bluuebunny/crossref_metadata_2025 huggingface dataset:
Perinatal Influences of Melatonin on Testicular Development and Photoperiodic Memory in Siberian Hamsters
Authors: Tuthill C. R. , Freeman D. A. , Butler M. P. , Chinn Tori , Park J. H. , Zucker I.
Published: July 2005

We assessed the influence of perinatal melatonin on reproductive development and adult responsiveness to melatonin. Testicular growth in an intermediate day length (14 : 10 h light/dark cycle) was substantially reduced in Siberian hamsters gestated by pinealectomised compared to pineal‐intact females; gonadal development was normalised in offspring of pinealectomised dams that were pinealectomised at 3–4 days of age. Hamsters deprived of melatonin only during gestation, or both pre‐ and postnatally, underwent testicular involution during treatment with melatonin in adulthood. Photoperiodic histories acquired prenatally did not endure as long as those acquired by adult hamsters. Hamsters first exposed to melatonin in adulthood were not more proficient in acquiring photoperiodic histories than were normal males. These findings indicate that pre‐ versus postnatal differences in melatonin signal duration determine rates of testicular development. Exposure to melatonin perinatally does not appear to organise the neuroendocrine substrate that mediates effects of day length and melatonin on the gonads of adult hamsters.
Altered Mesencephalic Dopaminergic Populations in Adulthood as a Consequence of Brief Perinatal Glucocorticoid Exposure
Authors: McArthur S. , McHale E. , Dalley J. W. , Buckingham J. C. , Gillies G. E.
Published: July 2005

Early exposure to stressors is strongly associated with enduring effects on central nervous system function, but the mechanisms and neural substrates involved in this biological ‘programming’ are unclear. This study tested the hypothesis that inappropriate exposure to glucocorticoid stress hormones (GCs) during critical periods of development permanently alters the mesencephalic dopaminergic populations in the ventral tegmental area (VTA) and substantia nigra pars compacta (SNc). Using a rat model, the synthetic GC dexamethasone was added to the maternal drinking water during gestational days 16–19 or over the first week of postnatal life. In adulthood, the effects upon tyrosine hydroxylase immunopositive (TH+) cell numbers in the midbrain, and monoamine levels in the forebrain, of the adult offspring were assessed and compared with control offspring whose dams received normal drinking water. In the VTA, both prenatal and postnatal dexamethasone treatment increased TH+ cell numbers by approximately 50% in males and females. Although prenatal dexamethasone treatment also increased TH+ cell numbers in the SNc by 40–50% in males and females, postnatal treatment affected females only by increasing TH+ cell numbers by approximately 30%. In comparison, similar changes were not detected in the monoamine levels of the dorsolateral striatum, nucleus accumbens or infralimbic cortex of either males or females, which is a feature likely to reflect adaptive changes in these pathways. These studies demonstrate that the survival or phenotypic expression of VTA and SNc dopaminergic neurones is profoundly influenced by brief perinatal exposure to GCs at times when endogenous levels are normally low. These findings are the first to demonstrate permanent changes in the cytoarchitecture within midbrain dopamine nuclei after perinatal exposure to stress hormones and implicate altered functionality. Thus, they have significance for the increasing use of GCs in perinatal medicine and indicate potential mechanisms whereby perinatal distress may predispose to the development of a range of psychiatric conditions in later life.
Evidence that the Type‐2 Gonadotrophin‐Releasing Hormone (GnRH) Receptor Mediates the Behavioural Effects of GnRH‐II on Feeding and Reproduction in Musk Shrews
Authors: Kauffman A. S. , Wills A. , Millar R. P. , Rissman E. F.
Published: July 2005

Gonadotrophin‐releasing hormone (GnRH) is a regulatory neuropeptide of which there are multiple structural variants. In mammals, a hypothalamic form (GnRH‐I) controls gonadotrophin secretion whereas a midbrain form (GnRH‐II) appears to have a neuromodulatory role affecting feeding and reproduction. In female musk shrews and mice, central administration of GnRH‐II reinstates mating behaviour previously inhibited by food restriction. In addition, GnRH‐II treatment also decreases short‐term food intake in musk shrews. GnRH‐II can bind two different mammalian GnRH receptors (type‐1 and type‐2), and thus it is unclear which receptor subtype mediates the behavioural effects of this peptide. Adult female musk shrews implanted with i.c.v. cannula were food restricted or fed ad lib and then tested for sexual behaviour or food intake. One hour before testing, animals were pretreated with vehicle or Antide, a potent type‐1 GnRH receptor antagonist (at a dose that blocks GnRH‐I or ‐II mediated ovulation). Twenty minutes before testing, females were infused a second time with either GnRH‐II or vehicle. Additional females were tested after an infusion of 135‐18, a type‐1 receptor antagonist that displays agonist actions at the primate type‐2 receptor. GnRH‐II treatment increased sexual behaviour in underfed female shrews; pretreatment with Antide did not block this action, suggesting that the effects of GnRH‐II are not mediated via the type‐1 receptor. Similarly, the inhibitory effects of GnRH‐II on short‐term food intake were not prevented by pretreatment with Antide. The behavioural effects of the type‐2 receptor agonist 135‐18 were similar to those seen in GnRH‐II‐treated females, with 135‐18 promoting sexual behaviour and decreasing food intake. Collectively, these results indicate that GnRH‐II does not act via the type‐1 GnRH receptor to regulate mammalian behaviour but likely activates the type‐2 GnRH receptor.
Stress‐Induced Changes in Spatial Memory are Sexually Differentiated and Vary Across the Lifespan
Authors: Bowman R. E.
Published: July 2005

