Cell size homeostasis under the circadian regulation of cell division in cyanobacteria

Bacterial cells maintain their characteristic cell size over many generations. Several rod-shaped bacteria, such as Escherichia coli and the cyanobacteria Synechococcus elongatus, divide after adding a constant length to their length at birth. Through this division control known as the adder mechanism, perturbation in cell length due to physiological fluctuation decays over generations at a rate of 2^-1 per cell division. However, previous experiments have shown that the circadian clock in cyanobacteria reduces cell division frequency at a specific time of day under constant light. This circadian gating should modulate the division control by the adder mechanism, but its significance remains unknown. Here we address how the circadian gating affects cell length, doubling time, and cell length stability in cyanobacteria by using mathematical models. We show that a cell subject to circadian gating grows for a long time, and gives birth to elongated daughter cells. These elongated daughter cells grow faster than the previous generation, as elongation speed is proportional to cell length and divide in a short time before the next gating. Hence, the distributions of doubling time and cell length become bimodal, as observed in experimental data. Interestingly, the average doubling time over the population of cells is independent of gating because the extension of doubling time by gating is compensated by its reduction in the subsequent generation. On the other hand, average cell length is increased by gating, suggesting that the circadian clock controls cell length. We then show that the decay rate of perturbation in cell length depends on the ratio of delay in division by the gating τ_G to the average doubling time τ₀ as [Formula: see text] . We estimated τ_G≈2.5, τ₀≈13.6 hours, and τ_G/τ₀≈0.18 from experimental data, indicating that a long doubling time in cyanobacteria maintains the decay rate similar to that of the adder mechanism. Thus, our analysis suggests that the acquisition of the circadian clock during evolution did not impose a constraint on cell size homeostasis in cyanobacteria.

Nanoscale-tipped wire array injections transfer DNA directly into brain cells ex vivo and in vivo

Genetic modification to restore cell functions in the brain can be performed through the delivery of biomolecules in a minimally invasive manner into live neuronal cells within brain tissues. However, conventional nanoscale needles are too short (lengths of ~10 µm) to target neuronal cells in ~1‐mm‐thick brain tissues because the neuronal cells are located deep within the tissue. Here, we report the use of nanoscale‐tipped wire (NTW) arrays with diameters < 100 nm and wire lengths of ~200 µm to address biomolecule delivery issues. The NTW arrays were manufactured by growth of silicon microwire arrays and nanotip formation. This technique uses pinpoint, multiple‐cell DNA injections in deep areas of brain tissues, enabling target cells to be marked by fluorescent protein (FP) expression vectors. This technique has potential for use for electrophysiological recordings and biological transfection into neuronal cells. Herein, simply pressing an NTW array delivers and expresses plasmid DNA in multiple‐cultured cells and multiple‐neuronal cells within a brain slice with reduced cell damage. Additionally, DNA transfection is demonstrated using brain cells ex vivo and in vivo. Moreover, knockdown of a critical clock gene after injecting a short hairpin RNA (shRNA) and a genome‐editing vector demonstrates the potential to genetically alter the function of living brain cells, for example, pacemaker cells of the mammalian circadian rhythms. Overall, our NTW array injection technique enables genetic and functional modification of living cells in deep brain tissue areas, both ex vivo and in vivo.

Complementary phase responses via functional differentiation of dual negative feedback loops

Multiple feedback loops are often found in gene regulations for various cellular functions. In mammalian circadian clocks, oscillations of Period1 (Per1) and Period2 (Per2) expression are caused by interacting negative feedback loops (NFLs) whose protein products with similar molecular functions repress each other. However, Per1 expression peaks earlier than Per2 in the pacemaker tissue, raising the question of whether the peak time difference reflects their different dynamical functions. Here, we address this question by analyzing phase responses of the circadian clock caused by light-induced transcription of both Per1 and Per2 mRNAs. Through mathematical analyses of dual NFLs, we show that phase advance is mainly driven by light inputs to the repressor with an earlier expression peak as Per1, whereas phase delay is driven by the other repressor with a later peak as Per2. Due to the complementary contributions to phase responses, the ratio of light-induced transcription rates between Per1 and Per2 determines the magnitude and direction of phase shifts at each time of day. Specifically, stronger Per1 light induction than Per2 results in a phase response curve (PRC) with a larger phase advance zone than delay zone as observed in rats and hamsters, whereas stronger Per2 induction causes a larger delay zone as observed in mice. Furthermore, the ratio of light-induced transcription rates required for entrainment is determined by the relation between the circadian and light-dark periods. Namely, if the autonomous period of a circadian clock is longer than the light-dark period, a larger light-induced transcription rate of Per1 than Per2 is required for entrainment, and vice versa. In short, the time difference between Per1 and Per2 expression peaks can differentiate their dynamical functions. The resultant complementary contributions to phase responses can determine entrainability of the circadian clock to the light-dark cycle.

Co-precipitation molecules hemopexin and transferrin may be key molecules for fibrillogenesis in TTR V30M amyloidogenesis

The disease model of familial amyloidotic polyneuropathy—7.2-hMet30 mice—manifests amyloid deposition that consists of a human amyloidogenic mutant transthyretin (TTR) (TTR V30M). Our previous study found amyloid deposits in 14 of 27 7.2-hMet30 mice at 21–24 months of age. In addition, non-fibrillar TTR deposits were found in amyloid-negative 7.2hMet30 mice. These results suggested that TTR amyloidogenesis required not only mutant TTR but also an additional factor (or factors) as an etiologic molecule. To determine the differences in serum proteome in amyloid-positive and amyloid-negative mice in the 7.2-hMet30 model, we used proteomic analyses and studied serum samples obtained from these mice. Hemopexin (HPX) and transferrin (Tf) were detected in the serum samples from amyloid-positive mice and were also found in amyloid deposits via immunohistochemistry, but serum samples from amyloid-negative mice did not contain HPX and Tf. These two proteins were also not detected in non-fibrillar TTR deposits. In addition, in silico analyses suggested that HPX and Tf facilitate destabilization of TTR secondary structures and misfolding of TTR. These results suggest that HPX and Tf may be associated with TTR amyloidogenesis after fibrillogenesis in vivo.

