Biological clocks fly into view.
Clocks are ubiquitous in today's society. In addition to their traditional homes on mantles, nightstands, and wrists, timepieces now appear on VCRs, computer screens, TVs, microwave ovens, and much more. Nature's fondness for clocks may be even more impressive, however. Scientists report in the Nov. 28 Science that the fruit fly harbors biological clocks in its head, thorax thorax, body division found in certain animals. In humans and other mammals it lies between the neck and abdomen and is also called the chest. The skeletal frame of the thorax is formed by the sternum (breastbone) and ribs in front and the dorsal vertebrae in back. , abdomen, leg bristles, wings, antennae, and proboscis proboscis
elongated, flexible feeding apparatus, formed of the fused mouthparts, in some insects. . "We were really shocked there were these light-resettable clocks throughout the animal," says Steve A. Kay of the Scripps Research Institute in La Jolla, Calif.
Biological clocks are the internal timekeepers; that generate circadian rhythms, the day-long cycles of activities. One clock has been well documented in the brains of many animals. Its rhythm governs several easily observable behaviors such as sleeping, and it has been considered the body's master clock. Yet investigators have found that other tissues seem to maintain their own biological clocks. For example, Jadwiga M. Giebultowicz of Oregon State University Oregon State University, at Corvallis; land-grant and state supported; coeducational; chartered 1858 as Corvallis College, opened 1865. In 1868 it was designated Oregon's land-grant agricultural college and was taken over completely by the state in 1885. in Corvallis and her colleagues have found biological clocks in the testes testes
Male reproductive organs (see reproductive system). Humans have two oval-shaped testes 1.5–2 in. (4–5 cm) long that produce sperm and androgens (mainly testosterone), contained in a sac (scrotum) behind the penis. of moths and in the fruit fly's Malpighian tubules, excretory ex·cre·to·ry
Of, relating to, or used in excretion.
pertaining to excretion.
see elimination behavior. organs similar to kidneys.
By linking the activity of per, a gene that acts as a gear in the fly's biological clock, to genes encoding fluorescent markers, Kay and his colleagues obtained striking visual evidence of daily cyclical activity in almost every fruit fly tissue studied. They could reset each clock by exposing isolated tissues to a new light-dark cycle. Rather than being controlled by the clock in the fly's brain, the other clocks may be governed independently by the day-night cycle, suggests Kay. "The master clock for the fruit fly is sunlight," he proposes.
The new work is "mind-boggling. It suggests that there are circadian circadian /cir·ca·di·an/ (ser-ka´de-an) denoting a 24-hour period; see under rhythm.
Relating to biological variations or rhythms with a cycle of about 24 hours. oscillators all over," says Michael Menaker of the University of Virginia in Charlottesville, who discovered that the mammalian retina has its own biological clock (SN: 4/20/96, p. 245). Unfortunately, adds Menaker, scientists still have few clues to why most of these clocks exist and whether they indeed act independently or form a hierarchy.
Kay and his colleagues now plan to repeat their fruit fly work in mammals by creating transgenic mice in which clock genes are linked to genes encoding fluorescent markers. They will also explore how the individual fly clocks perceive light. "It looks like the circadian photoreceptor photoreceptor /pho·to·re·cep·tor/ (-re-sep´ter) a nerve end-organ or receptor sensitive to light.
n. is not going to be a known visual pigment visual pigment
Any of the photopigments in the retinal cones and rods that absorb light and photochemically initiate the phenomenon of vision. ," says Kay.