Pattern of extinction of the woolly mammoth in Beringia.

Extinction of the woolly mammoth in Beringia has long been subject to research and speculation. Here we use a new geo-referenced database of radiocarbon-dated evidence to show that mammoths were abundant in the open-habitat of Marine Isotope Stage 3 (∼45-30 ka). During the Last Glacial Maximum (∼25-20 ka), northern populations declined while those in interior Siberia increased. Northern mammoths increased after the glacial maximum, but declined at and after the Younger Dryas (∼12.9-11.5 ka). Remaining continental mammoths, now concentrated in the north, disappeared in the early Holocene with development of extensive peatlands, wet tundra, birch shrubland and coniferous forest. Long sympatry in Siberia suggests that humans may be best seen as a synergistic cofactor in that extirpation. The extinction of island populations occurred at ∼4 ka. Mammoth extinction was not due to a single cause, but followed a long trajectory in concert with changes in climate, habitat and human presence.

Global warming and the Arctic: a new world beyond the reach of the Grinnellian niche?

The levels of CO(2) in the atmosphere have already far exceeded values attained at any other time over at least the past 650,000 years. Temperature increases due to rising greenhouse gases will be amplified in Arctic and subarctic regions, and winter warming will be enhanced relative to summer warming. Climate in large areas of high latitudes may have no analogue in current climates or those of the recent geological past. Experimental field manipulations and laboratory studies indicate that plants will exhibit complex responses in photosynthesis, growth rates, phenology and reproductive functioning due to this combination of increasing temperatures, changing seasonality and increasing levels of CO(2). The resulting changes in the abundance, distribution, growth rates and production of fruit and phenology of plant species will in turn impact animal populations. In predicting what the future biota of the 'New Arctic' will be like and developing appropriate conservation strategies, Grinnellian niche-based approaches are likely to be insufficient, and experimental ecological studies of organism response to specific anticipated changes in climate are crucial.

WITHDRAWN: Home-based support for disadvantaged adult mothers.

BACKGROUND: Babies born to socio-economically disadvantaged mothers are at higher risk of a range of problems in infancy. Home visiting programs are thought to improve outcomes, both for mothers and children, largely through advice and support. OBJECTIVES: To assess the effectiveness of home visiting programmes for women who have recently given birth and who are socially or economically disadvantaged. SEARCH STRATEGY: We searched the following electronic databases: The Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 3, 2006); MEDLINE (1966 to March 2006); EMBASE (1980 to 2006 week 12); CINAHL (1982 to March week 4 2006); PsycINFO (1872 to March week 4 2006); ASSIA (1987 to March 2006); LILACS (1982 to March 2006); and Sociological Abstracts(1963 to March 2006). We searched grey literature using ZETOC (1993 to March 2006); Dissertation Abstracts International (late 1960s to 2006); and SIGLE (1980 to March 2006). We also undertook communication with published authors about ongoing or unpublished research. SELECTION CRITERIA: Included studies were randomised controlled trials investigating the efficacy of home visiting directed at disadvantaged adult mothers. DATA COLLECTION AND ANALYSIS: Two reviewers (EC and JP or CB) independently assessed titles and abstracts identified in the search for eligibility. Data were extracted and entered into RevMan (EC, JP and CB), synthesised and presented in both written and graphical form (forest plots). Outcomes included in this review were established at the protocol stage by an international steering group. The review does not report on all outcomes reported in included studies. MAIN RESULTS: We included 11 studies with 4751 participants in this review. Data show no statistically significant differences for those receiving home visiting, either for maternal outcomes (maternal depression, anxiety, the stress associated with parenting, parenting skills, child abuse risk or potential or breastfeeding) or child outcomes (preventive health care visits, psychosocial health, language development, behaviour problems or accidental injuries. Evidence about uptake of immunisations is mixed, and the data on child maltreatment difficult to interpret. AUTHORS' CONCLUSIONS: This review suggests that for disadvantaged adult women and their children, there is currently no evidence to support the adoption of home visiting as a means of improving maternal psychosocial health, parenting or outcomes for children. For reasons discussed in the review, this does not amount to a conclusion that home visiting programmes are ineffective, but indicates a need to think carefully about the problems that home visiting might influence, and improvements in the conduct of outcome studies in this area.

