Elevated Carbon Dioxide and Litter Decomposition in California Annual Grasslands: Which Mechanisms Matter?

To date, most research that has examined the effect of elevated atmospheric carbon dioxide concentration ([CO₂]) on litter decomposition has focused on changes in the leaf litter quality of individual species. Results from California grasslands indicate that other CO₂ responses may have greater consequences for decomposition rates. For instance, CO₂-driven changes in either species dominance or patterns of biomass allocation would alter both the quality and the position of grassland litter. We review the results from studies in California grasslands to identify the mechanisms that affect grassland litter decomposition. We use a simple calculation that integrates the results of two studies to identify three mechanisms that have the potential to substantially alter decomposition rates as the atmospheric [CO₂] rises. Received 16 January 2001; accepted 26 September 2001.     

Relation Between Personality and Ventilatory Response to Carbon Dioxide in Normal Subjects: A Role in Asthma?

Ventilatory response to carbon dioxide, as an index of respiratory centre sensitivity, was measured in 50 normal subjects. Their personality was documented in terms of extraversion and neuroticism scores by the Eysenck Personality Inventory. A significant correlation was found between extraversion score and ventilatory response to carbon dioxide in women (P < 0·005) but not in men. No correlation was found between ventilatory responsiveness and neuroticism score in either sex. It is suggested that the degree of extraversion may play some part in determining the level of ventilation adopted, and hence of arterial carbon dioxide tension, if and when women develop lung disease such as asthma.     

What counts? Volunteers and their organisations in the recording and monitoring of biodiversity

There is a pressing need for volunteer amateur naturalists to participate in data collection for biodiversity monitoring programmes in Europe. It is being addressed in some countries, but less so in others. This paper discusses the results from qualitative research using semi-structured interviews, focus groups and participant observation within nine Participatory Monitoring Network (PMN) organisations in six European countries. The paper examines the features that facilitate recruitment, retention and motivations of volunteers to participate in biodiversity monitoring, including the social and cultural milieus in which they operate. The paper concludes that volunteers place a high degree of significance on their social experience within PMNs. Successful creation and management of PMNs thus requires that similar levels of attention be paid to social aspects of the organisation as are paid to the generation and management of data.     

Top predator fish assemblages in Northern Patagonia,Argentina. What factors regulate their patterns of distribution and abundance?

According to assemblage theory, three factors regulate fish biogeography: restriction of dispersion, environmental restrictions and biotic interactions. The first two factors act on a regional scale and delimit the area of action of the third, which operates on a local scale. Salmonid introductions began in Patagonia in 1904, and this has led to a restructuring of trophic webs and an increase in the number of top predators. This situation allowed us to evaluate, in a natural setting, how communities are formed on different geographic scales. We studied two large basins in Patagonia, situated close to each other but with different assemblages of top predatory fish. We hypothesized that differences in the structuring of the top predator assemblages between and within the basins are due to 1) environmental factors and dispersion processes facilitated by connectivity on a regional scale; and 2) biotic interaction (internal dynamics) between native perch and salmonids, the former acting as a modulator of the top predator assemblages on a local scale. To test these hypotheses, we analysed the top predator assemblages of 16 lakes and one reservoir, as well as their environmental characteristics. We performed a cluster analysis and related the resulting assembly groups to environmental factors by means of a tree model. We also analysed fish diets, using a similarities test to study biotic interactions. On regional and local scales, water basin, degree of connectivity, area, temperature and Zoogeographic integrity coefficient (ZIC) were important factors in the structuring of top predator assemblages. On a local scale, creole perch modulates the salmonid populations through feeding and the consequent distribution of resources. Our work showed that the structure of top predator assemblages was determined by a combination of local and regional factors acting in synergy, as postulated by the assemblage theory.     

The polyphenolic content of fruit and vegetables and their antioxidant activities. What does a serving constitute?