Bone Resorption Is Regulated by Circadian Clock in Osteoblasts

We have previously shown that endochondral ossification is finely regulated by the Clock system expressed in chondrocytes during postnatal skeletogenesis. Here we show a sophisticated modulation of bone resorption and bone mass by the Clock system through its expression in bone-forming osteoblasts. Brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein 1 (Bmal1) and Period1 (Per1) were expressed with oscillatory rhythmicity in the bone in vivo, and circadian rhythm was also observed in cultured osteoblasts of Per1::luciferase transgenic mice. Global deletion of murine Bmal1, a core component of the Clock system, led to a low bone mass, associated with increased bone resorption. This phenotype was recapitulated by the deletion of Bmal1 in osteoblasts alone. Co-culture experiments revealed that Bmal1-deficient osteoblasts have a higher ability to support osteoclastogenesis. Moreover, 1α,25-dihydroxyvitamin D3 [1,25(OH)2 D3 ]-induced receptor activator of nuclear factor κB ligand (Rankl) expression was more strongly enhanced in both Bmal1-deficient bone and cultured osteoblasts, whereas overexpression of Bmal1/Clock conversely inhibited it in osteoblasts. These results suggest that bone resorption and bone mass are regulated at a sophisticated level by osteoblastic Clock system through a mechanism relevant to the modulation of 1,25(OH)2 D3 -induced Rankl expression in osteoblasts. © 2017 American Society for Bone and Mineral Research.

RNAi-mediated knockdown of mouse melanocortin-4 receptor in vitro and in vivo, using an siRNA expression construct based on the mir-187 precursor

RNA interference (RNAi) is a powerful tool for the study of gene function in mammalian systems, including transgenic mice. Here, we report a gene knockdown system based on the human mir-187 precursor. We introduced small interfering RNA (siRNA) sequences against the mouse melanocortin-4 receptor (mMc4r) to alter the targeting of miR-187. The siRNA-expressing cassette was placed under the control of the cytomegalovirus (CMV) early enhancer/chicken β-actin promoter. In vitro, the construct efficiently knocked down the gene expression of a co-transfected mMc4r-expression vector in cultured mammalian cells. Using this construct, we generated a transgenic mouse line which exhibited partial but significant knockdown of mMc4r mRNA in various brain regions. Northern blot analysis detected transgenic expression of mMc4r siRNA in these regions. Furthermore, the transgenic mice fed a normal diet ate 9% more and were 30% heavier than wild-type sibs. They also developed hyperinsulinemia and fatty liver as do mMc4r knockout mice. We determined that this siRNA expression construct based on mir-187 is a practical and useful tool for gene functional studies in vitro as well as in vivo.

The intrinsic microglial clock system regulates interleukin-6 expression

Similar to neurons, microglia have an intrinsic molecular clock. The master clock oscillator Bmal1 modulates interleukin-6 upregulation in microglial cells exposed to lipopolysaccharide. Bmal1 can play a role in microglial inflammatory responses. We previously demonstrated that gliotransmitter ATP induces transient expression of the clock gene Period1 via P2X7 purinergic receptors in cultured microglia. In this study, we further investigated mechanisms underlying the regulation of pro-inflammatory cytokine production by clock molecules in microglial cells. Several clock gene transcripts exhibited oscillatory diurnal rhythmicity in microglial BV-2 cells. Real-time luciferase monitoring also showed diurnal oscillatory luciferase activity in cultured microglia from Per1::Luciferase transgenic mice. Lipopolysaccharide (LPS) strongly induced the expression of pro-inflammatory cytokines in BV-2 cells, whereas an siRNA targeting Brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein 1 (Bmal1), a core positive component of the microglial molecular clock, selectively inhibited LPS-induced interleukin-6 (IL-6) expression. In addition, LPS-induced IL-6 expression was attenuated in microglia from Bmal1-deficient mice. This phenotype was recapitulated by pharmacological disruption of oscillatory diurnal rhythmicity using the synthetic Rev-Erb agonist SR9011. Promoter analysis of the Il6 gene revealed that Bmal1 is required for LPS-induced IL-6 expression in microglia. Mice conditionally Bmal1 deficient in cells expressing CD11b, including microglia, exhibited less potent upregulation of Il6 expression following middle cerebral artery occlusion compared with that in control mice, with a significant attenuation of neuronal damage. These results suggest that the intrinsic microglial clock modulates the inflammatory response, including the positive regulation of IL-6 expression in a particular pathological situation in the brain, GLIA 2016. GLIA 2017;65:198-208.

In vivo bioluminescence and reflectance imaging of multiple organs in bioluminescence reporter mice by bundled-fiber-coupled microscopy

Bioluminescence imaging (BLI) is used in biomedical research to monitor biological processes within living organisms. Recently, fiber bundles with high transmittance and density have been developed to detect low light with high resolution. Therefore, we have developed a bundled-fiber-coupled microscope with a highly sensitive cooled-CCD camera that enables the BLI of organs within the mouse body. This is the first report of in vivo BLI of the brain and multiple organs in luciferase-reporter mice using bundled-fiber optics. With reflectance imaging, the structures of blood vessels and organs can be seen clearly with light illumination, and it allowed identification of the structural details of bioluminescence images. This technique can also be applied to clinical diagnostics in a low invasive manner.

Real-Time Recording of Circadian Per1 and Per2 Expression in the Suprachiasmatic Nucleus of Freely Moving Rats

Measuring real-time gene activity in the brains of freely moving animals presents a challenging issue in neuroscience research. Circadian gene expression in neurons of the suprachiasmatic nucleus (SCN), a small nucleus in the hypothalamus, is reflected in behavioral rhythmicity. Cellular oscillatory gene expression is generated by a transcription-translation feedback loop of clock genes including 2 oscillatory genes, Per1 and Per2. Here we have succeeded in real-time monitoring of Per1 and Per2 transcription separately by detecting the bioluminescence of luciferase (luc) reporters using a plastic optical fiber inserted into the SCN of freely moving rats. Per1-luc and Per2-luc rhythms peaked in the middle and late subjective day, respectively, which was confirmed by quantitative PCR-based measurements of SCN tissue samples. Studies of in vivo transcriptional states of clock genes in freely moving animals should improve our understanding of how clock gene expression is reflected in behavior.