Treatment foster care for improving outcomes in children and young people.

BACKGROUND: Treatment foster care (TFC) is a foster family-based intervention that aims to provide young people (and, where appropriate, their families) with a tailored programme designed to effect positive changes in their lives. TFC was designed specifically to cater for the needs of children whose difficulties or circumstances place them at risk of multiple placements and/or more restrictive placements such as hospital or secure residential or youth justice settings. OBJECTIVES: To assess the impact of TFC on psychosocial and behavioural outcomes, delinquency, placement stability, and discharge status for children and adolescents who require out-of-home placement. SEARCH STRATEGY: We searched the Cochrane Controlled Trials Register (CENTRAL) 2006 (Issue 4), MEDLINE (1966 to January 2007), CINAHL (1982 to December 2006), PsycINFO (1872 to January 2007), ASSIA (1987 to January 2007), LILACS (1982 to January 2007), ERIC (1966 to January 2007), Sociological Abstracts (1963 to January 2007), and the National Research Register 2006 (Issue 4). SELECTION CRITERIA: Included studies were randomised controlled trials investigating the effectiveness of TFC with children and young people up to the age of 18 who, for reasons of severe medical, social, psychological and behavioural problems, were placed in out of home care in restrictive settings (e.g. secure residential care, psychiatric hospital) or at risk of placement in such settings. DATA COLLECTION AND ANALYSIS: Titles and abstracts identified in the search were independently assessed for eligibility by the two authors (GM and WT) who also extracted and entered into REVMAN. Date were synthesised on the few occasions where this was possible. Results are presented in tabular, graphical (forest plots) and textual form. MAIN RESULTS: Five studies including 390 participants were included in this review. Data suggest that treatment foster care may be a useful intervention for children and young people with complex emotional, psychological and behavioural need, who are at risk of placements in non-family settings that restrict their liberty and opportunities for social inclusion. AUTHORS' CONCLUSIONS: Although the inclusion criteria for this systematic review set a study design threshold higher than that of previous reviews, the results mirror those of earlier reviews but also highlights the tendency of the perceived effectiveness of popular interventions to outstrip their evidence base. Whilst the results of individual studies generally indicate that TFC is a promising intervention for children and youth experiencing mental health problems, behavioural problems or problems of delinquency, the evidence base is less robust than that usually reported.

Climate change and the northern Russian treeline zone.

The Russian treeline is a dynamic ecotone typified by steep gradients in summer temperature and regionally variable gradients in albedo and heat flux. The location of the treeline is largely controlled by summer temperatures and growing season length. Temperatures have responded strongly to twentieth-century global warming and will display a magnified response to future warming. Dendroecological studies indicate enhanced conifer recruitment during the twentieth century. However, conifers have not yet recolonized many areas where trees were present during the Medieval Warm period (ca AD 800-1,300) or the Holocene Thermal Maximum (HTM; ca 10,000-3,000 years ago). Reconstruction of tree distributions during the HTM suggests that the future position of the treeline due to global warming may approximate its former Holocene maximum position. An increased dominance of evergreen tree species in the northern Siberian forests may be an important difference between past and future conditions. Based on the slow rates of treeline expansion observed during the twentieth century, the presence of steep climatic gradients associated with the current Arctic coastline and the prevalence of organic soils, it is possible that rates of treeline expansion will be regionally variable and transient forest communities with species abundances different from today's may develop.

Home-based support for disadvantaged adult mothers.