Stress exposure, depending on intensity and duration, elicits adaptive or maladaptive physiological changes. The same general pattern of advantageous versus deleterious stress effects appears to exist for some cognitive functions, particularly spatial learning and memory performance. This article reviews sex differences in response to stress on a variety of spatial tasks. In general, females are more resistant than males to stress‐induced impairments on spatial tasks, including the radial arm maze and object placement. In young adulthood, chronic stress (restraint, 6 h per day for 21 days) impairs male performance on both tasks but leads to behavioural enhancements in females. Furthermore, these sex‐dependent stress effects are influenced by both organisational and activational oestrogenic effects. Additionally, sex‐specific stress responses vary depending on developmental age at the time of stress exposure. Male behavioural stress responses appear fixed across the lifespan (i.e. stress‐induced cognitive impairments) whereas female stress responses appear more variable (i.e. stress‐induced enhancements observed in young adulthood are different in response to prenatal stress and diminished following stress exposure at old age). These findings underscore the point that many effects obtained in males cannot be generalised to females and highlight the need to investigate the stress response at different ages and in both sexes.
Prostaglandin E2 Mediates Cellular Effects of Interleukin‐1β on Parvocellular Neurones in the Paraventricular Nucleus of the Hypothalamus
Authors: Ferri C. C. , Ferguson A. V.
Published: July 2005

Interleukin‐1β (IL‐1β) is involved in hypothalamic regulation of corticotrophin‐releasing hormone secretion, autonomic activation and consequent downstream modulation of the neuroimmune response. Previously, we have shown that IL‐1β depolarises parvocellular neurones in the paraventricular nucleus (PVN) of the hypothalamus, and these effects are dependent on attenuation of γ‐amino butyric acid (GABA)‐ergic input. In the present study, using whole‐cell patch clamp recordings of rat neurones in a slice preparation of the PVN, we show that the effects of IL‐1β are abolished in the presence of a cyclooxygenase (COX)‐2 inhibitor, NS‐398, indicating a dependence on prostaglandin (PG) synthesis and activation. In response to 1 µM PGE2, 64% of parvocellular neurones tested exhibited a clear depolarisation, which was abolished in the presence of tetrodotoxin (TTX). Furthermore, neurones responsive to both IL‐1β and PGE2 exhibited a decrease in the frequency of inhibitory post‐synaptic potentials, suggesting that effects of these modulators are mediated via a decrease in GABA‐ergic input to these neurones. A proportion (44% and 40%, respectively) of putative GABA‐ergic neurones in the halo region surrounding the PVN demonstrated hyperpolarising responses to 1 nM IL‐1β and 1 µM PGE2, and these effects were maintained in TTX. Furthermore, direct hyperpolarising effects of IL‐1β were blocked in the presence of NS‐398. Together, these data suggest that PGE2, synthesised in response to IL‐1β‐activation of COX‐2 expressing cells, directly hyperpolarises putative GABA‐ergic neurones in the halo zone surrounding and projecting to the PVN, resulting in a decrease in GABA‐ergic input to parvocellular neurones and consequent depolarisation. These data further elucidate the cellular mechanisms by which IL‐1β exerts its neuroimmune‐related actions in the PVN.
Oestrogens Prevent Loss of Dopamine Transporter (DAT) and Vesicular Monoamine Transporter (VMAT2) in Substantia Nigra of 1‐Methyl‐4‐Phenyl‐1,2,3,6‐Tetrahydropyridine Mice
Authors: Jourdain S. , Morissette M. , Morin N. , Di Paolo T.
Published: July 2005

Previous results from our laboratory have shown that 17β‐oestradiol prevents 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP) striatal dopamine depletion. 17β‐oestradiol, oestriol and oestrone are the naturally occurring oestogens in humans. Using various dopamine markers, the present study investigated whether oestrone and oestriol such as 17β‐oestradiol have neuroprotective activity in MPTP‐treated mice. Male mice were treated with 17β‐oestradiol, oestriol or oestrone for 5 days before and after MPTP administration, and were compared with nonlesioned mice receiving the same treatment. Striatal concentrations of dopamine and its metabolites, 3,4‐dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), were assayed by high‐performance liquid chromatography. Dopamine transporter (DAT) and vesicular monoamine transporter (VMAT2) specific binding were measured by autoradiography. DAT, VMAT2 and tyrosine hydroxylase mRNA levels were measured byin situhybridisation. MPTP induced a loss of DAT and VMAT2 specific binding in the striatum and substantia nigra, as well as a decrease of VMAT2 mRNA in the substantia nigra. 17β‐oestradiol treatment prevented the loss of these dopaminergic markers, as well as striatal concentrations of dopamine, DOPAC and HVA. Mice receiving oestriol and oestrone showed catecholamine concentrations comparable to MPTP mice. Oestriol treatment had no effect on dopaminergic markers in MPTP mice whereas oestrone prevented striatal DAT loss and the decrease of VMAT2 mRNA in the substantia nigra. In nonlesioned mice, 17β‐oestradiol,oestriol or oestrone had no effect on all the dopaminergic markers investigated. In conclusion, a weak or a lack of effect of oestriol and oestrone was observed compared to 17β‐oestradiol in MPTP mice and none of these steroids had an effect in nonlesioned mice. A DAT and VMAT2 specific binding decrease after MPTP in the striatum and substantia nigra, as well as a decrease of substantia nigra VMAT2 mRNA, was observed and could be prevented by oestradiol.
Implementing a self‐management model of relapse prevention for psychosis into routine clinical practice
Authors: STEVENS S. , SIN J.
Published: July 2005