Molecular assembly of the period-cryptochrome circadian transcriptional repressor complex

The mammalian circadian clock is driven by a transcriptional-translational feedback loop, which produces robust 24-hr rhythms. Proper oscillation of the clock depends on the complex formation and periodic turnover of the Period and Cryptochrome proteins, which together inhibit their own transcriptional activator complex, CLOCK-BMAL1. We determined the crystal structure of the CRY-binding domain (CBD) of PER2 in complex with CRY2 at 2.8 Å resolution. PER2-CBD adopts a highly extended conformation, embracing CRY2 with a sinuous binding mode. Its N-terminal end tucks into CRY adjacent to a large pocket critical for CLOCK-BMAL1 binding, while its C-terminal half flanks the CRY2 C-terminal helix and sterically hinders the recognition of CRY2 by the FBXL3 ubiquitin ligase. Unexpectedly, a strictly conserved intermolecular zinc finger, whose integrity is important for clock rhythmicity, further stabilizes the complex. Our structure-guided analyses show that these interspersed CRY-interacting regions represent multiple functional modules of PERs at the CRY-binding interface.

Positive autoregulation delays the expression phase of mammalian clock gene Per2

In mammals, cellular circadian rhythms are generated by a transcriptional-translational autoregulatory network that consists of clock genes that encode transcriptional regulators. Of these clock genes, Period1 (Per1) and Period2 (Per2) are essential for sustainable circadian rhythmicity and photic entrainment. Intriguingly, Per1 and Per2 mRNAs exhibit circadian oscillations with a 4-hour phase difference, but they are similarly transactivated by CLOCK-BMAL1. In this study, we investigated the mechanism underlying the phase difference between Per1 and Per2 through a combination of mathematical simulations and molecular experiments. Mathematical analyses of a model for the mammalian circadian oscillator demonstrated that the slow synthesis and fast degradation of mRNA tend to advance the oscillation phase of mRNA expression. However, the phase difference between Per1 and Per2 was not reproduced by the model, which implemented a 1.1-fold difference in degradation rates and a 3-fold difference in CLOCK-BMAL1 mediated inductions of Per1 and Per2 as estimated in cultured mammalian cells. Thus, we hypothesized the existence of a novel transcriptional activation of Per2 by PER1/2 such that the Per2 oscillation phase was delayed. Indeed, only the Per2 promoter, but not Per1, was strongly induced by both PER1 and PER2 in the presence of CLOCK-BMAL1 in a luciferase reporter assay. Moreover, a 3-hour advance was observed in the transcriptional oscillation of the delta-Per2 reporter gene lacking cis-elements required for the induction by PER1/2. These results indicate that the Per2 positive feedback regulation is a significant factor responsible for generating the phase difference between Per1 and Per2 gene expression.

Period-phase map: two-dimensional selection of circadian rhythm-related genes

Many genes related to the circadian rhythm, especially those involved in phase shifts induced by different environmental stimuli, still remain enigmatic. In this study, the authors monitored the expression of rat genes measured with multiple phase-resetting stimuli, and developed a technique to extract the candidate genes for the changes in circadian rhythm by the stimuli, from microarray data. First, the spectra for the time series of gene expression were estimated by fast Fourier transform, and then two fitting methods, the random period fitting method and the conditional curve fitting method, using the estimated periods as the initial values, were applied to the control and the stimulated expression data to estimate the periods and the phases. Finally, by comparing the two sets of periods and phases, the period change and the phase shift by stimuli were estimated to extract the candidate genes related to the master clock, by mapping the period change and the phase shift on a two-dimensional space, a period-phase map (PPM). As an indirect validation of the genes selected by our method, the significant enrichment of extracted gene clusters on the PPM was further evaluated, in terms of biological function. As a result, the gene clusters related to photoreceptors and neural regulation emerged on the PPM, thus implying the relationships in the stimulus response of the master clock that resides in the brain at the intersection of the optic nerves. Thus, the present approach is a feasible means to explore the oscillatory genes related to stimulus responses.

Ontogeny of circadian organization in the rat

The mammalian circadian system is orchestrated by a master pacemaker in the brain, but many peripheral tissues also contain independent or quasi-independent circadian oscillators. The adaptive significance of clocks in these structures must lie, in large part, in the phase relationships between the constituent oscillators and their micro- and macroenvironments. To examine the relationship between postnatal development, which is dependent on endogenous programs and maternal/environmental influences, and the phase of circadian oscillators, the authors assessed the circadian phase of pineal, liver, lung, adrenal, and thyroid tissues cultured from Period 1-luciferase (Per1-luc ) rat pups of various postnatal ages. The liver, thyroid, and pineal were rhythmic at birth, but the phases of their Per1-luc expression rhythms shifted remarkably during development. To determine if the timing of the phase shift in each tissue could be the result of changing environmental conditions, the behavior of pups and their mothers was monitored. The circadian phase of the liver shifted from the day to night around postnatal day (P) 22 as the pups nursed less during the light and instead ate solid food during the dark. Furthermore, the phase of Per1-luc expression in liver cultures from nursing neonates could be shifted experimentally from the day to the night by allowing pups access to the dam only during the dark. Peak Per1-luc expression also shifted from midday to early night in thyroid cultures at about P20, concurrent with the shift in eating times. The phase of Per1-luc expression in the pineal gland shifted from day to night coincident with its sympathetic innervation at around P5. Per1-luc expression was rhythmic in adrenal cultures and peaked around the time of lights-off throughout development; however, the amplitude of the rhythm increased at P25. Lung cultures were completely arrhythmic until P12 when the pups began to leave the nest. Taken together, the data suggest that the molecular machinery that generates circadian oscillations matures at different rates in different tissues and that the phase of at least some peripheral organs is malleable and may shift as the organ's function changes during development.