BACKGROUND: Babies born to socio-economically disadvantaged mothers are at higher risk of a range of problems in infancy. Home visiting programs are thought to improve outcomes, both for mothers and children, largely through advice and support. OBJECTIVES: To assess the effectiveness of home visiting programmes for women who have recently given birth and who are socially or economically disadvantaged. SEARCH STRATEGY: We searched the following electronic databases: The Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 3, 2006); MEDLINE (1966 to March 2006); EMBASE (1980 to 2006 week 12); CINAHL (1982 to March week 4 2006); PsycINFO (1872 to March week 4 2006); ASSIA (1987 to March 2006); LILACS (1982 to March 2006); and Sociological Abstracts(1963 to March 2006). We searched grey literature using ZETOC (1993 to March 2006); Dissertation Abstracts International (late 1960s to 2006); and SIGLE (1980 to March 2006). We also undertook communication with published authors about ongoing or unpublished research. SELECTION CRITERIA: Included studies were randomised controlled trials investigating the efficacy of home visiting directed at disadvantaged adult mothers. DATA COLLECTION AND ANALYSIS: Two reviewers (EC and JP or CB) independently assessed titles and abstracts identified in the search for eligibility. Data were extracted and entered into RevMan (EC, JP and CB), synthesised and presented in both written and graphical form (forest plots). Outcomes included in this review were established at the protocol stage by an international steering group. The review does not report on all outcomes reported in included studies. MAIN RESULTS: We included 11 studies with 4751 participants in this review. Data show no statistically significant differences for those receiving home visiting, either for maternal outcomes (maternal depression, anxiety, the stress associated with parenting, parenting skills, child abuse risk or potential or breastfeeding) or child outcomes (preventive health care visits, psychosocial health, language development, behaviour problems or accidental injuries. Evidence about uptake of immunisations is mixed, and the data on child maltreatment difficult to interpret. AUTHORS' CONCLUSIONS: This review suggests that for disadvantaged adult women and their children, there is currently no evidence to support the adoption of home visiting as a means of improving maternal psychosocial health, parenting or outcomes for children. For reasons discussed in the review, this does not amount to a conclusion that home visiting programmes are ineffective, but indicates a need to think carefully about the problems that home visiting might influence, and improvements in the conduct of outcome studies in this area.

Cognitive-behavioural training interventions for assisting foster carers in the management of difficult behaviour.

BACKGROUND: The provision of training for foster carers is now seen as an important factor contributing to the successful outcome of foster care placements. Since the late 1960s, foster carer training programs have proliferated, and few of the many published and unpublished training curricula have been systematically assessed and evaluated. The advent of cognitive-behavioural therapy (CBT) and the research evidence demonstrating its effectiveness as a psychotherapeutic treatment of choice, has prompted many working in the social care field to devise CBT-based training programmes. CBT approaches to foster care training derive from a 'skill-based' training format that also seeks to identify and correct problematic thinking patterns that are associated with dysfunctional behaviour by changing and/or challenging maladaptive thoughts and beliefs. OBJECTIVES: To assess the effectiveness of cognitive-behavioural training interventions in improving a) looked-after children's behavioural/relationship problems, b) foster carers' psychological well-being and functioning, c) foster family functioning, d) foster agency outcomes. SEARCH STRATEGY: We searched databases including: CENTRAL (Cochrane Library Issue 3, 2006), MEDLINE (January 1966 to September 2006), EMBASE (January 1980 to April 2004), CINAHL (January 1982 to April 2004), PsycINFO (January 1872 to April 2004), ASSIA (January 1987 to April 2004), LILACS (up to April 2004), ERIC (January 1965 to April 2004), Sociological Abstracts (January 1963 to April 2004), and the National Research Register 2004 (Issue 3). We contacted experts in the field concerning current research. SELECTION CRITERIA: All studies in which participants were foster parents/carers, and who were allocated by random or quasi-random methods to a CBT-based training intervention (in a group and/or one-to-one settings) versus a no-treatment or wait-list control, were selected. DATA COLLECTION AND ANALYSIS: Data from the six eligible trials (total n = 463 ) were extracted and entered into RevMan. Results were synthesised and presented in both graphical (forest plots) and narrative form (where insufficient data were provided for effect size computations). MAIN RESULTS: Training interventions evaluated to date appear to have very little effect on outcomes relating to looked-after children, assessed in relation to psychological functioning, extent of behavioural problems and interpersonal functioning. Results relating to foster carer(s) outcomes also show no evidence of effectiveness in measures of behavioural management skills, attitudes and psychological functioning. Analysis pertaining to fostering agency outcomes did not show any significant results. AUTHORS' CONCLUSIONS: There is currently little evidence about the efficacy of CBT-based training intervention for foster carers. The need for further research in this area is highlighted.