This paper describes an implementation project to incorporate an evidence‐based, structured model of relapse prevention into routine clinical practice at the Community Mental Health Team in Reading, Berkshire. This project has currently reached the end of the pilot stage, which this paper reports in details. It is proposed that clinicians will adopt Smith's Self‐Management Training Manual for individuals with psychosis as a clinical tool for working with patients who have schizophrenic‐form disorders or bipolar affective disorders with psychosis. Effects of the proposed change are considered from the viewpoint of the clients and families/carers, the clinicians and the service. The process of transition and its impact on members of the multidisciplinary team is examined. It includes an audit of Care Programme Approach (CPA) forms and a staff survey, which give background information on the needs for improvement and staff development initiatives. A pilot study incorporating the structured relapse prevention work into the local community mental health team is also underway. The method of evaluation and dissemination to the wider team and service settings across the organizational boundaries is reviewed with implications for practice drawn. This paper aims to describe the background and development of this ongoing development project whilst focusing on the current pilot stage. Ongoing work will be carried out in addressing and reporting the outcomes of the full project in future papers.
Mental health nurses, promoters of inclusion or perpetuators of exclusion?
Authors: BERTRAM G. , STICKLEY T.
Published: July 2005

The literature identifies that mental health services and those individuals working within them have the potential to facilitate inclusion for their client group, because of their power to initiate potential inclusive opportunities. However, evidence suggests that service users themselves perceive many aspects of mental health services as contributing to the problem of exclusion. This has been attributed to an accumulation of messages, attitudes and disempowering practices that have emanated from mental health care providers over a long period. This study employs focus group methodology in a residential rehabilitation unit in an industrial city in the UK. Discussion of the findings highlight how, in spite of alleged inclusive practices, the attitudes held by members of the unit team could impede the clients’ opportunities to become socially included, as a result of defensive practice, paternalistic attitudes, expectations of the local community upon the team and the stagnant views that are embedded in the culture of mental health services. While mental health nurses may see themselves as promoting inclusion, the reality may be quite different.
Factors influencing the effectiveness of clinical supervision
Authors: EDWARDS D. , COOPER L. , BURNARD P. , HANNINGAN B. , ADAMS J. , FOTHERGILL A. , COYLE D.
Published: July 2005

Clinical supervision is widely accepted as an essential prerequisite for high quality nursing care. This paper reports findings from a study that aims to identify the factors that may influence the effectiveness of clinical supervision for community mental health nurses (CMHNs) in Wales, UK. Two hundred and sixty (32%) CMHNs from an estimated total population of 817 completed the Manchester Clinical Supervision Scale (MCCS) and a demographic questionnaire. The MCCS is a 36‐item questionnaire measuring the quality and effectiveness of the supervision received. Three‐quarters of CMHNs reported having participated in six or more sessions of supervision in their current posts. Clinical supervision was more positively evaluated where sessions lasted for over one hour, and took place on at least a once‐monthly basis. Perceived quality of supervision was also higher for those nurses who had chosen their supervisors, and where sessions took place away from the workplace. These findings have important implications for the organization and delivery of mental health nursing services.
Is psychosocial rehabilitation of schizophrenic patients preventing family burden? A comparative study
Authors: KOUKIA E. , MADIANOS M. G.
Published: July 2005

This study examined the dimensions of perceived burden by caregivers‐relatives of patients suffering from schizophrenia and participating in a rehabilitation programme (group A) compared to a group of patients and their corresponding caregivers who were maintained in regular treatment procedure (group B). Subjective and objective burden perceived by caregivers group A patients attending a rehabilitation programme, was found to be lower compared to that of group B of caregivers of patients in regular maintenance treatment. Low level of functioning of patients was correlated with higher degree of family burden and the more psychological distress of the caregiver. The patient's compliance with medication and psychosocial functioning as well as the participation in a rehabilitation programme, the diagnostic subtypes and the mean daily hours spent with the patient were found to predict the presence of burden of caregiver. It seems that the various socio‐therapeutic activities of rehabilitation improve patient's levels of psychosocial functioning, and alleviate the serious psychosocial and emotional problems of caregivers caused by their relative's chronic and severe illness.
A study of three measures of expressed emotion in a sample of Chinese families of a person with schizophrenia
Authors: LI Z. , ARTHUR D.
Published: July 2005