Genetic and molecular analysis of wild-derived arrhythmic mice

A new circadian variant was isolated by screening the intercross offspring of wild-caught mice (Mus musculus castaneus). This variant was characterized by an initial maintenance of damped oscillations and subsequent loss of rhythmicity after being transferred from light-dark (LD) cycles to constant darkness (DD). To map the genes responsible for the persistence of rhythmicity (circadian ratio) and the length of free-running period (tau), quantitative trait locus (QTL) analysis was performed using F(2) mice obtained from an F(1) cross between the circadian variant and C57BL/6J mice. As a result, a significant QTL with a main effect for circadian ratio (Arrhythmicity; Arrh-1) was mapped on Chromosome (Chr) 8. For tau, four significant QTLs, Short free-running period (Sfp-1) (Chr 1), Sfp-2 (Chr 6), Sfp-3 (Chr 8), Sfp-4 (Chr 11) were determined. An epistatic interaction was detected between Chr 3 (Arrh-2) and Chr 5 (Arrh-3). An in situ hybridization study of clock genes and mouse Period1::luciferase (mPer1::luc) real-time monitoring analysis in the suprachiasmatic nucleus (SCN) suggested that arrhythmicity in this variant might not be attributed to core circadian mechanisms in the SCN neurons. Our strategy using wild-derived variant mice may provide a novel opportunity to evaluate circadian and its related disorders in human that arise from the interaction between multiple variant genes.

Maternal feeding controls fetal biological clock

Background

It is widely accepted that circadian physiological rhythms of the fetus are affected by oscillators in the maternal brain that are coupled to the environmental light-dark (LD) cycle.

Methodology/Principal Findings

To study the link between fetal and maternal biological clocks, we investigated the effects of cycles of maternal food availability on the rhythms of Per1 gene expression in the fetal suprachiasmatic nucleus (SCN) and liver using a transgenic rat model whose tissues express luciferase in vitro. Although the maternal SCN remained phase-locked to the LD cycle, maternal restricted feeding phase-advanced the fetal SCN and liver by 5 and 7 hours respectively within the 22-day pregnancy.

Conclusions/Significance

Our results demonstrate that maternal feeding entrains the fetal SCN and liver independently of both the maternal SCN and the LD cycle. This indicates that maternal-feeding signals can be more influential for the fetal SCN and particular organ oscillators than hormonal signals controlled by the maternal SCN, suggesting the importance of a regular maternal feeding schedule for appropriate fetal molecular clockwork during pregnancy.

Reorganization of the suprachiasmatic nucleus coding for day length

In mammals, the suprachiasmatic nucleus (SCN), the circadian pacemaker, receives light information via the retina and functions in the entrainment of circadian rhythms and in phasing the seasonal responses of behavioral and physiological functions. To better understand photoperiod-related alterations in the SCN physiology, we analyzed the clock gene expression in the mouse SCN by performing in situ hybridization and real-time monitoring of the mPer1::luc bioluminescence. Under long photoperiod (LP) conditions, the expression rhythms of mPer1 and Bmal1 in the caudal SCN phase-led those in the rostral SCN; further, within the middle SCN, the rhythms in the ventrolateral (VL)-like subdivision advanced compared with those in the dorsomedial (DM)-like subdivision. The mPer1::luc rhythms in the entire coronal slice obtained from the middle SCN exhibited 2 peaks with a wide peak width under LP conditions. Imaging analysis of the mPer1::luc rhythms in several subdivisions of the rostral, middle, caudal, and horizontal SCN revealed wide regional variations in the peak time in the rostral half of the SCN under LP conditions. These variations were not due to alterations in the waveform of a single SCN neuronal rhythm. Our results indicate that LP conditions induce phase changes in the rhythms in multiple regions in the rostral half of the SCN; this leads to different circadian waveforms in the entire SCN, coding for day length.

Bimodal clock gene expression in mouse suprachiasmatic nucleus and peripheral tissues under a 7-hour light and 5-hour dark schedule

Using the mPer1::luc real-time monitoring technique, the authors observed the bimodal patterns of mPer1 bioluminescence on each side of the SCN, in parallel with maintaining synchronization between the left and right sides of the SCN under an artificial light:dark:light:dark (LDLD) 7:5:7:5 condition. In situ hybridization analysis of mPer1 and mBmal1 mRNA distribution in the SCN showed that in 1 photophase (morning photophase; M) of LDLD, the mPer1 level in the ventrolateral-like (VL-like) subdivision of the SCN was higher than that in the dorsomedial-like (DM-like) subdivision, and this regional distribution pattern was reversed in another photophase (evening photophase; E). In contrast, the mBmal1 level was higher in the DM-like subdivision than in the VL-like subdivision in the M phase, and this distribution changed in the E phase. The prokineticin 2 (PK2) mRNA that encodes an SCN output molecule that is thought to transmit the circadian locomotor rhythms was reduced in both the DM-like and VL-like SCN and did not clearly correlate with the activity under the LDLD condition. The expression of mPer1 and mPer2 in the liver was clearly bimodal, whereas the expressions of other clock genes were not synchronized to the LDLD condition. These results may provide important insights into the mechanism underlying the splitting or bimodal rhythms that may in turn facilitate the understanding of the ability to measure the seasonal day length in mammals.

Clinical-diffusion mismatch defined by NIHSS and ASPECTS in non-lacunar anterior circulation infarction

OBJECTIVES

Instead of the mismatch in MRI between the perfusion-weighted imaging (PWI) lesion and the smaller diffusion-weighted imaging (DWI) lesion (PWI-DWI mismatch), clinical-DWI mismatch (CDM) has been proposed as a new diagnostic marker of brain tissue at risk of infarction in acute ischemic stroke. The Alberta Stroke Program Early CT Score (ASPECTS) has recently been applied to detect early ischemic change of acute ischemic stroke. The present study applies the CDM concept to DWI data and investigated the utility of the CDM defined by the NIH Stroke Scale (NIHSS) and ASPECTS in patients with non-lacunar anterior circulation infarction.