Supported housing for people with severe mental disorders.

BACKGROUND: There has been a significant reduction in the number of people with severe mental illness who spend extended periods in long-stay hospitals. District health authorities, local authorities, housing associations and voluntary organisations are jointly expected to provide support for people with severe mental disorder/s. This 'support' may well involve some kind of special housing. OBJECTIVES: To determine the effects of supported housing schemes compared with outreach support schemes or 'standard care' for people with severe mental disorder/s living in the community. SEARCH STRATEGY: For the 2006 update we searched the Cochrane Schizophrenia Group Trials Register (April 2006) and the Cochrane Central Register of Controlled Trials (CENTRAL, 2006 Issue 2). SELECTION CRITERIA: We included all relevant randomised, or quasi-randomised, trials dealing with people with 'severe mental disorder/s' allocated to supported housing, compared with outreach support schemes or standard care. We focused on outcomes of service utilisation, mental state, satisfaction with care, social functioning, quality of life and economic data. DATA COLLECTION AND ANALYSIS: We reliably selected studies, quality rated them and undertook data extraction. For dichotomous data, we would have estimated relative risks (RR), with the 95% confidence intervals (CI). Where possible, we would have calculated the number needed to treat statistic (NNT). We would have carried out analysis by intention-to-treat and would have summated normal continuous data using the weighted mean difference (WMD). We would have presented scale data for only those tools that had attained pre-specified levels of quality and undertaken tests for heterogeneity and publication bias. MAIN RESULTS: Although 139 citations were acquired from the searches, no study met the inclusion criteria. AUTHORS' CONCLUSIONS: Dedicated schemes whereby people with severe mental illness are located within one site or building with assistance from professional workers have potential for great benefit as they provide a 'safe haven' for people in need of stability and support. This, however, may be at the risk of increasing dependence on professionals and prolonging exclusion from the community. Whether or not the benefits outweigh the risks can only be a matter of opinion in the absence of reliable evidence. There is an urgent need to investigate the effects of supported housing on people with severe mental illness within a randomised trial.

Cognitive-behavioural interventions for children who have been sexually abused.

BACKGROUND: Despite differences in perceptions of what constitutes child sexual abuse there is a general consensus amongst clinicians and researchers that this is a substantial social problem which affects large numbers of children and young people worldwide. The effects of sexual abuse manifest themselves in a wide range of symptoms, including fear, anxiety, post-traumatic stress disorder and behaviour problems such as externalising or internalising, or inappropriate sexual behaviours. Child sexual abuse is associated with increased risk of psychological problems in adulthood. Knowing what is most likely to benefit children already traumatised by these events is important. OBJECTIVES: The aim of this review was to assess the efficacy of cognitive-behavioural approaches (CBT) in addressing the immediate and longer-term sequelae on children who have been sexually abused. SEARCH STRATEGY: The Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 5, 2005), MEDLINE (1966-November 2005); EMBASE (1980-November 2005); CINAHL (1982-November 2005), PsycINFO (1897-November 2005); LILACS (1982-November 2005); SIGLE (1980 to November 2005) and the register of the Cochrane Developmental, Psychosocial and Learning Problems Group (November 2005) were searched. SELECTION CRITERIA: Included studies were randomised or quasi-randomised controlled trials investigating the efficacy of cognitive behavioural therapy on children and adolescents up to age 18 years who had experienced sexual abuse. DATA COLLECTION AND ANALYSIS: Titles and abstracts identified in the search were independently assessed for eligibility by two reviewers (GM and PR). Data were extracted and entered into REVMAN (JH and GM), and synthesised and presented in both written and graphical form (forest plots). MAIN RESULTS: Ten trials, including 847 participants, were included in this review. Data suggest that CBT may have a positive impact on the sequelae of child sexual abuse, but most results were statistically non-significant. AUTHORS' CONCLUSIONS: The review confirms CBT's potential as a means of addressing the adverse consequences of child sexual abuse, but highlights the tenuousness of the evidence base and the need for more carefully conducted and better reported trials.