Emotional climate or expressed emotion (EE) has been examined in families of white descent who have a family member with schizophrenia but few studies have been conducted in Asian or Chinese families. This study tested the utility of the five‐minute interview (FMI), adjective checklist (ACL) and family attitude scale (FAS) in a sample of Chinese family members in Beijing, in an attempt to introduce useful measures of EE into practice. A sample of 51 family members were interviewed and administered the three instruments. A total of 29.4% of families were found to be high‐EE critical and 13.7% high‐EE emotional over involvement using the FMI. The FAS and ACL prove internally consistent and were significantly correlated but not with the FMI. Cultural explanations for the discrepancies are offered. The measures have applicability in terms of understanding family relationships but further research and replication is necessary to deepen our understanding of EE in Chinese families.
Neuroleptic medication and sexuality: the forgotten aspect of education and care
Authors: HIGGINS A. , BARKER P. , BEGLEY C. M.
Published: July 2005

Discussing issues of sexuality is a challenging and difficult issue for many health care workers. When it comes to sexuality and people with mental health problems there seems to be a dual taboo. Mental health nurses are ideal members of the health care team to talk to service users about issues as sensitive as sexuality and the side effects of medication that impact on sexual health. However, in both clinical practice and the nursing literature, the side effects of medications that impact on sexual function are often ignored and unspoken about. This paper examines the impact of both conventional and atypical neuroleptic medication on sexual function and discusses the probable causes of such effects. The possible reasons why health care professionals are reluctant to discuss side effects impacting on sexual health with service users are explored and emphasis is placed on the need for mental health nurses to respond to requests from service users for more education and discussion in the area of sexuality and sexual health.
Suicide: a literature review and its implications for nursing practice in Taiwan
Authors: SUN F.‐K. , LONG A. , BOORE J. , TSAO L.‐I.
Published: July 2005

In recent years the suicide rates have been increasing gradually in many countries. In order to reduce the number of suicides, further research on suicide and the nursing care of suicidal people is required to enhance and advance the quality of suicide nursing care provided. Statistical evidence shows that the most common method of completing suicide in many countries is hanging. Other evidence demonstrates that some suicides could be prevented if all patients were assessed for suicide risk and if psychiatric nurses provided effective nursing care, which centres on therapeutic communication skills. This paper explores the literature on suicide and on the nursing care of people who are suicidal, and also on the importance of integrating theory with practice.
Stepping out of the box: broadening the dialogue around the organizational implementation of cognitive behavioural psychotherapy
Authors: POOLE J. , GRANT A.
Published: July 2005

The dissemination and uptake of cognitive behavioural interventions is central to the evidence‐based mental health agenda in Britain. However, some policy and related literature, in and of itself social constructed, tends to display discursive naïvety in assuming a rational basis for the dissemination and organizational integration of cognitive behavioural approaches. Rational constructions fail to acknowledge that the practice settings of key stakeholders in the process are likely to be socially constructed fields of multiple meanings. Within these, the importance of evidence‐based interventions may be variously contested or reworked. To illustrate this, a case example from the first author will discuss the hypothetical introduction of a cognitive behavioural group for voice hearers in a forensic mental health unit. This will highlight contradictions and local organizational problems around the effective utilization of postgraduate cognitive behavioural knowledge and skills. A synthesis of social constructionist with organizational theory will be used to make better sense of these actual and anticipated difficulties. From this basis, specific ways in which nurses and supportive stakeholders could move the implementation of cognitive behavioural psychotherapy agenda forward within a postmodern leadership context will be proposed.
Constant or special observations of inpatients presenting a risk of aggression or violence: nurses’ perceptions of the rules of engagement
Authors: MACKAY I. , PATERSON B. , CASSELLS C.
Published: July 2005

In acute psychiatric settings the practice of ‘observation’ is commonly employed. Increased levels of observation, ‘constant’ or ‘special’ are used for those perceived as presenting a ‘higher’ risk. As an intervention it is used most frequently for those at risk of self‐harm or suicide, the practice is also however, used for those thought to present a risk of violent behaviour. In this descriptive study the perceptions of 1st level registered mental nurses (RMNs) gave an account of observation for those perceived to be at risk of violence or aggression and insight into what was considered important and desirable in practice. Unstructured qualitative interviews were conducted with a purposive sample of six RMNs from a psychiatric intensive care unit. Three major categories, Procedure, Role, and Skills emerged which revealed a complex practice far removed from its literal description as merely ‘watching’. Six subcategories emerged from the Role. (1) intervening; (2) maintaining the safety of the patient and others; (3) prevention de‐escalation and the management of aggression and violence; (4) assessing; (5) communication; and (6) therapy. Skills in these and, experience were thought to IMPACT on the success of the practice. The description of this and the skills involved offer a definition of the ‘rules of engagement’ which give insight to the practice and the training needs of staff advocated for ‘observation’. The acronym IMPACT may be useful in this.
Professional influences on the provision of mental health care for older people within a general hospital ward
Authors: HARRISON A. , ZOHHADI S.
Published: July 2005