METHODS

Eighty-seven patients with first ever ischemic stroke within 24 hours of onset with symptoms of non-lacunar anterior circulation infarction with the NIHSS score>or=8 were enrolled. Initial lesion extent was measured by the ASPECTS on DWI within 24 hours, and initial neurological score was measured by the NIHSS. As NIHSS>or=8 has been suggested as a clinical indicator of a large volume of ischemic brain tissue, and the majority of patients with non-lacunar anterior infarction with score of NIHSS<8 had lesions with ASPECTS>or=8 on DWI, so CDM was defined as NIHSS>or=8 and DWI-ASPECTS 8>or=. We divided patients into matched and mismatched patient groups, and compared them with respect to background characteristics, neurological findings, laboratory data, radiological findings and outcome.

RESULTS

There were 35 CDM-positive patients (P group, 40.2%) and 52 CDM-negative patients (N group , 59.8%). P group patients had a higher risk of early neurological deterioration (END) than N group patients (37.1% vs 13.5%, p<0.05), which were always accompanied by lesion growth defined by 2 or more points decrease on ASPECTS (36 to 72 hours after onset on CT). The NIHSS at entry were significantly lower in the P group, but there was no difference in the outcome at three months measured by the modified Rankin Scale. However, CDM was not an independent predictor of END by multiple logistic regression analysis.

CONCLUSIONS

Patients with CDM had high rate of early neurological deterioration and lesion growth. CDM defined as NIHSS>or=8 and DWI-ASPECTS>or=8 can be another marker for detecting patients with tissue at risk of infarction, but more work is needed to clarify whether this CDM method is useful in acute stroke management.

Establishment of cell lines derived from the rat suprachiasmatic nucleus

Physiological and behavioral circadian rhythms in mammals are orchestrated by a central circadian clock located in the suprachiasmatic nucleus (SCN) of the hypothalamus. Photic input entrains the phase of the central clock, and many peripheral clocks are regulated by neural or hormonal output from the SCN. We established cell lines derived from the rat embryonic SCN to examine the molecular network of the central clock. An established cell line exhibited the stable circadian expression of clock genes. The circadian oscillation was abruptly phase-shifted by forskolin, and abolished by siBmal1. These results are compatible with in vivo studies of the SCN.

LARK activates posttranscriptional expression of an essential mammalian clock protein, PERIOD1

The mammalian molecular clock is composed of feedback loops to keep circadian 24-h rhythms. Although much focus has been on transcriptional regulation, it is clear that posttranscriptional controls also play important roles in molecular circadian clocks. In this study, we found that mouse LARK (mLARK), an RNA binding protein, activates the posttranscriptional expression of the mouse Period1 (mPer1) mRNA. A strong circadian cycling of the mLARK protein is observed in the suprachiasmatic nuclei with a phase similar to that of mPER1, although the level of the Lark transcripts are not rhythmic. We demonstrate that LARK causes increased mPER1 protein levels, most likely through translational regulation and that the LARK1 protein binds directly to a cis element in the 3' UTR of the mPer1 mRNA. Alterations of mLark expression in cycling cells caused significant changes in circadian period, with mLark knockdown by siRNA resulting in a shorter circadian period, and the overexpression of mLARK1 resulting in a lengthened period. These data indicate that mLARKs are novel posttranscriptional regulators of mammalian circadian clocks.

Predictors of good prognosis in total anterior circulation infarction within 6 h after onset under conventional therapy

OBJECTIVE

We investigated the predictors of good prognosis in total anterior circulation infarction (TACI), under conventional therapy.

METHODS

We enrolled 166 patients with first-ever ischemic stroke within 6 h after onset with symptoms of TACI. Sixty-three patients (38.0%) with good outcome [G group, the modified Rankin Disability Scale (mRS) after 3 months < or =3] and 103 patients (62.0%) with bad outcome (B group, mRS >3) were compared.

RESULTS

On univariate analysis, G group patients were significantly younger, had lower score in the National Institutes of Health Stroke Scale (NIHSS) of total and consciousness sub-score, had lower rate of clinical deterioration. On cranial CT at entry, three early CT signs [hyperdense middle cerebral artery (MCA) sign, hypodensity of >1/3 MCA and brain swelling] were significantly more frequent in the B group. On the second CT at 24-48 h, infarct area as assessed by the Alberta Stroke Programme Early CT Score (ASPECTS) was significantly smaller in the G group. Multivariate analysis with logistic regression revealed age <7 0 years, NIHSS < or =15, no clinical deterioration, and only no brain swelling in early CT signs, and ASPECTS > or =7 as independent predictors of good prognosis.

CONCLUSIONS

Some clinical variables are useful in predicting outcome in TACI within the early period after stroke onset.

A calcium flux is required for circadian rhythm generation in mammalian pacemaker neurons

Generation of mammalian circadian rhythms involves molecular transcriptional and translational feedback loops. It is not clear how membrane events interact with the intracellular molecular clock or whether membrane activities are involved in the actual generation of the circadian rhythm. We examined the role of membrane potential and calcium (Ca2+) influx in the expression of the circadian rhythm of the clock gene Period 1 (Per1) within the rat suprachiasmatic nucleus (SCN), the master pacemaker controlling circadian rhythmicity. Membrane hyperpolarization, caused by lowering the extracellular concentration of potassium or blocking Ca2+ influx in SCN cultures by lowering [Ca2+], reversibly abolished the rhythmic expression of Per1. In addition, the amplitude of Per1 expression was markedly decreased by voltage-gated Ca2+ channel antagonists. A similar result was observed for mouse Per1 and PER2. Together, these results strongly suggest that a transmembrane Ca2+ flux is necessary for sustained molecular rhythmicity in the SCN. We propose that periodic Ca2+ influx, resulting from circadian variations in membrane potential, is a critical process for circadian pacemaker function.