Disappearing Arctic lakes.

Historical archived satellite images were compared with contemporary satellite data to track ongoing changes in more than 10,000 large lakes in rapidly warming Siberia. A widespread decline in lake abundance and area has occurred since 1973, despite slight precipitation increases to the region. The spatial pattern of lake disappearance suggests (i) that thaw and "breaching" of permafrost is driving the observed losses, by enabling rapid lake draining into the subsurface; and (ii) a conceptual model in which high-latitude warming of permafrost triggers an initial but transitory phase of lake and wetland expansion, followed by their widespread disappearance.

Cognitive-behavioural training interventions for assisting foster carers in the management of difficult behaviour.

BACKGROUND: The provision of training for foster carers is now seen as an important factor contributing to the successful outcome of foster care placements. It is believed to be associated with enhancing caring attitudes and skills, reducing behaviour problems in foster children, improving relationships between foster carers and child welfare agencies, and decreasing foster carer attrition. Since the late 1960s, foster carer training programs have proliferated, and few of the many published and unpublished training curricula have been systematically assessed and evaluated. The advent of cognitive-behavioural therapy (CBT) and the research evidence demonstrating its effectiveness as a psychotherapeutic treatment of choice, has prompted many working in the social care field to devise CBT-based training programmes. CBT approaches to foster care training derive from a 'skill-based' training format that also seeks to identify and correct problematic thinking patterns that are associated with dysfunctional behaviour by changing and/or challenging maladaptive thoughts and beliefs. OBJECTIVES: To assess the effectiveness of cognitive-behavioural training interventions in improving a) looked-after children's behavioural/relationship problems, b) foster carers' psychological well-being and functioning, c) foster family functioning, d) foster agency outcomes. SEARCH STRATEGY: We searched databases including: CENTRAL (Cochrane Library Issue 2, 2004), MEDLINE (January 1966 to April 2004), EMBASE (January 1980 to April 2004), CINAHL (January 1982 to April 2004), PsycINFO (January 1872 to April 2004), ASSIA (January 1987 to April 2004), LILACS (up to April 2004), ERIC (January 1965 to April 2004), Sociological Abstracts (January 1963 to April 2004), and the National Research Register 2004 (Issue 1). We contacted experts in the field concerning current research. SELECTION CRITERIA: All studies in which participants were foster parents/carers, and who were allocated by random or quasi-random methods to a CBT-based training intervention (in a group and/or one-to-one settings) versus a no-treatment or wait-list control, were selected. DATA COLLECTION AND ANALYSIS: Results from the five eligible trials (total n = 443 ) are reported narratively. Due to the diversity of measures employed, no meta-analysis was performed. MAIN RESULTS: Training interventions evaluated to date appear to have very little effect on outcomes relating to looked-after children, assessed in relation to psychological functioning, extent of behavioural problems and interpersonal functioning. Results relating to foster carer(s) outcomes indicate some improvements in measures of behavioural management skills, attitudes and psychological functioning. Analysis pertaining to fostering agency outcomes did not show any significant results. AUTHORS' CONCLUSIONS: Inconclusive evidence exists about the efficacy of CBT-based training intervention for foster carers. The need for further research in this area is highlighted.