Recent policy initiatives within the United Kingdom have recognized that effective care for older people can only be achieved if health care staff are willing and skilled enough to address patient needs in a holistic way. The preliminary stages of the action research project described here focused on the perceptions of nursing staff regarding the factors that impacted on their ability to address mental health needs within a general hospital ward. A phenomenological approach allowed us to identify the experience of addressing mental health needs in this setting from the perspective of the research participants. A focus group was facilitated with nursing staff whose primary professional focus was the provision of physical health care within an older adult unit. Thematic content analysis was used to analyse the focus group data, and four key themes emerged, namely ‘disruption’, ‘role conflict’, ‘professional resources’ and ‘professional distress’. These themes provide a focus for the ongoing development of the action research methods and will embed future work in the experience of those charged with ensuring that mental health care is a key element of their practice. This study highlights the urgent need for further work in this area, as we contend that it is only by addressing the professional needs of the staff concerned, that effective patient‐centred care can be ensured.
Implementing family intervention following training: what can the matter be?
Authors: MAIRS H. , BRADSHAW T.
Published: July 2005

Family interventions (FI) have been established as an effective treatment for psychosis. Training in this intervention is now widely available in the UK. This paper reports a review of published literature that investigates whether, following this training, graduates provide this evidence‐based treatment for individuals with psychosis and their caregivers. It further seeks to identify the barriers to implementation in cases where the treatment is not provided and assess benefits for service users and carers when it is. The review was conducted using the MEDline, PsycINFO, CINAHL and Embase databases. Studies that have attempted to evaluate the rates of implementation of FI by graduates of FI training programmes were identified, retrieved and reviewed. Six studies investigating the rates of implementation upon graduation were identified. The findings of these six studies were generally consistent. Rates of implementation by graduates of training programmes are usually low and a small number of graduates work with most of the families who are seen. The studies reviewed failed to assess service user and carer outcomes or consider the full range of likely impediments to the implementation of this evidence‐based intervention. A key barrier to the implementation of FI is the reliance upon professionally developed and facilitated approaches. Alternative models that are service user and carer‐led may provide a potential solution to the problem of implementation. Implications for future research and practice are considered
Responses of net ecosystem CO2 exchange in managed grassland to long‐term CO2 enrichment, N fertilization and plant species
Authors: AESCHLIMANN URS , NÖSBERGER JOSEF , EDWARDS PETER J. , SCHNEIDER MANUEL K. , RICHTER MICHAEL , BLUM HERBERT
Published: July 2005

The effects of elevated pCO2 on net ecosystem CO2 exchange were investigated in managed Lolium perenne (perennial ryegrass) and Trifolium repens (white clover) monocultures that had been exposed continuously to elevated pCO2 (60 Pa) for nine growing seasons using Free Air CO2 Enrichment (FACE) technology. Two levels of nitrogen (N) fertilization were applied. Midday net ecosystem CO2 exchange (mNEE) and night‐time ecosystem respiration (NER) were measured in three growing seasons using an open‐flow chamber system. The annual net ecosystem carbon (C) input resulting from the net CO2 fluxes was estimated for one growing season. In both monocultures and at both levels of N supply, elevated pCO2 stimulated mNEE by up to 32%, the exact amount depending on intercepted PAR. The response of mNEE to elevated pCO2 was larger than that of harvestable biomass. Elevated pCO2 increased NER by up to 39% in both species at both levels of N supply. NER, which was affected by mNEE of the preceding day, was higher in T. repens than in L. perenne. High N increased NER compared to low N supply. According to treatment, the annual net ecosystem C input ranged between 210 and 631 g C m−2 year−1 and was not significantly affected by the level of pCO2. Low N supply led to a higher net C input than high N supply. We demonstrated that at the ecosystem level, there was a long‐term stimulation in the net C assimilation during daytime by elevated pCO2. However, because NER was also stimulated, net ecosystem C input was not significantly increased at elevated pCO2. The annual net ecosystem C input was primarily affected by the amount of N supplied.
Stomatal, mesophyll conductance and biochemical limitations to photosynthesis as affected by drought and leaf ontogeny in ash and oak trees
Authors: GRASSI GIACOMO , MAGNANI FEDERICO
Published: July 2005

Gas exchange measurements were carried out on ash and oak trees in a forest plantation during three whole growing seasons characterized by different water availability (2001, 2002 and 2003). A quantitative limitation analysis was applied to estimate the effects of drought and leaf ontogeny on stomatal (SL) and non‐stomatal limitations (NSL) to light‐saturated net photosynthesis (Amax), relative to the seasonal maximum rates obtained under conditions of optimal soil water content. Furthermore, based on combined gas exchange and chlorophyll fluorescence measurements, NSL was partitioned into a diffusive (due to a decrease in mesophyll conductance, MCL) and a biochemical component (due to a decrease in carboxylation capacity, BL). During the wettest year (2002), the seasonal pattern of both Amax and stomatal conductance (gsw) was characterized in both species by a rapid increase during spring and a slight decline over the summer. However, with a moderate (year 2001) or a severe (year 2003) water stress, the summer decline of Amax and gsw was more pronounced and increased with drought intensity (30–40% in 2001, 60–75% in 2003). The limitation analysis showed that during the spring and the autumn periods SL, MCL and BL were of similar magnitude. By contrast, from the summer data it emerged that all the limitations increased with drought intensity, but their relative contribution changed. At mild to moderate water stress (corresponding to values of gsw > 100 mmol H2O m−2 s−1) about two‐thirds of the decline in Amax was attributable to SL. However, with increasing drought intensity, NSL increased more than SL and nearly equalled it when the stress was very severe (i.e. with gsw < 60 mmol H2O m−2 s−1). Within NSL, MCL represented the main component, except at the most severe water stress levels when it was equalled by BL. It is concluded that diffusional limitations (i.e. SL + MCL) largely affect net assimilation during most of the year, whereas biochemical limitations are quantitatively important only during leaf development and senescence or with severe droughts.
Expression of potassium‐transporter coding genes, and kinetics of rubidium uptake, along a longitudinal root axis
Authors: VALLEJO AUGUSTO J. , PERALTA MARIA LUISA , SANTA‐MARIA GUILLERMO E.
Published: July 2005