Constitutive expression of the Period1 gene impairs behavioral and molecular circadian rhythms

Three mammalian Period (Per) genes, termed Per1, Per2, and Per3, have been identified as structural homologues of the Drosophila circadian clock gene, period (per). The three Per genes are rhythmically expressed in the suprachiasmatic nucleus (SCN), the central circadian pacemaker in mammals. The phases of peak mRNA levels for the three Per genes in the SCN are slightly different. Light sequentially induces the transcripts of Per1 and Per2 but not of Per3 in mice. These data and others suggest that each Per gene has a different but partially redundant function in mammals. To elucidate the function of Per1 in the circadian system in vivo, we generated two transgenic rat lines in which the mouse Per1 (mPer1) transcript was constitutively expressed under the control of either the human elongation factor-1alpha (EF-1alpha) or the rat neuron-specific enolase (NSE) promoter. The transgenic rats exhibited an approximately 0.6-1.0-h longer circadian period than their wild-type siblings in both activity and body temperature rhythms. Entrainment in response to light cycles was dramatically impaired in the transgenic rats. Molecular analysis revealed that the amplitudes of oscillation in the rat Per1 (rPer1) and rat Per2 (rPer2) mRNAs were significantly attenuated in the SCN and eyes of the transgenic rats. These results indicate that either the level of Per1, which is raised by overexpression, or its rhythmic expression, which is damped or abolished in over expressing animals, is critical for normal entrainment of behavior and molecular oscillation of other clock genes.

Plasticity of circadian behavior and the suprachiasmatic nucleus following exposure to non-24-hour light cycles

Period aftereffects are a form of behavioral plasticity in which the free-running period of circadian behavior undergoes experience-dependent changes. It is unclear whether this plasticity is age dependent and whether the changes in behavioral period relate to changes in the SCN or the retina, 2 known circadian pacemakers in mammals. To determine whether these changes vary with age, Per1-luc transgenic mice (in which the luciferase gene is driven by the Period1 promoter) of different ages were exposed to short (10 h light: 10 h dark, T20) or long (14 h light: 14 h dark, T28) light cycles (T cycles). Recordings of running-wheel activity in constant darkness (DD) revealed that the intrinsic periods of T20 mice were significantly shorter than of T28 mice at all ages. Aftereffects following the shorter light cycle were significantly smaller in mice older than 3 months, corresponding with a decreased ability to entrain to T20. Age did not diminish entrainment or aftereffects in the 28-h light schedule. The behavioral period of pups born in DD depended on the T cycle experienced in utero, showing maternal transference of aftereffects. Recordings of Per1-luc activity from the isolated SCN in vitro revealed that the SCN of young mice expressed aftereffects, but the periods of behavior and SCN were negatively correlated. Enucleation in DD had no effect on behavioral aftereffects, indicating the eyes are not required for aftereffects expression. These data show that circadian aftereffects are an age-dependent form of plasticity mediated by stable changes in the SCN and, importantly, extra-SCN tissues.

Temporal precision in the mammalian circadian system: a reliable clock from less reliable neurons

The mammalian SCN contains a biological clock that drives remarkably precise circadian rhythms in vivo and in vitro. This study asks whether the cycle-to-cycle variability of behavioral rhythms in mice can be attributed to precision of individual circadian pacemakers within the SCN or their interactions. The authors measured the standard deviation of the cycle-to-cycle period from 7-day recordings of running wheel activity, Period1 gene expression in cultured SCN explants, and firing rate patterns of dispersed SCN neurons. Period variability of the intact tissue and animal was lower than single neurons. The median variability of running wheel and Period1 rhythms was less than 40 min per cycle compared to 2.1 h in firing rate rhythms of dispersed SCN neurons. The most precise SCN neuron, with a period deviation of 1.1 h, was 10 times noisier than the most accurate SCN explant (0.1 h) or mouse (0.1 h) but comparable to the least stable explant (2.1 h) and mouse (1.1 h). This variability correlated with intrinsic period in mice and SCN explants but not with single cells. Precision was unrelated to the amplitude of rhythms and did not change significantly with age up to 1 year after birth. Analysis of the serial correlation of cycle-to-cycle period revealed that approximately half of this variability is attributable to noise outside the pacemaker. These results indicate that cell-cell interactions within the SCN reduce pacemaker noise to determine the precision of circadian rhythms in the tissue and in behavior.

Structural and functional analysis of 3' untranslated region of mouse Period1 mRNA

In order to investigate the post-transcriptional regulation of Period1 (Per1), the 3(')-untranslated region (3(')UTR) of mouse Per1 (mPer1) mRNA was characterized. In addition to high similarity between human and mouse Per1 3(')UTRs, AU-rich element and differentiation control element were found in both species. Transient transfection assays using LUC::mPer1 3(')UTR fusion genes revealed that the mPer1 3(')UTR repressed its own expression in a post-transcriptional manner. The region critical for this translational down-regulation was confined to nucleotide positions 322-517. These results suggest that the mPer1 3(')UTR could be involved in the generation of time lag between the transcriptional and translational products of mPer1 in the suprachiasmatic nucleus.

Bulla gouldiana period exhibits unique regulation at the mRNA and protein levels

The authors cloned the period (per) gene from the marine mollusk Bulla gouldiana, a well-characterized circadian model system. This allowed them to examine the characteristics of the per gene in a new phylum, and to make comparisons with the conserved PER domains previously characterized in insects and vertebrates. Only one copy of the per gene is present in the Bulla genome, and it is most similar to PER in two insects: the cockroach, Periplaneta americana, and silkmoth, Antheraea pernyi. Comparison with Drosophila PER (dPER) and murine PER 1 (mPER1) sequence reveals that there is greater sequence homology between Bulla PER (bPER) and dPER in the regions of dPER shown to be important to heterodimerization between dPER and Drosophila timeless. Although the structure suggests conservation between dPER and bPER, expression patterns differ. In all cells and tissues examined that are peripheral to the clock neurons in Bulla, bPer mRNA and protein are expressed constitutively in light:dark (LD) cycles. In the identified clock neurons, the basal retinal neurons (BRNs), a rhythm in bPer expression could be detected in LD cycles with a peak at zeitgeber time (ZT) 5 and trough expression at ZT 13. This temporal profile of expression more closely resembles that of mPER1 than that of dPER. bPer rhythms in the BRNs were not detected in continuous darkness. These analyses suggest that clock genes may be uniquely regulated in different circadian systems, but lead to similar control of rhythms at the cellular, tissue, and organismal levels.

