|Medical Dictionary - Dictionary of Medicine and Human Biology|
A technique for investigating and recording conditions and procedures involving small objects that ordinarily would be inspected through a loupe rather than a microscope. [photo- + G. makros, large, + grapho, to write]
Morbid or exaggerated desire for light. [photo- + G. mania, frenzy]
An instrument designed to measure the intensity of light or to determine the light threshold. [photo- + G. metron, measure] flame p. an instrument that uses flame emission spectrophotometry to measure the intensity and other properties of light. flicker p. an instrument that compares two variable visual stimuli through control of the frequency of a flickering light.
The measurement of the intensity of light.
An enlarged photograph of an object viewed with a microscope, as distinguished from microphotograph. SYN: micrograph (2) . [photo- + G. mikros, small, + graphe, a record]
The production of a photomicrograph. SYN: micrography (3) .
Clonic spasms of muscles in response to visual stimuli. [photo- + G. mys, muscle, + klonos, confused motion] hereditary p. [MIM*172500] p. associated with diabetes mellitus, deafness, nephropathy, and cerebral dysfunction; autosomal dominant inheritance.
photon (hν, γ) (fo′ton)
In physics, a corpuscle of energy or particle of light; a quantum of light or other electromagnetic radiation.
Any disease caused by exposure to light. [photo- + G. pathos, suffering]
The characteristic energies of photons emitted by a radionuclide, used to set scanning parameters.
Capable of both receiving and perceiving light.
The periodic (seasonal or diurnal) activities, behavior, or changes in plants or animals brought about by the action of light.
SYN: photalgia. [photo- + G. phobos, fear]
Relating to or suffering from photophobia.
In bacteriology, the organ producing intracellular bioluminescence in certain organisms. [photo- + G. phoros, bearing]
See extracorporeal p.. extracorporeal p. destruction of cells separated from blood in an extracorporeal flow system by ultraviolet activation of chemotherapeutic agents such as psoralens.
Formation of ATP as a result of absorption of light.
Keratoconjunctivitis caused by ultraviolet energy, as in snow blindness, exposure to an ultraviolet lamp, arc welding, or the short circuit of a high-tension electric current. SEE ALSO: photoretinopathy. [photo- + G. ophthalmos, eye]
SYN: photopic vision. [photo- + G. opsis, vision]
Pertaining to p. vision.
A subjective sensation of lights, sparks, or colors due to electrical or mechanical stimulation of the ocular system. SEE ALSO: Moore lightning streaks, under streak. SYN: photopsy. [photo- + G. opsis, vision]
The protein moiety (opsin) of the pigment (iodopsin) in the cones of the retina.
Sneezing on looking at a light, especially a bright light ( e.g., sunlight), a reflex of which the neuroanatomic pathways are debated; autosomal dominant transmission. SYN: photic-sneeze reflex. [photo- + G. ptarmos, a sneezing, + -osis, condition]
Treatment of cancer by intravenous injection of a photosensitizing agent, such as hematoporphyrin, followed by exposure to visible light of superficial tumors or of deep tumors by a fiberoptic probe. SYN: photochemotherapy, photodynamic therapy, p. therapy.
A reaction caused or affected by light; e.g., a photochemical reaction, photolysis, photosynthesis, phototropism, thymine dimer formation.
Activation by light of something or of some process previously inactive or inactivated; e.g., pyrimidine dimers, formed in polynucleic acids by the action of UV light, can be monomerized by UV light of a different wavelength via DNA photolyase.
Functioning as a photoreceptor.
photoreceptor (fo′to-re-sep′ter, tor)
A receptor that is sensitive to light, e.g., a retinal rod or cone. SYN: photoceptor. [photo- + L. re-cipio, pp. -ceptus, to receive, fr. capio, to take]
Light-enhanced respiration in photosynthetic organisms; i.e., light increases O2 utilization.
A macular burn from excessive exposure to sunlight or other intense light ( e.g., the flash of a short circuit); characterized subjectively by reduced visual acuity. SEE ALSO: solar maculopathy. SYN: electric retinopathy, solar retinopathy. [photo- + retina, + G. pathos, suffering]
1. An abnormally heightened reactivity of the skin to sunlight. 2. Responding to light, e.g., as by a photocell. [photo + L. sensus, a feeling, fr. sentio, to feel]
Abnormal sensitivity to light, especially of the eyes. For example, light may irritate the eyelids, conjunctiva, cornea or, in excess, the retina; when scattered by a cataractous lens light may produce glare; it can produce a migraine headache or a temporary exotropia. See photophobia, photalgia, photesthesia.