The pattern of mRNA accumulation of genes coding for the putative potassium transporters HvHAK1A, HvHAK1B, HvHAK2, HvHAK3 and HvAKT1 along seminal roots was studied in K+ starved barley (Hordeum vulgare) plants. Accumulation of these transcripts was lower in young, relative to older root zones, indicating the existence of a coordinated spatial pattern of gene regulation. A study of rubidium (Rb+) uptake kinetics showed that for all root zones transport can be dissected into a linear and a saturable component. Paralleling the pattern of mRNA accumulation the Vmax of the saturable term was lowest in the youngest root zone. No differences in the Rb+ Km or in the linear term were observed among root zones. K+ channel blockers Ba2+, Al3+, and tetraethylammonium exerted no effect on Rb+ uptake from diluted Rb+ solutions, while it was inhibited by Cs+, NH4+, methylamine, and K+ in all root zones. These results show that high‐affinity Rb+ transport over the entire axis is mediated by transporters displaying HAK1‐like properties. The observation of a differential effect of Na+ on Rb+ uptake along roots is compatible with a change in the proportion and/or the activity of those transport entities following a longitudinal gradient.
A mitochondrial half‐size ABC transporter is involved in cadmium tolerance in Chlamydomonas reinhardtii
Authors: HANIKENNE M. , MOTTE P. , WU M. C. S. , WANG T. , LOPPES R. , MATAGNE R. F.
Published: July 2005

Five cadmium‐sensitive insertional mutants, all affected at the CDS1 (‘cadmium‐sensitive 1’) locus, have been previously isolated in the unicellular green alga Chlamydomonas reinhardtii. We here describe the cloning of the Cds1 gene (8314 bp with 26 introns) and the corresponding cDNA. The Cds1 gene, strongly induced by cadmium, encodes a putative protein (CrCds1) of 1062 amino acid residues that belongs to the ATM/HMT subfamily of half‐size ABC transporters. This subfamily includes both vacuolar HMT‐type proteins transporting phytochelatin‐cadmium complexes from the cytoplasm to the vacuole and mitochondrial ATM‐type proteins involved in the maturation of cytosolic Fe/S proteins. Unlike the Δsphmt1 cadmium‐sensitive mutant of Schizosaccharomyces pombe that lacks a vacuolar HMT‐type transporter, the cds1 mutant accumulates a high amount of phytochelatin–cadmium complexes. By epitope tagging, the CrCds1 protein was localized in the mitochondria. Even though mitochondria of cds1 do not accumulate important amounts of ‘free’ iron, the mutant cells are hypersensitive to high iron concentrations. Our data show for the first time that a mitochondrial ATM‐like transporter plays a major role in tolerance to cadmium.
Differences in the success of sugar maple and red maple seedlings on acid soils are influenced by nutrient dynamics and light environment
Authors: ST CLAIR SAMUEL B. , LYNCH JONATHAN P.
Published: July 2005

Variation in tolerance to nutrient limitations may contribute to the differential success of sugar maple (Acer saccharum Marsh.) and red maple (Acer rubrum L.) on acid soils. The objectives of this study were to examine these relationships as influenced by light environment and test whether sensitivity to nutrient stress is mediated by oxidative stress. First‐year sugar maple and red seedlings were grown on forest soil cores contrasting in nutrient availability under high or low light intensity. Foliar nutrition, photosynthesis, growth and antioxidant enzyme activity were assessed. Photosynthesis and growth of sugar maple were significantly lower on nutrient‐poor soils and were correlated with leaf nutrient status with Ca and P having the strongest influence. For red maple, only chlorophyll content showed sensitivity to the nutrient‐poor soils. High light exacerbated the negative effects of nutrient imbalances on photosynthesis and growth in sugar maple. Antioxidant enzyme activity in sugar maple was highest in seedlings growing on nutrient‐poor soils and was inversely correlated with photosynthesis, Ca, P, and Mg concentrations. These results suggest that: (1) sugar maple is more sensitive to nutrient stresses associated with low pH soils than red maple; (2) high light increases sugar maple sensitivity to nutrient stress; (3) the negative effects of nutrient imbalances on sugar maple may be mediated by oxidative stress.
Temporal photosynthetic carbon isotope signatures revealed in a tree ring through 13CO2 pulse‐labelling
Authors: KAGAWA AKIRA , SUGIMOTO ATSUKO , YAMASHITA KANA , ABE HISASHI
Published: July 2005