Siberian peatlands a net carbon sink and global methane source since the early Holocene.

Interpolar methane gradient (IPG) data from ice cores suggest the "switching on" of a major Northern Hemisphere methane source in the early Holocene. Extensive data from Russia's West Siberian Lowland show (i) explosive, widespread peatland establishment between 11.5 and 9 thousand years ago, predating comparable development in North America and synchronous with increased atmospheric methane concentrations and IPGs, (ii) larger carbon stocks than previously thought (70.2 Petagrams, up to approximately 26% of all terrestrial carbon accumulated since the Last Glacial Maximum), and (iii) little evidence for catastrophic oxidation, suggesting the region represents a long-term carbon dioxide sink and global methane source since the early Holocene.

Supported housing for people with severe mental disorders.

BACKGROUND: There has been a significant reduction in the number of people with severe mental illness who spend extended periods in long-stay hospitals. Psychiatric and social services, both statutory and voluntary, aim to assist these people to stay in their local community. District health authorities, local authorities, housing associations and voluntary organisations are jointly expected to provide support for people with severe mental disorder/s. This 'support' may well involve some sort of special housing. OBJECTIVES: To determine the effects of supported housing schemes compared with outreach support schemes or 'standard care' for people with severe mental disorder/s living in the community. SEARCH STRATEGY: Cochrane Schizophrenia Group's Register of trials (February 2001) and the Cochrane Library (Issue 1, 2001) were searched using relevant phrases. These databases are compiled by methodical searches of BIOSIS, CINAHL, Dissertation abstracts, EMBASE, LILACS, MEDLINE, PSYNDEX, PsycINFO, RUSSMED, Sociofile, supplemented with hand searching of relevant journals and numerous conference proceedings. Reference list screening of relevant papers was performed. SELECTION CRITERIA: Relevant randomised, or quasi-randomised, trials dealing with people with 'severe mental disorder/s' allocated to supported housing, outreach support schemes or standard care focusing on outcomes of service utilisation, mental state, satisfaction with care, social functioning, quality of life, and economic data, were sought. DATA COLLECTION AND ANALYSIS: Studies were reliably selected, quality rated and data extracted. For dichotomous data, relative risks (RR) would have been estimated, with the 95% confidence intervals (CI). Where possible, the number needed to treat statistic (NNT) was to have been calculated. Analysis would have been by intention-to-treat. Normal continuous data were to have been summated using the weighted mean difference (WMD). Scale data were to have been presented for only those tools that had attained pre-specified levels of quality. Tests of heterogeneity and for publication bias were to have been undertaken. MAIN RESULTS: No studies met the inclusion criteria although 139 citations were acquired from the searches. REVIEWER'S CONCLUSIONS: Dedicated schemes whereby people with severe mental illness are located within one site or building with assistance from professional workers have potential for great benefit as they provide a 'safe haven' for people in need of stability and support. This, however, may be at the risk of increasing dependence on professionals and prolonging exclusion from the community. Whether or not the benefits outweigh the risks can only be a matter of opinion in the absence of reliable evidence. There is an urgent need to investigate the effects of supported housing on people with severe mental illness within a randomised trial.

Supported housing for people with severe mental disorders.

