATES, NITRITES, NITRIFICATION, DENITRIFICATION, NITROGEN FIXATION.

Nitrogen Fixation Conversion of atmospheric nitrogen (N2) into ammonia; a soluble, biologically available form (nitrates). The conversion is carried out by nitrogen-fixing organisms (e.g., Rhizobium bacteria) which live symbiotically in the roots of legume plants, e.g., alfalfa or soybeans. This is one of nature’s ways of fertilizing [e.g., traditional varieties of soybeans typically leave approximately 40 pounds of residual nitrogen per acre (44kg) in fields at the end of the growing season]. When not enough

Nnitrogen fixation occurs (when only nonlegume plants are grown), soil is not able to produce maximum crop yields and farmers may need to spread fixed nitrogen onto the field in the form of the fertilizer anhydrous ammonia, ammonium nitrate, or sodium nitrate. See also NITRATES, SYMBIOTIC,

GENISTEIN (Gen), BACTERIA, SOYBEAN PLANT,

NITROGENASE SYSTEM, NITROGEN CYCLE, ISOFLA-

VONES, HEMAGGLUTININ (HA), NODULATION.

Nitrogen Metabolism See GLUTAMATE DEHYDRO-

GENASE.

Nitrogenase System A system of enzymes capable of reducing atmospheric nitrogen to ammonia in the presence of ATP. See also

REDUCTION (IN A CHEMICAL REACTION), ENZYME,

NITROGEN FIXATION.

NO See NITRIC OXIDE.

“No-Till” Crop Production See NO-TILLAGE

CROP PRODUCTION.

No-Tillage Crop Production A methodology of crop production in which the farmer utilizes virtually no mechanical cultivation (i.e., only one pass over the field, with a planter; instead of the conventional four

passes per year with mechanical cultivator equipment plus one pass with planter, used for traditional crop production). This reduction in field soil disturbance leaves more carbon in the soil (thereby reducing “greenhouse gases” in the atmosphere), leaves more earthworms (Eisenia foetida) per cubic foot or per cubic meter living in the topsoil, and reduces soil compaction (i.e., the reduction of interstitial spaces between individual soil particles); thereby increasing the fertility of such “no till” farm fields.

The plant residue remaining on the field’s surface helps to control weeds and reduce soil erosion (by 90–95% vs. traditional mechanical tillage), and it also provides sites for insects to shelter and reproduce, leading to a need for increased insect control via methods such as inserting a Bacillus thuringiensis

(B.t.) gene into certain crop plants or utilizing integrated pest management (IPM). But, if a farmer needs to apply synthetic chemical pesticides, the plant residue remaining on the field’s surface helps to cause breakdown (into substances such as carbon dioxide and water) of pesticides. That is because that plant residue helps to retain moisture in the field-sur- face environment, thereby enhancing growth of the microorganisms that help break down pesticides. Use of No-Tillage Crop Production (methodology) helps farmers to reduce the incidence of certain plant diseases such as white mold disease. See also INTEGRATED PEST

MANAGEMENT (IPM), CORN, GLOMALIN, SOYBEAN

PLANT, BACILLUS THURINGIENSIS (B.t.), GENE,

GENETIC ENGINEERING, EUROPEAN CORN BORER

(ECB), HELICOVERPA ZEA (H. ZEA), CORN ROOT-

WORM, COLD HARDENING, MICROORGANISM, LOW-

TILLAGE CROP PRODUCTION, EARTHWORMS, WHITE MOLD DISEASE.

Nod Gene See NODULATION.

Nodulation The process in which certain strains of soil-dwelling Rhizobium bacteria colonize the roots of specific plants (i.e., the legumes) such as soybean (Glycine max L.) or alfalfa. As part of that process:

•The Rhizobium bacteria are attracted to the vicinity of the plant’s roots. For the soybean plant (Glycine max L.), that is accomplished by the plant synthesizing

© 2002 by CRC Press LLC