Using a combined method of pulse‐labelling trees and analysing detailed distribution of 13C tracer within tree rings, we studied how photo‐assimilates incorporated on a given day are then distributed in a tree ring. A branch of a 4‐year‐old Cryptomeria japonica D.Don tree growing in Tsukuba, Japan was pulse‐labelled with non‐radioactive 13CO2 on two occasions: 29 May 2001 and 18 September 2001. Two discs were cut from the stem on 4 March 2002, one immediately under and the other 0.5 m below the branch and put through high‐resolution δ13C analysis. δ13C peaks were observed in both the earlywood and latewood of the concerned tree ring, corresponding to each pulse‐labelling date. The earlywood peaks was broader than the latewood peaks, possibly reflecting seasonal variation of the width of wood developing zone. Half‐widths of the peaks were measured and used as indicators for the potential time resolution of tree‐ring isotope analysis. The half‐widths of the peaks indicated a time resolution no finer than 8.7–28 and 33–42 d in the early and latewood, respectively. Holocellulose extraction yielded only a slight change to the shape of the δ13C peaks. 13C tracer pulse‐labelled in May and September reached tangentially different locations in the lower disc, suggesting a seasonal change in the pathway of carbohydrates. Local consumption of spring assimilates and long‐distance downward transport of autumn assimilates were also suggested.
Leaf anatomy as a constraint for photosynthetic acclimation: differential responses in leaf anatomy to increasing growth irradiance among three deciduous trees
Authors: OGUCHI R. , HIKOSAKA K. , HIROSE T.
Published: July 2005

Interspecific variation in the response to transfer from low to high growth irradiance with respect to anatomical and photosynthetic characteristics was studied in mature leaves of three tree species, Betula ermanii Cham., Acer rufinerve Sieb. et Zucc. and Fagus crenata Blume, which occur in different successional stages in temperate deciduous forests. Transfer from low to high irradiance increased the light‐saturated rate of photosynthesis per unit leaf area (Pmax) significantly in B. ermanii and A. rufinerve, but not in F. crenata. Leaves of B. ermanii grown at low irradiance were relatively thick and had vacant spaces along the mesophyll cell surfaces which was not occupied by chloroplasts or other organelles. After transfer to high irradiance, chloroplasts enlarged to fill the space along with Pmax without an increase in leaf thickness. Leaves of A. rufinerve were plastic in mesophyll cell surface area and in leaf thickness, both of which increased after the transfer to high irradiance, along with an increase in the amount of chloroplasts and in Pmax. On the other hand, F. crenata had little mesophyll cell surface unoccupied by chloroplasts and leaf anatomy was not changed after the transfer. In all species, Pmax was strongly correlated with chloroplast surface area adjacent to the exposed mesophyll surface across different growth irradiances. An increase in Pmax was observed only when chloroplast volume also increased. We conclude that light acclimation potential is primarily determined by the availability of unoccupied cell surface into which chloroplasts expand, as well as by the plasticity of the mesophyll that allows an increase in its surface area.
Contrasting phosphate acquisition of mycorrhizal fungi with that of root hairs using the root hairless barley mutant
Authors: JAKOBSEN IVER , CHEN BAODONG , MUNKVOLD LISA , LUNDSGAARD THORBEN , ZHU YONG‐GUAN
Published: July 2005

Comparisons between plant species or cultivars differing in root hair length have indicated a major impact of root hairs on the mycorrhizal dependency of plants with respect to phosphate (P) uptake. The current study aimed to investigate this relationship by comparing directly the mycorrhizal dependency of a spontaneous root hairless mutant, brb, in Hordeum vulgare cv Pallas and its wild type. Both brb and wild type were grown at different soil P levels in association with different mycorrhizal fungi. P uptake of brb and wild type was similar at high P levels, but P uptake by non‐mycorrhizal brb plants at low P levels was substantially lower than that of the non‐mycorrhizal wild‐type plants. However, P uptake of the mutant was much increased by mycorrhizas and with one fungus, the additional P uptake was effectively translated into increased plant growth. Roots of the mutant contained typical colonization structures and a radioactive tracer confirmed P transport by the extraradical mycelium. This is the first direct evaluation of the relative effectiveness of root hairs and mycorrhizas. Mycorrhizas effectively substituted root hairs in P uptake, whereas the additional P was most often used less effectively in promoting plant growth than P provided by root hairs.
Behaviour and dynamics of a hydrothermal plume in Lake Banyoles, Catalonia, NE Spain
Authors: SERRA TERESA , SOLER MARIANNA , JULIÀ RAMON , CASAMITJANA XAVIER , COLOMER JORDI
Published: July 2005

A hydrothermal plume forms in Lake Banyoles, NE Spain, as a result of convection above a springwater‐fed suspension cloud ponded on the lake floor. The plume propagates upwards reaching a level of neutral buoyancy from where a turbidity current spreads out laterally. Two‐dimensional temperature and particle concentration measurements show the fate of the hydrothermal plume and its associated turbidity current and reveal its seasonal development. Silt particles transported by the plume have been used as tracers to determine the maximum and equilibrium heights of the plume. When the lake is stratified, the vertical transport of sediment is confined to the lake hypolimnion, as the thermocline limits the vertical propagation of the plume. In contrast, when the lake water column is mixed, the plume reaches the surface of the lake. The field measurements have been compared with models for thermal convection from finite isolated sources. Measurements of the flow velocity at the source of the hydrothermal plume (i.e. the rim current velocity) indicate that cold hypolimnetic water is entrained by the plume. Sedimentation rates measured from sediment traps at the zone where the turbidity current develops vary between 10 and 25 g m−2 day−1, and result from continuous silt particle sedimentation from the turbidity current. Sedimentation rates in traps are higher for stations situated close to the source than those further away (<5 g m−2 day−1). Moreover, the results demonstrate that double diffusive sedimentation from the turbidity current was dominant over grain‐by‐grain settling, causing a mixed distribution of sediments in the region where the turbidity current spreads. The deposition of silt particles could explain the occurrence of silt layers interbedded with biocalcarenites in the littoral zones of the lake and the stratigraphy identified by seismic profiles and cores taken from the lake floor.
Sand grain threshold, in relation to bed ‘stress history’: an experimental study
Authors: PAPHITIS D. , COLLINS M. B.
Published: July 2005

