Localization of the clock controlling circadian rhythms in the first neuropile of the optic lobe in the housefly

2001 ◽  
Vol 204 (19) ◽  
pp. 3303-3310
Author(s):  
Monika Bałys ◽  
Elżbieta Pyza
Keyword(s):  
Circadian Rhythms ◽  
Musca Domestica ◽  
Compound Eye ◽  
Optic Lobe ◽  
Continuous Light ◽  
Constant Darkness ◽  
Cross Sectional ◽  
Circadian Oscillators ◽  
L1 And L2 ◽  
The Brain

SUMMARYThe visual system of a fly expresses several circadian rhythms that have been detected in the photoreceptors of the compound eye and in the first neuropile, the lamina, of the underlying optic lobe. In the lamina, axons of two classes of interneuron, L1 and L2, exhibit cyclical size changes, swelling by day and shrinking by night. These rhythmic size changes may be generated by circadian oscillators located inside and/or outside the optic lobe. To localize such oscillators, we have examined changes in the axonal cross-sectional areas of L1 and L2 within the lamina of the housefly (Musca domestica) under conditions of 12 h of light and 12 h of darkness (LD12:12), constant darkness (DD) or continuous light (LL) 24 h after the medulla was severed from the rest of the brain. After the lesion, the axon size changes of L1 and L2 were maintained only in LD conditions, but were weaker than in control flies. In DD and LL conditions, they were eliminated. This indicates that circadian rhythms in the lamina of a fly are generated central to the lamina and medulla neuropiles of the optic lobe. Cyclical changes of light and darkness in LD conditions are still able, however, to induce a weak daily rhythm in the axon sizes of L1 and L2.

Continuous light or darkness and circadian periodic mitosis and metabolism in C and D8 mice

1961 ◽  
Vol 201 (2) ◽  
pp. 227-230 ◽  
Author(s):  
Franz Halberg ◽  
Cyrus P. Barnum
Keyword(s):  
Cell Division ◽  
Circadian Rhythms ◽  
Deoxyribonucleic Acid ◽  
Acid Metabolism ◽  
Specific Activity ◽  
Continuous Light ◽  
Liver Parenchyma ◽  
Constant Light ◽  
Constant Darkness ◽  
Spot Check

In immature C mice exposed first to alternating 12 hr of light and 12 hr of darkness (LD), and maintained thereafter in constant darkness for several days, the circadian rhythms in hepatic and pinnal mitosis are demonstrable by spot checks made at the approximate times of LD-synchronized peak and trough. Spot checks at same times in mice of same stock and age, kept for several days in constant light, reveal the cell division rhythm of liver parenchyma, but not that of pinnal epidermis. In immature D8 mice kept for several days in constant darkness, rhythms in hepatic mitosis, phospholipid, ribonucleic and deoxyribonucleic acid metabolism persist, while cell division rhythm in ear pinna of same animals is not detectable with the particular spot check used. In mice of same stock and age, on the 4th day in constant light, a significant rhythm persists in the relative specific activity of the hepatic phospholipid; timing of this metabolic cellular rhythm is drastically desynchronized from the reference standard of a 24-hr clock. Data reveal persistence of some mitotic and metabolic circadian rhythms under conditions studied, with phase drifts or phase shifts of these rhythms occurring both in relation to the 24-hr clock and among the rhythms themselves. These changes in external and internal timing of a circadian system are more extensive in constant light than in constant darkness.

Light-induced and circadian changes in the compound eye of the haematophagous bug Triatoma infestans (Hemiptera: Reduviidae)

2002 ◽  
Vol 205 (2) ◽  
pp. 201-210
Author(s):  
Carolina E. Reisenman ◽  
Teresita C. Insausti ◽  
Claudio R. Lazzari
Keyword(s):  
Compound Eye ◽  
Proximal Region ◽  
Triatoma Infestans ◽  
Pigment Cells ◽  
Constant Darkness ◽  
Light Conditions ◽  
Dynamic Changes ◽  
Circadian Oscillators ◽  
Direct Light ◽  
Open Rhabdom