Analysis of the major flavone, flavonol, anthocyanidin and hydroxycinnamic acid constituents (and their glycosides) of onion, tomato, egg plant and apple has been undertaken and the antioxidant activities of the phenolic extracts determined. The major phenolic antioxidant components of egg plant are chlorogenic acid in the flesh and a delphinidin conjugate in the skin. In the case of apple, the major phenolic antioxidants detected are chlorogenic acid, procyanidins/catechin compounds, rutin and phloridzin. Quercetin glycosides are well-known to be the major phenolic components of onion. Assessment of the antioxidant activities of a serving of 100 g fresh weight fruit, vegetable and comparison with previously reported findings for 150 ml beverage (500 ml portion in the case of beer), expressed in μmol Trolox equivalents show that the antioxidant activities of 1 glass (150 ml) red wine ≡ 12 glasses white wine ≡ 2 cups of tea ≡ 4 apples ≡ 5 portions of onion ≡ 5.5 portions egg plant ≡ 3.5 glasses of blackcurrant juice ≡ 3.5 (500 ml) glasses of beer ≡ 7 glasses of orange juice ≡ 20 glasses of apple juice (long life).     

Does interspecific hybridization influence evolutionary rates? An experimental study of laboratory adaptation in hybrids between Drosophila serrata and Drosophila birchii.

The low initial fitness of progeny from interspecific crosses in animals and the rarity of interspecific hybridization in natural environments have led to a debate about the evolutionary importance of this phenomenon. Here we directly assess the effects of hybridization between Drosophila serrata and Drosophila birchii on evolutionary rates. We looked at the effects on laboratory adaptation over 30 generations in two laboratory environments, one of which involved nutrition and temperature stress. Laboratory adaptation occurred over time in both environments as reflected by a marked change in viability. However, whilst hybrid lines at no stage performed poorly relative to parental lines, their rate of adaptation never exceeded that of the parentals. Thus, there was no evidence that hybridization increased evolutionary rates. Instead, hybrid lines converged phenotypically with one of the parental species.     

Ecological and Genetic Interactions in Drosophila–parasitoids Communities: A Case Study with D. Melanogaster, D. Simulans and their Common Leptopilina Parasitoids in Southe-astern France

Drosophila species are attacked by a number of parasitoid wasps, which constitute an important factor of population regulation. Since Drosophila melanogaster and Drosophila simulans share common parasitoid species, their ecology and evolution can hardly be understood without considering parasitoids. After a short review of data available on Drosophila-parasitoid interactions involving D. melanogaster and D. simulans as hosts, we report field and laboratory experiments investigating the ecological role of Leptopilina parasitoids in Drosophila communities of southern France. Seasonal survey of species abundance shows that strong interspecific interactions occur at both tropic levels. D. simulans progressively replaces D. melanogaster in southern areas suggesting competitive displacement. Parasitoids are responsible for very high Drosophila mortality (up to 90% in some fruits). Field data emphasize the importance of selective pressure that parasitoids exert on Drosophila communities. The two Leptopilina parasites (L. heterotoma and L boulardi) have different local abundances, which vary in time, and they also compete for hosts. We show that parasitoids can mediate the coexistence of D. melanogaster and D. simulans in the laboratory, and thus may contribute to their puzzling coexistence in the field. Conversely, hosts exert selective pressures on parasitoids, and development on either D. melanogaster or D. simulans strongly affects fitness of adult wasps in a temperature-dependent fashion. Local variation in host species abundance and diversity could thus account for the genetic differentiation we observed in one parasitoid species. Despite laboratory studies cannot fully explain complex field situations, it is clear that the ecology and evolution of Drosophila populations and communities, especially D. melanogaster and D. simulans, are strongly constrained by parasitoids, which should receive more attention.     

What really matters in end-of-life discussions? Perspectives of patients in hospital with serious illness and their families

Background:

The guideline-recommended elements to include in discussions about goals of care with patients with serious illness are mostly based on expert opinion. We sought to identify which elements are most important to patients and their families.