Besides particle size, density and shape, the erodibility of a sediment bed depends also upon the exposure to prethreshold velocities in the overlying flow. Such flow effectively rearranges the grains (at and below the bed surface), causing them to become more resistant to subsequent erosion. The effects of the ‘stress history’, leading up to the critical condition for sediment movement, are investigated for unidirectional flows generated in a recirculating laboratory flume. The sediment beds investigated consisted of cohesionless quartz sand grains, with mean grain diameters of 0·194 mm (fine sand), 0·387 mm (medium sand) and 0·774 mm (coarse sand), with narrow particle‐size distributions. The critical (threshold) shear velocity (target value) for the three beds was established, within 2·5 min of increasing the flow from zero velocity. The subsequent experiments were performed under prethreshold velocities at 70% (for 5, 10, 20, 40 and 80 min exposure duration), 80% (for 5, 10, 20, 40 and 80 min exposure duration), 90 and 95% (for 5, 10, 20, 40, 80 and 120 min exposure duration) of the target value. Following exposure to these different prethreshold conditions, the flow was increased then to reach actual critical conditions, within a period of 2·5 min. The critical condition for the initiation of sediment movement was established using visual observation (supplemented by video recordings), according to the Yalin criterion. The results show that if the exposure duration to prethreshold velocities remains constant, then the critical shear velocity increases with increasing prethreshold velocity. Likewise, if the prethreshold velocity remains constant, then the critical shear velocity increases with increasing exposure duration. In some circumstances, the critical shear velocity was found to increase by as much as 27%. An empirical formula is proposed to account for the exposure correction to be applied to the critical shear velocities of sand‐sized sediment beds; this is prior to their inclusion into bedload transport formulae, for an improved prediction of the magnitude and nature of transport.
Bedload path length and point bar development in gravel‐bed river models
Authors: PYRCE RICHARD S. , ASHMORE PETER E.
Published: July 2005

Low‐sinuosity meandering gravel‐bed flume experiments were employed to investigate spatial patterns of deposition, which point to patterns of channel development related to the pool and bar morphology. At channel‐forming discharges, fluorescent bedload tracers indicate that deposition is typically focused around the point bar apex, downstream of the apex (contributing to downstream bar migration), and at the bar head/riffle surface. Seven flume experimental runs illustrate a sequence of point bar development related to the spatial patterns of tracer deposition, and the related path length distribution. At early stages of bar formation, transport is from the scour zone across the point bar head to the bar apex and bar margin downstream of the apex. As the point bar develops, bedload transport across the bar decreases, as transport along the channel thalweg increases and sediment is deposited along the bar margin. Deposition cells appear to move from downstream to upstream of the bar apex as this sequence of bar formation progresses. At low (non‐channel‐forming) discharges, transport occurs to the bar head/riffle surface with very little material being transported to the apex region or point bar interior. The implication is that there is an inherent connection between the loci of particle deposition and point bar formation, largely controlled by the morphology of the channel.
Pre‐vegetation alluvial fan facies and processes: an example from the Cambro‐Ordovician Rozel Conglomerate Formation, Jersey, Channel Islands
Authors: WENT DAVID J.
Published: July 2005

Prior to the Silurian a lack of land vegetation is expected to have influenced the processes of sedimentation on alluvial fans, principally by causing increased rates of run‐off and erosion in the fan catchments. In the Cambro‐Ordovician Rozel Conglomerate Formation, this effect was central to the generation of alluvial fan deposits that are unusually deficient in sand and clay, despite being sourced from a catchment dominated by sandstone and mudstone. Seven facies are identified, interpreted as representing the deposits of: (i) shallow stream and sheetfloods, (ii) channelized, non‐cohesive debrisflows, (iii) sub‐aerial mud‐rich debrisflows, (iv) sub‐aqueous mud‐rich debrisflows, (v) low energy streams that reworked abandoned fan sectors, (vi) a sandflat‐playa lake system and (vii) talus slopes. The first two facies are both clast‐supported conglomerate, comprise 98% of the deposit, and represent deposition on active depositional lobes and in the fan head trench. The remaining facies are the products of infrequent sedimentary processes, fan abandonment processes and marginal sub‐environments. The facies assemblage in many ways mimics that of a modern‐day, water‐lain, arid region fan. However, the palaeolatitude of these fans was high and the climate is inferred to have been cool and wet. The near absence of sandstone and mudstone beds with few mudflows is ascribed to rapid hinterland uplift and high rates of erosion resulting in minimal chemical breakdown of source rocks in the catchments. Such high rates of erosion are in turn ascribed to a combination of frequent rainstorms and an absence of vegetation cover.