SUMMARY We analysed dynamic changes in the ommatidial structure of the compound eyes of Triatoma infestans. This nocturnal insect possesses open-rhabdom eyes, in which a ring of six rhabdomeres from retinula cells 1–6 (R1–6) surrounds a central pair of rhabdomeres from retinula cells 7 and 8 (R7–8). Screening pigments are located in all the photoreceptors and in the primary (PPC) and secondary (SPC) pigment cells. During the day, pigments within R1–6 and the PPCs form a small ‘pupil’ above the rhabdom and pigments within R7–8 are clustered around the central rhabdomere, allowing light to reach only the central rhabdomere. At night, the ‘pupil’ widens, and pigments inside R7–8 concentrate in the proximal region of the cells, allowing light to reach the peripheral rhabdomeres. In addition, the distance between the cornea and the rhabdom decreases. These rhythmic changes adapt the sensitivity of the eye by controlling the amount of light reaching and travelling within the rhabdom. Furthermore, the rhythm persists under conditions of constant darkness (DD), i.e. it is controlled by an endogenous oscillator. Remarkably, there are differences in pigment movements between the retinula cells of a single ommatidium. The migration of pigments in R1–6 is regulated by a circadian input, while that in R7–8 is regulated by both direct light and circadian inputs. The rhythm vanishes under constant-light conditions (LL). In this species, the circadian rhythm of photonegative behaviour persists in both DD and LL conditions, suggesting that these two rhythms, in retinal morphology and visual behaviour, may be generated by different circadian oscillators.

scholarly journals Food-entrained circadian rhythms are sustained in arrhythmic Clk/Clk mutant mice

2003 ◽  
Vol 285 (1) ◽  
pp. R57-R67 ◽  
Author(s):  
SiNae Pitts ◽  
Elizabeth Perone ◽  
Rae Silver
Keyword(s):  
Circadian Rhythms ◽  
Clock Gene ◽  
Wheel Running ◽  
Mutant Mice ◽  
Circadian Oscillators ◽  
Daily Food ◽  
Food Anticipatory Activity ◽  
Anticipatory Activity ◽  
The Brain ◽  
Clock Protein

Daily scheduled feeding is a potent time cue that elicits anticipatory activity in rodents. This food-anticipatory activity (FAA) is controlled by a food-entrainable oscillator (FEO) that is distinct from light-entrained oscillators of the suprachiasmatic nucleus (SCN). Circadian rhythms within the SCN depend on transcription-translation feedback loops in which CLOCK protein is a key positive regulator. The Clock gene is expressed in rhythmic tissues throughout the brain and periphery, implicating its widespread involvement in the functioning of circadian oscillators. To examine whether CLOCK protein is also necessary for the FEO, the effect of daily food restriction was studied in homozygous Clock mutant ( Clk/Clk) mice. The results show that Clk/Clk mutant mice exhibit FAA, even when their circadian wheel-running behavior is arrhythmic. As in wild-type controls, FAA in Clk/Clk mutants persists after temporal feeding cues are removed for several cycles, indicating that the FEO is a circadian timer. This is the first demonstration that the Clock gene is not necessary for the expression of a circadian, food-entrained behavior and suggests that the FEO is mediated by a molecular mechanism distinct from that of the SCN.

scholarly journals Survival of photoreceptor neurons in the compound eye of Drosophila depends on connections with the optic ganglia

Development ◽  
1992 ◽  
Vol 114 (2) ◽  
pp. 355-366 ◽  
Author(s):  
A.R. Campos ◽  
K.F. Fischbach ◽  
H. Steller
Keyword(s):  
Trophic Interactions ◽  
Compound Eye ◽  
Normal Development ◽  
Optic Lobe ◽  
Photoreceptor Cells ◽  
Optic Lobes ◽  
Genetic Mosaic ◽  
Retinal Innervation ◽  
Photoreceptor Neurons ◽  
The Brain

The importance of retinal innervation for the normal development of the optic ganglia in Drosophila is well documented. However, little is known about retrograde effects of the optic lobe on the adult photoreceptor cells (R-cells). We addressed this question by examining the survival of R-cells in mutant flies where R-cells do not connect to the brain. Although imaginal R-cells develop normally in the absence of connections to the optic lobes, we find that their continued survival requires these connections. Genetic mosaic studies with the disconnected (disco) mutation demonstrate that survival of R-cells does not depend on the genotype of the eye, but is correlated with the presence of connections to the optic ganglia. These results suggest the existence of retrograde interactions in the Drosophila visual system reminiscent of trophic interactions found in vertebrates.

