Vitamin B2-based blue-light photoreceptors in the retinohypothalamic tract as the photoactive pigments for setting the circadian clock in mammals

In mammals the retina contains photoactive molecules responsible for both vision and circadian photoresponse systems. Opsins, which are located in rods and cones, are the pigments for vision but it is not known whether they play a role in circadian regulation. A subset of retinal ganglion cells with direct projections to the suprachiasmatic nucleus (SCN) are at the origin of the retinohypothalamic tract that transmits the light signal to the master circadian clock in the SCN. However, the ganglion cells are not known to contain rhodopsin or other opsins that may function as photoreceptors. We have found that the two blue-light photoreceptors, cryptochromes 1 and 2 (CRY1 and CRY2), recently discovered in mammals are specifically expressed in the ganglion cell and inner nuclear layers of the mouse retina. In addition, CRY1 is expressed at high level in the SCN and oscillates in this tissue in a circadian manner. These data, in conjunction with the established role of CRY2 in photoperiodism in plants, lead us to propose that mammals have a vitamin A-based photopigment (opsin) for vision and a vitamin B2-based pigment (cryptochrome) for entrainment of the circadian clock.

Protein kinase CK2 interacts with and phosphorylates the Arabidopsis circadian clock-associated 1 protein

The circadian clock-associated 1 (CCA1) gene encodes a Myb-related transcription factor that has been shown to be involved in the phytochrome regulation of Lhcb1*3 gene expression and in the function of the circadian oscillator in Arabidopsis thaliana. By using a yeast interaction screen to identify proteins that interact with CCA1, we have isolated a cDNA clone encoding a regulatory (β) subunit of the protein kinase CK2 and have designated it as CKB3. CKB3 is the only reported example of a third β-subunit of CK2 found in any organism. CKB3 interacts specifically with CCA1 both in a yeast two-hybrid system and in an in vitro interaction assay. Other subunits of CK2 also show an interaction with CCA1 in vitro. CK2 β-subunits stimulate binding of CCA1 to the CCA1 binding site on the Lhcb1*3 gene promoter, and recombinant CK2 is able to phosphorylate CCA1 in vitro. Furthermore, Arabidopsis plant extracts contain a CK2-like activity that affects the formation of a DNA–protein complex containing CCA1. These results suggest that CK2 can modulate CCA1 activity both by direct interaction and by phosphorylation of the CCA1 protein and that CK2 may play a role in the function of CCA1 in vivo.

Light-induced phase-delay of the chicken pineal circadian clock is associated with the induction of cE4bp4, a potential transcriptional repressor of cPer2 gene

The chicken pineal gland contains the autonomous circadian oscillator together with the photic-input pathway. We searched for chicken pineal genes that are induced by light in a time-of-day-dependent manner, and isolated chicken homolog of bZIP transcription factor E4bp4 (cE4bp4) showing high similarity to vrille, one of the Drosophila clock genes. cE4bp4 was expressed rhythmically in the pineal gland with a peak at very early (subjective) night under both 12-h light/12-h dark cycle and constant dark conditions, and the phase was nearly opposite to the expression rhythm of cPer2, a chicken pineal clock gene. Luciferase reporter gene assays showed that cE4BP4 represses cPer2 promoter through a E4BP4-recognition sequence present in the 5′-flanking region, indicating that cE4BP4 can down-regulate the chick pineal cPer2 expression. In vivo light-perturbation studies showed that the prolongation of the light period to early subjective night maintained the high level expression of the pineal cE4bp4, and presumably as a consequence delayed the onset of the induction of the pineal cPer2 expression in the next morning. These light-dependent changes in the mRNA levels of the pineal cE4bp4 and cPer2 were followed by a phase-delay of the subsequent cycles of cE4bp4/cPer2 expression, suggesting that cE4BP4 plays an important role in the phase-delaying process as a light-dependent suppressor of cPer2 gene.

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.

World Beats : Beat Generation Writing and the Worlding of U.S. Literature /

A study of the Beat-era writers in a global context. This title was made Open Access by libraries from around the world through Knowledge Unlatched.

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 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.

Catalogue of the private library of the late Mr. A.A. Smets, Savannah, Ga. : comprising one of the most valuable and extensive collections of books ever offered to the American public : containing very rare and elegant editions of early printed works, ranging from the XV. century : also, many early manuscripts and missals, with gorgeous illuminations : a large assortment of modern illustrated works, standard biographies, travels, histories, etc., etc., of the best editions : the whole to be sold by auction, at the Clinton Hall Book Salerooms and Art Galleries, Leavitt, Strebeigh & Co., auctioneers, Monday, May 25th, and following days, commencing at 4 o'clock P.M. each day.

"A southern library. A statement read before the New England historical and genealogical society ... Oct. 5, 1859" (4 p., bound at end of copy 1) relates to the present library.