Methods:

We used a cross-sectional study design involving patients from 9 Canadian hospitals. We asked older adult patients with serious illness and their family members about the occurrence and importance of 11 guideline-recommended elements of goals-of-care discussions. In addition, we assessed concordance between prescribed goals of care and patient preferences, and we measured patient satisfaction with goals-of-care discussions using the Canadian Health Care Evaluation Project (CANHELP) questionnaire.

Results:

Our study participants included 233 patients (mean age 81.2 yr) and 205 family members (mean age 60.2 yr). Participants reported that clinical teams had addressed individual elements of goals-of-care discussions infrequently (range 1.4%–31.7%). Patients and family members identified the same 5 elements as being the most important to address: preferences for care in the event of life-threatening illness, values, prognosis, fears or concerns, and questions about goals of care. Addressing more elements was associated with both greater concordance between patients’ preferences and prescribed goals of care, and greater patient satisfaction.

Interpretation:

We identified elements of goals-of-care discussions that are most important to older adult patients in hospital with serious illness and their family members. We found that guideline-recommended elements of goals-of-care discussions are not often addressed by health care providers. Our results can inform interventions to improve the determination of goals of care in the hospital setting.In Canada, dying is often an in-hospital, technology-laden experience.^1–4 Rates of cardiopulmonary resuscitation (CPR) before death continue to increase among older adult patients in hospital,⁵ and one-fifth of deaths in hospital occur in an intensive care unit.^1,2,6,7 These observations contrast sharply with patient-reported preferences. A recent Canadian study found that 80% of older adult patients in hospital with a serious illness prefer a less aggressive and more comfort-oriented end-of-life care plan that does not include CPR.⁸Such patients and their families have identified communication with health care providers and decision-making about goals of care as high priorites for improving end-of-life care in Canada.^9,10 We define “decision-making about goals of care” as an end-of-life communication and decision-making process that occurs between a clinician and a patient (or a substitute decision-maker if the patient is incapable) in an institutional setting to establish a plan of care. Often, this process includes deciding whether to use life-sustaining treatments.¹¹ Current guidelines recommend that health care providers address 11 key elements when discussing goals of care with patients and families (Box 1).^12–14 However, these elements are mostly based on expert opinion and lack input from patients and their families.

Box 1:

Key elements of goals-of-care discussions with patients in hospital with serious illness^12–14

• Ask about previous discussions or written documentation about the use of life-sustaining treatments
• Offer a time to meet to discuss goals of care
• Provide information about advance care planning to review before conversations with the physician
• Disclose prognosis
• Ask about patients’ values (i.e., what is important to them when considering health care decisions)
• Provide information about outcomes, benefits and risks of life-sustaining treatments
• Provide information about outcomes, benefits and risks of comfort measures
• Prompt for additional questions about goals of care
• Provide an opportunity to express fears or concerns
• Ask about preferences for care in the event of a life-threatening illness
• Facilitate access to legal documents to record patients’ wishes

Our primary objective was to determine which of these elements are most important to patients and their families. In addition, we examined whether these discussions were associated with concordance between patients’ (or family members’) preferences and prescribed goals of care, and with satisfaction with end-of-life communication and decision-making.     

What does the fruitless gene tell us about nature vs. nurture in the sex life of Drosophila?

The fruitless (fru) gene in Drosophila has been proposed to play a master regulator role in the formation of neural circuitries for male courtship behavior, which is typically considered to be an innate behavior composed of a fixed action pattern as generated by the central pattern generator. However, recent studies have shed light on experience-dependent changes and sensory-input-guided plasticity in courtship behavior. For example, enhanced male-male courtship, a fru mutant “hallmark,” disappears when fru-mutant males are raised in isolation. The fact that neural fru expression is induced by neural activities in the adult invites the supposition that Fru as a chromatin regulator mediates experience-dependent epigenetic modification, which underlies the neural and behavioral plasticity.     

The role of gut hormones in controlling the food intake. What is their role in emerging diseases?