Effects of aging on central and peripheral mammalian clocks

Circadian organization changes with age, but we do not know the extent to which age-related changes are the result of alterations in the central pacemakers, the peripheral oscillators, or the coupling mechanisms that hold the system together. By using transgenic rats with a luciferase (luc) reporter, we assessed the effects of aging on the rhythm of expression of the Period 1 (Per1) gene in the suprachiasmatic nucleus (SCN) and in peripheral tissues. Young (2 months) and aged (24-26 months) Per1-luc transgenic rats, entrained to light-dark cycles, were killed, and tissues were removed and cultured. Per1-luc expression was measured from 10 tissues. In the SCN, the central mammalian pacemaker, Per1-luc expression was robustly rhythmic for more than 7 weeks in culture. The only difference between SCN rhythmicity in young and old rats was a small but significant age-related shortening of the free-running period. Circadian rhythmicity in some peripheral tissues was unaffected by aging, whereas rhythmicity in other tissues was either phase advanced relative to the light cycle or absent. Those tissues that were arrhythmic could be induced to oscillate by application of forskolin, suggesting that they retained the capacity to oscillate but were not being appropriately driven in vivo. Overall, the results provide new insights into the effects of aging on the mammalian circadian system. Aging seems to affect rhythms in some but not in all tissues and may act primarily on interactions among circadian oscillators, perhaps attenuating the ability of the SCN to drive damped oscillators in the periphery.

Circadian rhythms in isolated brain regions

The suprachiasmatic nucleus (SCN) of the mammalian hypothalamus has been referred to as the master circadian pacemaker that drives daily rhythms in behavior and physiology. There is, however, evidence for extra-SCN circadian oscillators. Neural tissues cultured from rats carrying the Per-luciferase transgene were used to monitor the intrinsic Per1 expression patterns in different brain areas and their response to changes in the light cycle. Although many Per-expressing brain areas were arrhythmic in culture, 14 of the 27 areas examined were rhythmic. The pineal and pituitary glands both expressed rhythms that persisted for >3 d in vitro, with peak expression during the subjective night. Nuclei in the olfactory bulb and the ventral hypothalamus expressed rhythmicity with peak expression at night, whereas other brain areas were either weakly rhythmic and peaked at night, or arrhythmic. After a 6 hr advance or delay in the light cycle, the pineal, paraventricular nucleus of the hypothalamus, and arcuate nucleus each adjusted the phase of their rhythmicity with different kinetics. Together, these results indicate that the brain contains multiple, damped circadian oscillators outside the SCN. The phasing of these oscillators to one another may play a critical role in coordinating brain activity and its adjustment to changes in the light cycle.

Paroxysmal compulsion to handle keys in a computer operator due to meningioma in the left supplementary motor area

We describe the case of a computer operator who experienced paroxysmal attacks several times in which she felt a compulsion to handle keys with her right hand or actually her right hand moved involuntarily in a key-handling rhythm. Cranial CT and MRI revealed a mass lesion in the left medial aspect of the frontal lobe (supplementary motor area). After the removal of this tumor (meningioma), there were no more paroxysmal attacks. We suggest that voluntary movements controlled by the supplementary motor area were deranged by seizures provoked by the tumor. This case is attractive in relation to obsessive-compulsive disorder.

Topographic mapping of P300 and frontal cognitive function in Parkinson's disease

The purpose of this study was to evaluate the relationship between P300 that is one of the event-related potentials and frontal cognitive functions in Parkinson's disease (PD) without clinically apparent dementia. Subjects were 20 PD cases 48 to 79 years of age, all of whom were within normal limits on the Mini-Mental State examination, and 55 age-matched healthy adults. P300 was elicited with an auditory oddball paradigm and recorded at 15 sites on the scalp. Cognitive functioning of the frontal lobe was evaluated using the New Modified Wisconsin Card Sorting Test (WCST) and the Letter Pick-Out Test (LPOT) which reflects selective attention and semantic categorization. P300 latency was delayed in 30.0% of P300 demonstrated abnormal distribution in 20.0%. the WCST and the LPOT were abnormal in 15.0%, P300 latency significantly correlated with number of subcategories achieved on the WCST. P300 amplitude correlated with scores on the LPOT. These results suggest that cognitive dysfunction which linked partly to the frontal lobe might begin in PD even without clinically apparent dementia.

Entrainment of the circadian clock in the liver by feeding

Circadian rhythms of behavior are driven by oscillators in the brain that are coupled to the environmental light cycle. Circadian rhythms of gene expression occur widely in peripheral organs. It is unclear how these multiple rhythms are coupled together to form a coherent system. To study such coupling, we investigated the effects of cycles of food availability (which exert powerful entraining effects on behavior) on the rhythms of gene expression in the liver, lung, and suprachiasmatic nucleus (SCN). We used a transgenic rat model whose tissues express luciferase in vitro. Although rhythmicity in the SCN remained phase-locked to the light-dark cycle, restricted feeding rapidly entrained the liver, shifting its rhythm by 10 hours within 2 days. Our results demonstrate that feeding cycles can entrain the liver independently of the SCN and the light cycle, and they suggest the need to reexamine the mammalian circadian hierarchy. They also raise the possibility that peripheral circadian oscillators like those in the liver may be coupled to the SCN primarily through rhythmic behavior, such as feeding.

Deteriorating ischemic stroke in 4 clinical categories classified by the Oxfordshire Community Stroke Project

BACKGROUND AND PURPOSE

The aim of this study was to investigate the frequency, possible predictive factors, and prognosis of deteriorating ischemic stroke in 4 clinical categories according to the classification of the Oxfordshire Community Stroke Project (OCSP).

METHODS

A total of 350 patients with first-ever ischemic stroke who presented within 24 hours of onset were enrolled. Based on the OCSP criteria, cerebral infarctions were divided into the following 4 clinical categories: total anterior circulation infarcts (TACI), partial anterior circulation infarcts (PACI), lacunar infarcts (LACI), and posterior circulation infarcts (POCI). Clinical deterioration was defined as a decrease of >/=1 points in the Canadian Neurological Scale (CNS) (in TACI, PACI, and LACI) or Rankin Scale (RS) (in POCI) during 7 days from the onset. In each clinical category, deteriorating (D) and nondeteriorating (ND) patients were compared in terms of their background characteristics, risk factors, vital signs, laboratory data, and cranial CT at the time of hospitalization. The acute-phase mortality and functional outcome were also compared.