BACKGROUND: There has been a significant reduction in the number of people with severe mental illness who spend extended periods in long-stay hospitals. Psychiatric and social services, both statutory and voluntary, aim to assist these people to stay in their local community. District health authorities, local authorities, housing associations and voluntary organisations are jointly expected to provide support for people with severe mental disorder/s. This 'support' may well involve some sort of special housing. OBJECTIVES: To determine the effects of supported housing schemes compared with outreach support schemes or 'standard care' for people with severe mental disorder/s living in the community. SEARCH STRATEGY: Cochrane Schizophrenia Group's Register of trials (February 2001) and the Cochrane Library (Issue 1, 2001) were searched using relevant phrases. These databases are compiled by methodical searches of BIOSIS, CINAHL, Dissertation abstracts, EMBASE, LILACS, MEDLINE, PSYNDEX, PsycINFO, RUSSMED, Sociofile, supplemented with hand searching of relevant journals and numerous conference proceedings. Reference list screening of relevant papers was performed. SELECTION CRITERIA: Relevant randomised, or quasi-randomised, trials dealing with people with 'severe mental disorder/s' allocated to supported housing, outreach support schemes or standard care focusing on outcomes of service utilisation, mental state, satisfaction with care, social functioning, quality of life, and economic data, were sought. DATA COLLECTION AND ANALYSIS: Studies were reliably selected, quality rated and data extracted. For dichotomous data, relative risks (RR) would have been estimated, with the 95% confidence intervals (CI). Where possible, the number needed to treat statistic (NNT) was to have been calculated. Analysis would have been by intention-to-treat. Normal continuous data were to have been summated using the weighted mean difference (WMD). Scale data were to have been presented for only those tools that had attained pre-specified levels of quality. Tests of heterogeneity and for publication bias were to have been undertaken. MAIN RESULTS: No studies met the inclusion criteria although 139 citations were acquired from the searches. REVIEWER'S CONCLUSIONS: Dedicated schemes whereby people with severe mental illness are located within one site or building with assistance from professional workers have potential for great benefit as they provide a 'safe haven' for people in need of stability and support. This, however, may be at the risk of increasing dependence on professionals and prolonging exclusion from the community. Whether or not the benefits outweigh the risks can only be a matter of opinion in the absence of reliable evidence. There is an urgent need to investigate the effects of supported housing on people with severe mental illness within a randomised trial.

Modern pollen and stomate deposition in lake surface sediments from across the treeline on the Kola Peninsula, Russia.

We sampled and analyzed surface sediments from 31 lakes along a latitudinal transect crossing the coniferous treeline on the Kola Peninsula, Russia. The major vegetation zones along the transect were tundra, birch-forest tundra, pine-forest tundra, and forest. The results indicate that the major vegetation types in our study area have distinct pollen spectra. Sum-of-squares cluster analysis and principal components analysis (PCA) groupings of pollen sites correspond to the major vegetation zones. PCA ordination of taxa indicates that the first axis separates taxa typical of the forest zone (Pinus, Picea) from taxa typical of tundra and forest-tundra zones (Polypodiaceae, Ericaceae, and Betula). The current position of the coniferous treeline, defined in our region by Pinus sylvestris, occurs roughly where Pinus pollen values reach 35% or greater. Arboreal pollen (AP)/non-arboreal pollen (NAP) ratios were calculated for each site and plotted against geographic distance along the transect. AP/NAP ratios of 7 or greater are found within pine-forest tundra and forest vegetation zones. Pinus stomates (dispersed stomatal guard cells) are absent from sites north of the coniferous treeline and all but two samples from the forested sites contain stomates. Stomate concentrations among the samples are highly variable and range from 10 to 458 per ml and positively correlate with the changing Pinus pollen values.

Dedicated short-stay spinal unit.

Prolonged waiting periods for patients with benign spinal surgical lesions led to the creation of a Dedicated Short Stay Spinal Surgical Unit. This unit was implemented in November, 1992, on a 29 bed Neuroscience Unit in a 1200 bed Acute Care Teaching Hospital. Considerations for implementation were many, including psychological impact of chronic pain for patients on prolonged waiting lists, the increased probability of permanent waiting lists, the increased probability of permanent neurological deficits, and the economic impact to patient, societal and hospital budgets. This paper will focus on explanation of the design of the unit, define the benefits and provide study results of the first 85 patients admitted to the unit.

