The rat suprachiasmatic nucleus is a clock for all seasons.

Seasonal changes of daylength (photoperiod) affect the expression of hormonal and behavioral circadian rhythms in a variety of organisms. In mammals, such effects might reflect photoperiodic changes in the circadian pace-making system [located in the suprachiasmatic nucleus (SCN) of the hypothalamus] that governs these rhythms, but to date no functionally relevant, intrinsic property of the SCN has been shown to be photoperiod dependent. We have analyzed the temporal regulation of light-induced c-fos gene expression in the SCN of rats maintained in long or short photoperiods. Both in situ hybridization and immunohistochemical assays show that the endogenous circadian rhythm of light responsiveness in the SCN is altered by photoperiod, with the duration of the photosensitive subjective night under the short photoperiod 5-6 h longer than under the long photoperiod. Our results provide evidence that a functional property of the SCN is altered by photoperiod and suggest that the nucleus is involved in photoperiodic time measurement.

Catalogue of the very select and valuable library of William Roscoe, Esq. : which will be sold by auction by Mr. Winstanley at his rooms in Marble Street, Liverpool, on Monday the 19th of August, and thirteen following days (Sundays excepted) : the sale to begin at eleven o'clock precisely.

Includes index of 15th century printers.

Terry clock chronology /

"Sources": p. iv-v.

Laying of the cornerstone of Gregory Hall University of Illinois. Saturday morning June tenth nineteen thirty-nine eleven o'clock.

Mode of access: Internet.

A rudimentary treatise on clock and watch making : with a chapter ou church clocks... /

Mode of access: Internet.

Mystery of Edwin Drood; Master Humphrey's clock, and Sketches by "Boz."

The mystery of Edwin Drood.--Master Humphrey's clock, and other pieces.--Sketches by Boz.--Holiday romance.--George Silverman's explanation.

Catalogue of 1098 standard clock and zodiacal stars.

Mode of access: Internet.

Germany puts the clock back

"The story of the collapse of German democracy through the Reichstag elections of November 6."--Foreword.

A candle clock, recto, folio from Kitab fi ma`arifat al-hiyal al-handisaya (The book of knowledge of ingenious mechanical devices) Automata by al-Jazari

1 ft. 1/8 in.x 8 5/8 in.; ink, opaque watercolor and gold on paper

Automata by al-Jazari, The face of a water clock with Zodiac signs, folio from the Kitab fi ma'arifat al-hiyal al-handisaya (the book of knowledge of ingenious mechanical devices) Automata by al-Jazari

1 ft. 13/32 in.x 8 5/8 in.; ink, opaque watercolor and gold on paper

verso: text and illustration: The water clock of the drummers from Kitab fi ma'arifat al-hiyal al-handisaya (The book of knowledge of ingenious mechanical devices) Automata by al-Jazari)

ink, opaque watercolor and gold on paper

The Elephant Clock", from a Book of the Knowledge of Ingenious Mechanical Devices by al-Jazar

11 13/16 in.x 7 3/4 in.; ink, opaque watercolor, and gold on paper

Catalogue of the collection of Greek coins in gold, silver, electrum and bronze, of a late collector ... which will be sold by auction, by messrs. Sotheby, Wilkinson & Hodge ... on Monday, the 28th day of May, 1900, and three following days, at one o'clock precisely.

Mode of access: Internet.