RESULTS

The subjects comprised 86 patients (24.6%) with TACI, 63 (18.0%) with PACI, 141 (40.3%) with LACI, and 60 (17.1%) with POCI. Overall, 90 patients (25.7%) deteriorated. The frequency was very high in TACI (41.9%), followed by LACI (26.2%) and POCI (21.7%), whereas it was very low in PACI (6. 3%). There were some clinical variables that differed significantly between D and ND groups. In the patients with TACI, early abnormalities of the cranial CT and significant stenoses in corresponding arteries were more frequent in the D than the ND group. In those with LACI, the CNS and hematocrit were lower in the D than the ND group. In those with POCI, cerebral atrophy was more severe and significant stenoses in vertebrobasilar arteries were more frequent in the D than ND group. The mortality of the D groups of patients with TACI and POCI exceeded 35%, and the functional outcome was worse in the D group than in the ND group of patients with TACI, LACI, and POCI.

CONCLUSIONS

The frequency of deterioration in acute ischemic stroke significantly differed among the OCSP subgroups, and deterioration worsened the prognosis. There were some factors that could predict deterioration: early CT findings in TACI, large-artery atherosclerosis in TACI and POCI, and stroke severity in LACI. Further research to find sophisticated radiological and chemical markers appears to be needed.

The human and mouse Period1 genes: five well-conserved E-boxes additively contribute to the enhancement of mPer1 transcription

The clock gene, Period1, from human and mouse was sequenced and characterized. Both human PERIOD1 (human PER1) and mouse Period1 (mouse Per1) consisted of 23 exons spanning approximately 16 kb, and their structures showed strong similarity to each other. For example, six highly conserved regions were identified in the 5' upstream sequences. These conserved segments exhibited 77-88% identity and possessed several potential regulatory elements including five E-boxes (the binding site of the CLOCK-BMAL1 complex) and four cyclic AMP response elements. Transient transfection assays using a mPer1-luciferase fusion gene revealed that each of the conserved E-boxes additively functions as an enhancer for the transactivation of mPer1 by mCLOCK and mBMAL1.

Resetting central and peripheral circadian oscillators in transgenic rats

In multicellular organisms, circadian oscillators are organized into multitissue systems which function as biological clocks that regulate the activities of the organism in relation to environmental cycles and provide an internal temporal framework. To investigate the organization of a mammalian circadian system, we constructed a transgenic rat line in which luciferase is rhythmically expressed under the control of the mouse Per1 promoter. Light emission from cultured suprachiasmatic nuclei (SCN) of these rats was invariably and robustly rhythmic and persisted for up to 32 days in vitro. Liver, lung, and skeletal muscle also expressed circadian rhythms, which damped after two to seven cycles in vitro. In response to advances and delays of the environmental light cycle, the circadian rhythm of light emission from the SCN shifted more rapidly than did the rhythm of locomotor behavior or the rhythms in peripheral tissues. We hypothesize that a self-sustained circadian pacemaker in the SCN entrains circadian oscillators in the periphery to maintain adaptive phase control, which is temporarily lost following large, abrupt shifts in the environmental light cycle.

Characterization of a novel member of the FGF family, XFGF-20, in Xenopus laevis

The cDNA for a novel member of the FGF family (XFGF-20) was isolated from a Xenopus cDNA library prepared at the tailbud stage using as a probe the product of degenerate PCR performed with primers based on mammalian FGF-9s. This cDNA was 1860 bp long, and contained a single open reading frame that encoded 208 amino acid residues. The deduced amino acid sequence contained a motif characteristic of the FGF family and it was similar (73.1% overall homology) to XFGF-9 but differed from XFGF-9 in its amino-terminal region (33.3% homology). XFGF-20 mRNA was expressed only zygotically in embryos at and after the blastula stage, but it was also specifically expressed in the stomach and testis of adults. By contrast, XFGF-9 mRNA was expressed maternally in eggs and in many adult tissues. When XFGF-20 mRNA was overexpressed in early embryos, gastrulation was abnormal and development of anterior structures was suppressed. In such embryos, the expression of the Xbra transcript was suppressed during gastrulation while the expression of the transcripts of cerberus, Siamois, dkk-1, chordin, and Xotx-2 genes was normal. These results suggest that correct expression of XFGF-20 during gastrulation is required for the formation of normal head structures in Xenopus laevis during embryogenesis and that expression of the Xbra gene mediates this phenomenon.

Monoparesis of the right hand following a localised infarct in the left "precentral knob"

A patient with acute weakness of the righ arm showed a focal lesion on MRI in the left 'precentral knob', not visible on CT.

Correlation between symptomatic, radiological and etiological diagnosis in acute ischemic stroke

OBJECTIVES

The aim of this study was to correlate with the symptomatic, radiological and etiological diagnosis in acute ischemic stroke.

SUBJECTS AND METHODS

Two hundred and fifty patients with first-ever ischemic stroke within 24 h of onset were prospectively studied with 3-step diagnoses: 1) symptomatic diagnosis based on the Oxfordshire Community Stroke Project criteria (OCSP), 2) radiological diagnosis (CT or MRI) and 3) etiological diagnosis based on the Lausanne Stroke Registry criteria.

RESULTS

Most of the patients with symptoms of total anterior circulation infarcts (TACI), partial anterior circulation infarcts (PACI) and posterior circulation infarcts (POCI) had corresponding lesions on CT or MRI, while only 68% of lacunar infarcts (LACI) patients had small subcortical infarction (SSI). More than 60% of patients with TACI were classified into cardioembolism in the third diagnosis, while the etiology of PACI was either CE or large-artery atherosclerosis (LAA) in equal numbers. Only 58% of LACI patients were classified into small-artery disease (SAD) and 29% of them (30 cases) into LAA, of which 23 patients had lesions other than SSI. The positive predictive value of SAD in the combination of LACI and SSI was 0.78. The etiology of POCI was variable.

CONCLUSION

Except for LACI, the symptomatic classification by OCSP corresponds well to the radiological diagnosis. The etiological diagnosis can be predicted by OCSP in TACI and PACI, but it is hard in POCI, and a number of LACI are due to LAA.