Central nervous system (CNS) receives peripheral relevant information that are able to regulate individual's energy balance through metabolic, neural, and endocrine signals. Ingested nutrients come into contact with multiple sites in the gastrointestinal tract that have the potential to alter peptide and neural signaling. There is a strong relationship between CNS and those peripheral signals (as gastrointestinal hormones) in the control of food intake. The purpose of this review is to give updated information about the role of gut hormones as mediators of feeding behavior and of different nutrients in modulating gut hormones production. The role of gut hormones in the pathogenesis of emerging diseases as obesity and non-alcoholic fatty liver disease (NAFLD) is also discussed together with the possible role of these peripheral signals as targets of future therapeutic options.     

What is winter? Modeling spatial variation in bat host traits and hibernation and their implications for overwintering energetics

White‐nose syndrome (WNS) has decimated hibernating bat populations across eastern and central North America for over a decade. Disease severity is driven by the interaction between bat characteristics, the cold‐loving fungal agent, and the hibernation environment. While we further improve hibernation energetics models, we have yet to examine how spatial heterogeneity in host traits is linked to survival in this disease system. Here, we develop predictive spatial models of body mass for the little brown myotis (Myotis lucifugus) and reassess previous definitions of the duration of hibernation of this species. Using data from published literature, public databases, local experts, and our own fieldwork, we fit a series of generalized linear models with hypothesized abiotic drivers to create distribution‐wide predictions of prehibernation body fat and hibernation duration. Our results provide improved estimations of hibernation duration and identify a scaling relationship between body mass and body fat; this relationship allows for the first continuous estimates of prehibernation body mass and fat across the species'' distribution. We used these results to inform a hibernation energetic model to create spatially varying fat use estimates for M. lucifugus. These results predict WNS mortality of M. lucifugus populations in western North America may be comparable to the substantial die‐off observed in eastern and central populations.     

What are the characteristics of lionfish and other fishes that influence their association in diurnal refuges?

In Caribbean reefs, the lionfish Pterois volitans is an invasive species that causes severe negative ecological effects, especially as this crepuscular predator consumes very diverse prey. Lionfish are not active during the day and stay in their refuges, sharing these spaces with various other fishes. The aim of this study is to determine which fishes are associated with the lionfish in their shelters, and what characteristics of both the invasive and native species may influence and explain such coexistence between a predator and its potential prey. Through diving and snorkelling, we visited 141 lionfish refuges, mostly caves, where we observed 204 lionfish and 494 other fish from 16 native species. We recorded species and abundance, as well as lionfish size and abundance. Half of the lionfish were observed in groups and the majority were large-sized. The association with most fish species seems fortuitous, but three species, Gramma loreto, Chromis cyanea and Canthigaster rostrata, were frequently observed in association with lionfish. Numerous fish juveniles, most likely Scarus coeruleus, were also observed together with the invasive predator. The more commonly associated fishes, particularly G. loreto, are mostly associated with large-sized lionfish that were found in groups. The associated fishes are also generally found in groups. Gramma loreto is a potential cleaner of the lionfish; the reasons for the association between these fish species and the invasive lionfish may be more complex than a simple predator-prey relationship and are discussed based on their biological traits and previously reported lionfish trophic ecology and predation behaviour.     

Molecular polymorphism in Drosophila melanogaster and D. simulans: what have we learned from recent studies?

We present a review of recent studies of molecular polymorphism in Drosophila melanogaster and D. simulans. The availability of African and non-African samples for these species makes it possible to compare microsatellite and DNA sequence polymorphism between these species, both inside and outside their native regions. There are four main results: (i) variability is larger in African populations; (ii) variation is usually higher on the autosomes, except for African D. melanogaster; (iii) DNA sequence variation is higher on D. simulans than on D. melanogaster autosomes; (iv) the ratio of replacement to silent polymorphisms is higher for D. melanogaster autosomal loci. We summarize the main hypotheses put forward to explain these results.     