Computer Reconstruction of the Cellular Architecture of the Daphnia Magna Optic Ganglion

1975 ◽  
Vol 33 ◽  
pp. 284-285
Author(s):  
E. R. Macagno ◽  
C. Levinthal
Keyword(s):  
Daphnia Magna ◽  
Genetic Background ◽  
Compound Eye ◽  
Synaptic Connectivity ◽  
Serial Sections ◽  
Cross Sectional ◽  
Small Crustacean ◽  
Optic Ganglion ◽  
Structural Invariance ◽  
High Degree

The optic ganglion of Daphnia Magna, a small crustacean that reproduces parthenogenetically contains about three hundred neurons: 110 neurons in the Lamina or anterior region and about 190 neurons in the Medulla or posterior region. The ganglion lies in the midplane of the organism and shows a high degree of left-right symmetry in its structures. The Lamina neurons form the first projection of the visual output from 176 retinula cells in the compound eye. In order to answer questions about structural invariance under constant genetic background, we have begun to reconstruct in detail the morphology and synaptic connectivity of various neurons in this ganglion from electron micrographs of serial sections (1). The ganglion is sectioned in a dorso-ventra1 direction so as to minimize the cross-sectional area photographed in each section. This area is about 60 μm x 120 μm, and hence most of the ganglion fit in a single 70 mm micrograph at the lowest magnification (685x) available on our Zeiss EM9-S.

A View of the Lexical–Grammatical Link in Young Latinos With Specific Language Impairment Using Language-Specific and Conceptual Measures

2019 ◽  
Vol 62 (6) ◽  
pp. 1775-1786 ◽  
Author(s):  
Lucía I. Méndez ◽  
Gabriela Simon-Cereijido
Keyword(s):  
Low Income ◽  
Language Impairment ◽  
Specific Language Impairment ◽  
L2 Acquisition ◽  
Cross Sectional ◽  
Specific Language ◽  
Vocabulary Skills ◽  
In The Beginning ◽  
Study Participants ◽  
L1 And L2

Purpose This study investigated the nature of the association of lexical–grammatical abilities within and across languages in Latino dual language learners (DLLs) with specific language impairment (SLI) using language-specific and bilingual measures. Method Seventy-four Spanish/English–speaking preschoolers with SLI from preschools serving low-income households participated in the study. Participants had stronger skills in Spanish (first language [L1]) and were in the initial stages of learning English (second language [L2]). The children's lexical, semantic, and grammar abilities were assessed using normative and researcher-developed tools in English and Spanish. Hierarchical linear regressions of cross-sectional data were conducted using measures of sentence repetition tasks, language-specific vocabulary, and conceptual bilingual lexical and semantic abilities in Spanish and English. Results Results indicate that language-specific vocabulary abilities support the development of grammar in L1 and L2 in this population. L1 vocabulary also contributes to L2 grammar above and beyond the contribution of L2 vocabulary skills. However, the cross-linguistic association between vocabulary in L2 and grammar skills in the stronger or more proficient language (L1) is not observed. In addition, conceptual vocabulary significantly supported grammar in L2, whereas bilingual semantic skills supported L1 grammar. Conclusions Our findings reveal that the same language-specific vocabulary abilities drive grammar development in L1 and L2 in DLLs with SLI. In the early stages of L2 acquisition, vocabulary skills in L1 also seem to contribute to grammar skills in L2 in this population. Thus, it is critical to support vocabulary development in both L1 and L2 in DLLs with SLI, particularly in the beginning stages of L2 acquisition. Clinical and educational implications are discussed.

scholarly journals Understanding Quantitative Circadian Regulations Are Crucial Towards Advancing Chronotherapy

Cells ◽  
2019 ◽  
Vol 8 (8) ◽  
pp. 883 ◽  
Author(s):  
Debajyoti Chowdhury ◽  
Chao Wang ◽  
Ai-Ping Lu ◽  
Hai-Long Zhu
Keyword(s):  
Circadian Rhythms ◽  
Molecular Mechanisms ◽  
Temporal Stability ◽  
Biological Rhythms ◽  
Integrative Approach ◽  
Peripheral Tissues ◽  
Innovative Strategies ◽  
Neural Connections ◽  
Core Components ◽  
The Brain