1. Sensitization of the skin to light, usually due to the action of certain drugs, plants, or other substances; may occur shortly after administration of the drug (phototoxic sensitivity), or may occur only after a latent period of from days to months (photoallergic sensitivity, or photoallergy). 2. SYN: photodynamic sensitization.
photosensor (fo′to-sen′ser, sor)
A device designed to respond to light and to transmit resulting impulses for interpretation, movement, or operating control. See sensor.
Not subject to change upon exposure to light.
Device that converts sound into flashes of light; used for continuous observation of the fetal heart.
Exposure to intense illumination. SEE ALSO: p. test.
1. The compounding or building up of chemical substances under the influence of light. 2. The process by which green plants, using chlorophyll and the energy of sunlight, produce carbohydrates from water and carbon dioxide, liberating molecular oxygen in the process. [photo- + G. synthesis, a putting together] bacterial p. a primitive form of p. observed in some bacteria using only one photosystem and some reducing agent other than water.
Reaction of living protoplasm to the stimulus of light, involving bodily motion of the whole organism toward (positive p.) or away from (negative p.) the stimulus. Cf.:phototropism. [photo- + G. taxis, orderly arrangement]
Treatment of disease by means of light rays. SYN: light treatment.
Relating to radiant heat. [photo- + G. therme, heat]
An electronic device in radiography that measures the radiation that has passed through the patient and terminates the x-ray exposure when it is sufficient to form an image.
Relating to, characterized by, or causing phototoxicity.
The condition resulting from an overexposure to ultraviolet light, or from the combination of exposure to certain wavelengths of light and a phototoxic substance. SEE ALSO: photosensitization. [photo- + G. toxikon, poison]
An organism that uses light for its energy needs. Cf.:photoautotroph, photoheterotroph, photolithotroph.
Movement of a part of an organism toward (positive p.) or away from (negative p.) the stimulus of light. Cf.:phototaxis. [photo- + G. trope, a turning]
The passage of phosphorescent urine. [photo- + G. ouron, urine]
Abbreviation for panhypopituitarism.
Barrel-shaped enlargement of the spindle associated with formation of the new cell membrane during telophase in plant cells. [G. phragma, hedge, enclosure, + plasso, to form]
1. SYN: diaphragm (1) . 2. The mind. [G. p., the diaphragm, mind, heart (as seat of emotions)]
1. SYN: psychalgia (1) . 2. Pain in the diaphragm. [phren- + G. algos, pain]
SYN: phreniclasia. [phren- + G. emphraxis, a stoppage]
1. Frenzied; maniacal. 2. An individual exhibiting such behavior. [G. phrenitikos, frenzied]
1. The diaphragm. 2. The mind. See phreno-. [G. phren, the diaphragm, mind, heart (as seat of emotions]
1. SYN: diaphragmatic. 2. Relating to the mind.
Exsection of a portion of the phrenic nerve, to prevent reunion such as may follow phrenicotomy. SYN: phrenectomy, phrenicoexeresis, phreniconeurectomy. [phreni- + G. ektome, excision]
Crushing of a section of the phrenic nerve to produce a temporary paralysis of the diaphragm. SYN: phrenemphraxis, phrenicotripsy. [phreni- + G. klasis, a breaking away]
Relating to the diaphragm and the colon. SYN: phrenocolic.
SYN: phrenicectomy. [phrenico- + G. exairesis, a taking out, fr. haireo, to take, grasp]
Relating to the diaphragm and the stomach. SYN: phrenogastric.
Relating to the diaphragm and the glottis; denoting a spasm involving the diaphragm and the vocal cords.
Relating to the diaphragm and the liver. SYN: phrenohepatic.
Relating to the diaphragm and the spleen.
Section of the phrenic nerve in order to induce unilateral paralysis of the diaphragm, which is then pushed up by the abdominal viscera and exerts compression upon a diseased lung. [phrenico- + G. tome, incision]
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