Spitzenk?rper,Exocyst, and Polarisome Components in Candida albicans Hyphae Show Different Patterns of Localization and Have Distinct Dynamic Properties

During the extreme polarized growth of fungal hyphae, secretory vesicles are thought to accumulate in a subapical region called the Spitzenkörper. The human fungal pathogen Candida albicans can grow in a budding yeast or hyphal form. When it grows as hyphae, Mlc1 accumulates in a subapical spot suggestive of a Spitzenkörper-like structure, while the polarisome components Spa2 and Bud6 localize to a surface crescent. Here we show that the vesicle-associated protein Sec4 also localizes to a spot, confirming that secretory vesicles accumulate in the putative C. albicans Spitzenkörper. In contrast, exocyst components localize to a surface crescent. Using a combination of fluorescence recovery after photobleaching (FRAP) and fluorescence loss in photobleaching (FLIP) experiments and cytochalasin A to disrupt actin cables, we showed that Spitzenkörper-located proteins are highly dynamic. In contrast, exocyst and polarisome components are stably located at the cell surface. It is thought that in Saccharomyces cerevisiae exocyst components are transported to the cell surface on secretory vesicles along actin cables. If each vesicle carried its own complement of exocyst components, then it would be expected that exocyst components would be as dynamic as Sec4 and would have the same pattern of localization. This is not what we observe in C. albicans. We propose a model in which a stream of vesicles arrives at the tip and accumulates in the Spitzenkörper before onward delivery to the plasma membrane mediated by exocyst and polarisome components that are more stable residents of the cell surface.Polarized growth of fungi requires that a supply of secretory vesicles is delivered along cytoskeletal tracks to the site of cell expansion (for reviews, see references 13, 29, 30, and 31). Fusion of these membrane-bound vesicles with the plasma membrane allows the necessary expansion of the plasma membrane and releases the enzymes and raw materials for the synthesis of new cell wall material and the remodeling necessary to allow this newly synthesized material to be inserted into the existing cell wall. The process of polarized growth has been extensively studied in the budding yeast Saccharomyces cerevisiae and provides a model for studying the process in other fungi (for a review, see reference 20). Post-Golgi vesicles travel to sites of polarized growth along actin cables (23). Actin cables are nucleated at sites of polarized growth by the formin Bni1 facilitated by a multiprotein complex called the polarisome, which consists of Spa2, Bud6, and Pea1(5, 22, 24, 27). The motive force for vesicle transport is provided by Myo2, a class V myosin, complexed to its regulatory light chain Mlc1 (22, 26). At the plasma membrane, secretory vesicles dock with a second multiprotein complex called the exocyst before fusion with the plasma membrane (14, 15, 32, 33), mediated by v-SNARES on the vesicle and t-SNARES on the membrane. The exocyst is an octomeric complex composed of Sec3, Sec5, Sec6, Sec8, Sec10, Sec15, Exo70, and Exo84 (21). It is thought that Sec3 and a fraction of the Exo70 pool are localized at sites of polarized growth independently of the actin cytoskeleton (3, 6). The other exocyst subunits and the remainder of the Exo70 pool are thought to be transported to sites of polarized growth on secretory vesicles, where together with Sec3 and Exo70 they form the exocyst complex (3). Secretory vesicles exit the Golgi apparatus, travel toward sites of polarized growth, and dock with the exocyst by use of the Rab-type GTPase Sec4 in its GTP-bound form, which is activated by its GEF, Sec2 (12, 19, 35, 36). In the S. cerevisiae cell cycle, polarized growth is initially directed toward the bud tip in young buds (17). Growth subsequently becomes isotropic in larger buds before being directed toward the mother bud neck during cytokinesis at the end of the cell cycle. Accordingly, polarisome and exocyst components localize to the tips of young buds (7, 27, 28).The rate of hyphal tip extension is much greater than that of the growth of a yeast or pseudohyphal