Circadian rhythms have a deep impact on most aspects of physiology. In most organisms, especially mammals, the biological rhythms are maintained by the indigenous circadian clockwork around geophysical time (~24-h). These rhythms originate inside cells. Several core components are interconnected through transcriptional/translational feedback loops to generate molecular oscillations. They are tightly controlled over time. Also, they exert temporal controls over many fundamental physiological activities. This helps in coordinating the body’s internal time with the external environments. The mammalian circadian clockwork is composed of a hierarchy of oscillators, which play roles at molecular, cellular, and higher levels. The master oscillation has been found to be developed at the hypothalamic suprachiasmatic nucleus in the brain. It acts as the core pacemaker and drives the transmission of the oscillation signals. These signals are distributed across different peripheral tissues through humoral and neural connections. The synchronization among the master oscillator and tissue-specific oscillators offer overall temporal stability to mammals. Recent technological advancements help us to study the circadian rhythms at dynamic scale and systems level. Here, we outline the current understanding of circadian clockwork in terms of molecular mechanisms and interdisciplinary concepts. We have also focused on the importance of the integrative approach to decode several crucial intricacies. This review indicates the emergence of such a comprehensive approach. It will essentially accelerate the circadian research with more innovative strategies, such as developing evidence-based chronotherapeutics to restore de-synchronized circadian rhythms.

The acquisition of requests by second language learners of Spanish

2005 ◽  
Vol 2 (1) ◽  
pp. 1-27 ◽  
Author(s):  
Derrin Pinto
Keyword(s):  
Language Learning ◽  
Language Learners ◽  
Second Language Learners ◽  
Cross Sectional Study ◽  
Cross Sectional ◽  
Advanced Learners ◽  
English Speaking ◽  
Request Strategies ◽  
Using Data ◽  
L1 And L2

This cross-sectional study in interlanguage pragmatics analyzes the requests employed by English-speaking learners of L2 Spanish, using data collected from university students at four different levels of language learning. The most common request strategies are first identified in a cross-linguistic analysis of Spanish and English and are then compared to the interlanguage data. The requests of lower-level students are found to be more idiosyncratic and pragmatically ambiguous than those of advanced learners, although not necessarily more direct. Advanced learners show signs of improvement, but still rely largely on L1 request behavior. Learners at all levels display more difficulties in areas in which there is cross-linguistic variation between the L1 and L2.

Disrupted circadian rhythms in VIP- and PHI-deficient mice

2003 ◽  
Vol 285 (5) ◽  
pp. R939-R949 ◽  
Author(s):  
Christopher S. Colwell ◽  
Stephan Michel ◽  
Jason Itri ◽  
Williams Rodriguez ◽  
J. Tam ◽  
...  
Keyword(s):  
Circadian Rhythms ◽  
Wheel Running ◽  
Activity Rhythm ◽  
Activity Patterns ◽  
Circadian System ◽  
Diurnal Rhythms ◽  
Constant Darkness ◽  
Light Cycle ◽  
Wild Type ◽  
Deficient Mice

The related neuropeptides vasoactive intestinal peptide (VIP) and peptide histidine isoleucine (PHI) are expressed at high levels in the neurons of the suprachiasmatic nucleus (SCN), but their function in the regulation of circadian rhythms is unknown. To study the role of these peptides on the circadian system in vivo, a new mouse model was developed in which both VIP and PHI genes were disrupted by homologous recombination. In a light-dark cycle, these mice exhibited diurnal rhythms in activity which were largely indistinguishable from wild-type controls. In constant darkness, the VIP/PHI-deficient mice exhibited pronounced abnormalities in their circadian system. The activity patterns started ∼8 h earlier than predicted by the previous light cycle. In addition, lack of VIP/PHI led to a shortened free-running period and a loss of the coherence and precision of the circadian locomotor activity rhythm. In about one-quarter of VIP/PHI mice examined, the wheel-running rhythm became arrhythmic after several weeks in constant darkness. Another striking example of these deficits is seen in the split-activity patterns expressed by the mutant mice when they were exposed to a skeleton photoperiod. In addition, the VIP/PHI-deficient mice exhibited deficits in the response of their circadian system to light. Electrophysiological analysis indicates that VIP enhances inhibitory synaptic transmission within the SCN of wild-type and VIP/PHI-deficient mice. Together, the observations suggest that VIP/PHI peptides are critically involved in both the generation of circadian oscillations as well as the normal synchronization of these rhythms to light.

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