A difference Fourier transform infrared spectroscopic study of chlorophyll oxidation in hydroxylamine-treated photosystem II.

In oxygenic photosynthesis, photosystem II is the chlorophyll-containing reaction center that carries out the light-induced transfer of electrons from water to plastoquinone. Fourier transform infrared spectroscopy can be used to obtain information about the structural changes that accompany electron transfer in photosystem II. The vibrational difference spectrum associated with the reduction of photosystem II acceptor quinones is of interest. Previously, a high concentration of the photosystem II donor, hydroxylamine, has been used to obtain a spectrum attributed to QA- -QA (Berthomieu, C., Nabedryk, E., Mantele, W. and Breton, J. FEBS Lett. (1990) 269, 363). Here, we use electron paramagnetic resonance, Fourier transform infrared spectroscopy, and 15N isotopic labeling to show that the difference infrared spectrum, obtained under these conditions, also exhibits a contribution from the oxidation of chlorophyll.

A difference infrared study of hydrogen bonding to the Z. tyrosyl radical of photosystem II.

Photosystem II, the photosynthetic water oxidizing complex, contains two well characterized redox active tyrosines, D and Z. D forms a stable radical of unknown function. Z is an electron carrier between the primary chlorophyll donor and the manganese catalytic site. The vibrational difference spectra associated with the oxidation of tyrosines Z and D have been obtained through the use of infrared spectroscopy (MacDonald, G. M., Bixby, K.A., and Barry, B.A. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 11024-11028). Here, we examine the effect of deuterium exchange on these vibrational difference spectra. While the putative C-O vibration of stable tyrosine radical D. downshifts in 2H2O, the putative C-O vibration of tyrosine radical Z. does not. This result is consistent with the existence of a hydrogen bond to the phenol oxygen of the D. radical; we conclude that a hydrogen bond is not formed to the Z. radical. In an effort to identify the amino acid residue that is the proton acceptor for Z, we have performed global 15N labeling. While significant 15N shifts are observed in the vibrational difference spectrum, substitution of a glutamine for a histidine that is predicted to lie in the environment of tyrosine Z has little or no effect on the difference infrared spectrum. There is also no significant change in the yield or lineshape of the Z. EPR signal under continuous illumination in this mutant. Our results are inconsistent with the possibility that this residue, histidine 190 of the D1 polypeptide, acts as the sole proton acceptor for tyrosine Z.

Comparison of cytochrome b-559 content in photosystem II complexes from spinach and Synechocystis species PCC 6803.

Cytochrome b-559 is an integral component of photosystem II complexes from both plants and cyanobacteria. However, the number of cytochrome b-559 associated with the photosystem II reaction center has been the subject of controversy. Some studies have concluded that there is one heme equivalent of cytochrome b-559 per reaction center, some studies have found two, and some studies have reported intermediate values. Most of the previous experiments have used only one method to quantitate the antenna size of the preparation. In this study, we compare the cytochrome b-559 content in a cyanobacterial and a plant photosystem II preparation. The plant preparation is derived from spinach, and previous work has shown that it has an antenna size of approximately 100 chlorophylls [MacDonald, G. M., & Barry, B. A. (1992) Biochemistry 31, 9848-9856]. The cyanobacterial preparation is from Synechocystis sp. PCC 6803, and previous work has shown that it has an antenna size of approximately 60 chlorophylls [Noren, G. H., Boerner, R. J., & Barry, B. A. (1991) Biochemistry 30, 3943-3950]. Both preparations are isolated through the use of ion-exchange chromatography, and both preparations are monodisperse in the same nonionic detergent. In our comparative study, we quantitate antenna size by three different methods. Our work shows that, depending on the method used to estimate antenna size, the oxygen-evolving spinach photosystem II preparation contains 0.82-1.0 cytochrome b-559 per reaction center, while the oxygen-evolving cyanobacterial preparation contains 1.5-2.1 cytochrome b-559 per reaction center.