bud. In rich yeast extract-peptone-dextrose (YEPD) medium, Candida albicans hyphae extend at the rate of 0.25 μm min⁻¹, compared to 0.0625 μm min⁻¹ in yeast buds and 0.125 μm min⁻¹ in pseudohyphal cells (P. Sudbery unpublished observations). In hyphae of filamentous fungi, a structure called a Spitzenkörper is present at the tip, which is rich in secretory vesicles (8, 9, 11, 29, 34). It is believed that the Spitzenkörper acts as a vesicle supply center (VSC) (1). This model proposes that the Spitzenkörper is maintained at a fixed distance from the hyphal tip. Vesicles radiate out in equal directions to fuse with the plasma membrane, so that more vesicles per unit area fuse with the hyphal tip itself than with other parts of the hyphae. Mathematical modeling shows that this explains the distinctive shape of hyphal tips.In order to investigate the mechanism of polarized growth in the hyphae of Candida albicans, we previously determined the localization of Mlc1-yellow fluorescent protein (YFP) and the polarisome components Bud6-YFP and Spa2-YFP (4). We found that in hyphae, polarisome components localized to a surface crescent, as they did in young yeast buds and the tips of elongated pseudohyphal buds. However, in hyphae Mlc1-YFP localized to a bright spot, which at least in some hyphae was clearly inside the tip, rather than at the surface, and which appeared spherical in three-dimensional reconstructions. We concluded that this represented a Spitzenkörper. In some hyphae Mlc1-YFP also localized to a surface crescent, similar to the pattern displayed by polarisome components. This observation suggested that the Spitzenkörper and polarisome were separate structures, both of which were present at hyphal tips, but that only the polarisome was present at the bud tips of pseudohyphae and yeast. Moreover, the dual localization of Mlc1-YFP to a crescent and a spot suggested that Mlc1 may be present in both structures.While S. cerevisiae has proved to be an excellent model to investigate the molecular genetics of polarized growth, it is less optimal to study the spatial organization of the molecular components because polarized growth of the bud is restricted to a short period after bud emergence when the nascent bud is small. Thus, there has been little effort to investigate the fine detail of the spatial organization of the different components of the polarization machinery beyond noting that they localize to sites of polarized growth. In this study we exploited the opportunities afforded by the continuous polarized growth of C. albicans hyphae to clarify the relationship between the Spitzenkörper, polarisome, and exocyst, which cooperate to mediate the extreme polarized growth of hyphae. We show that the vesicle-associated marker Sec4 also localizes to a Spitzenkörper-like structure, confirming the existence of a vesicle-rich area corresponding to a Spitzenkörper at the hyphal tip. We show that exocyst components such as Sec3, Sec6, Sec8, Exo70, and Exo84 localize to a surface crescent, so the exocyst, like the polarisome, is also a spatially separate structure from the Spitzenkörper. We used three independent strategies to investigate the dynamic properties of these structures. Fluorescence recovery after photobleaching (FRAP) was used to measure the rate at which new proteins arrived at the tip. Fluorescence loss in photobleaching (FLIP) was used to measure the rate at which proteins exited the tip. Cytochalasin A was used to disrupt actin cables, allowing the persistence of proteins at the tip to be measured after the supply of new proteins was blocked. In each case we found that Spitzenkörper components Sec4, Sec2, and Mlc1 were highly dynamic, while the polarisome component Spa2 was stable. Intriguingly, exocyst components showed intermediate dynamic properties, suggesting that they are delivered to the tip on vesicles but that not all vesicles carry a complement of exocyst components. We suggest that these data are consistent with a model in which a stream of vesicles arrives at the tip and accumulates in the Spitzenkörper before onward delivery to the plasma membrane mediated by exocyst and polarisome components that are more stable residents of the cell surface.     

Costello syndrome in two siblings and minor manifestations in their mother. Further evidence for autosomal dominant inheritance?

We report on two siblings: the index patient, a 9 months old boy and his 2.5 years old sister, both presenting the main clinical signs and symptoms of Costello syndrome (CS): severe mental and motor retardation, feeding difficulties, failure to thrive in the first months of life, coarse facial appearance, skin hyperlaxity and skeletal deformities. Their mother presented with mild to moderate mental retardation, short stature, facial fullness and wart-like lesions on her face. The present observation confirms previous data on the apparent autosomal dominant pattern of inheritance in Costello syndrome with variable expression.     

Photoendocrine Transduction in Cultured Chick Pineal Cells: IV. What Do Vitamin A Depletion and Retinaldehyde Addition Do to the Effects of Light on the Melatonin Rhythm?

Abstract: Light has at least two distinguishable effects on the circadian rhythm of melatonin output displayed by dispersed chick pineal cells in static culture: acute suppression of melatonin output and entrainment (phase shifts) of the underlying pacemaker. Previous results indicated that these two effects of light are mediated by different mechanistic pathways. The pathways for the acute and phase-shifting effects of light either branch from the same, single photopigment or differ from the outset, starting from separate photopigments. If a single rhodopsin-like photopigment mediates both effects of light, then vitamin A depletion and retinoid addition should affect both responses in parallel, although not proportionately. We therefore compared the effects of vitamin A depletion and retinoid addition on the acute and phase-shifting effects of light under several experimental conditions. When chick pineal cells were depleted of vitamin A, acute responses to light were markedly reduced. Addition of 11-cis-retinaldehyde specifically restored (and enhanced) the acute response. When allowed to free run in constant red light, depleted cells displayed a rhythm of melatonin output with the same period as that of control cells. In contrast to the acute effects, phase shifts in response to 2- or 4-h light pulses did not differ between depleted and control cells. Addition of retinaldehyde to depleted cells did not, by itself, reduce melatonin output or induce phase shifts. Retinaldehyde did increase the acute response to 4-h light pulses but not the ensuing phase shifts. Responses increased with duration of the light pulse: Both the acute effect and the phase shifts induced by 4-h light pulses were considerably larger than those induced by 2-h (or 1-h) light pulses. Addition of retinaldehyde to depleted cells increased the acute effect of 2-h (or 1-h) light pulses to at least that seen with 4-h light pulses but did not Increase the size of the ensuing phase shifts. These results strongly confirm previous dissociations of the mechanistic pathways mediating the acute and phase-shifting effects of light on chick pineal cells. They also support a role for rhodopsin-like photopigment in the acute, but not phase-shifting, response. They favor, but do not prove, the conclusion that separate photopigments mediate the acute and entraining effects of light.     

The Role and Dynamic of Strengthening in the Reconsolidation Process in a Human Declarative Memory: What Decides the Fate of Recent and Older Memories?

Several reports have shown that after specific reminders are presented, consolidated memories pass from a stable state to one in which the memory is reactivated. This reactivation implies that memories are labile and susceptible to amnesic agents. This susceptibility decreases over time and leads to a re-stabilization phase usually known as reconsolidation. With respect to the biological role of reconsolidation, two functions have been proposed. First, the reconsolidation process allows new information to be integrated into the background of the original memory; second, it strengthens the original memory. We have previously demonstrated that both of these functions occur in the reconsolidation of human declarative memories. Our paradigm consisted of learning verbal material (lists of five pairs of nonsense syllables) acquired by a training process (L1-training) on Day 1 of our experiment. After this declarative memory is consolidated, it can be made labile by presenting a specific reminder. After this, the memory passes through a subsequent stabilization process. Strengthening creates a new scenario for the reconsolidation process; this function represents a new factor that may transform the dynamic of memories. First, we analyzed whether the repeated labilization-reconsolidation processes maintained the memory for longer periods of time. We showed that at least one labilization-reconsolidation process strengthens a memory via evaluation 5 days after its re-stabilization. We also demonstrated that this effect is not triggered by retrieval only. We then analyzed the way strengthening modified the effect of an amnesic agent that was presented immediately after repeated labilizations. The repeated labilization-reconsolidation processes made the memory more resistant to interference during re-stabilization. Finally, we evaluated whether the effect of strengthening may depend on the age of the memory. We found that the effect of strengthening did depend on the age of the memory. Forgetting may represent a process that weakens the effect of strengthening.