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Biomedical subjects

P Gustafsson

Publications and source records attributed to P Gustafsson.

At least 19 recordsLinked to original sources
PubMed1998

[Hyperactivity syndrome is common among prisoners. ADHD not only a pediatric psychiatric diagnosis].

Although ADHD (attention deficit hyperactivity disorder) is one of the most common psychiatric disorders in children, much less is known about its prevalence among adults (where the clinical picture may vary), and it is almost never diagnosed in adult psychiatry. The article consists in a report showing the disorder to have been a common finding in a group of prison inmates, and to have been characterised by strong relationships with a series of other psychiatric disorders (e.g. anxiety and personality disorders) with the presence of self-reported anomalous alcohol reactions, and with the degree of criminality. Current diagnostic practice is unfortunate, partly due to the risk of overdiagnosis of anxiety and personality disorders, and partly due to the risk of missing a condition possibly amenable to treatment.

Adult↗
PubMed1998

The cyanobacterium Synechococcus resists UV-B by exchanging photosystem II reaction-center D1 proteins.

Current ambient UV-B levels can significantly depress productivity in aquatic habitats, largely because UV-B inhibits several steps of photosynthesis, including the photooxidation of water catalyzed by photosystem II. We show that upon UV-B exposure the cyanobacterium Synechococcus sp. PCC 7942 rapidly changes the expression of a family of three psbA genes encoding photosystem II D1 proteins. In wild-type cells the psbAI gene is expressed constitutively, but strong accumulations of psbAII and psbAIII transcripts are induced within 15 min of moderate UV-B exposure (0.4 W/m2). This transcriptional response causes an exchange of two distinct photosystem II D1 proteins. D1:1 is encoded by psbAI, but on UV-B exposure, it is largely replaced by the alternate D1:2 form, encoded by both psbAII and psbAIII. The total content of D1 and other photosystem II reaction center protein, D2, remained unchanged throughout the UV exposure, as did the content and composition of the phycobilisome. Wild-type cells suffered only slight transient inhibition of photosystem II function under UV-B exposure. In marked contrast, under the same UV-B treatment, a mutant strain expressing only psbAI suffered severe (40%) and sustained inhibition of photosystem II function. Another mutant strain with constitutive expression of psbAII and psbAIII was almost completely resistant to the UV-B treatment, showing no inhibition of photosystem II function and only a slight drop in electron transport. In Synechococcus the rapid exchange of alternate D1 forms, therefore, accounts for much of the cellular resistance to UV-B inhibition of photosystem II activity and photosynthetic electron transport. This molecular plasticity may be an important element in community-level responses to UV-B, where susceptibility to UV-B inhibition of photosynthesis changes diurnally.

Bacterial Proteins↗
PubMed1998

Chlorophyll fluorescence analysis of cyanobacterial photosynthesis and acclimation.

Cyanobacteria are ecologically important photosynthetic prokaryotes that also serve as popular model organisms for studies of photosynthesis and gene regulation. Both molecular and ecological studies of cyanobacteria benefit from real-time information on photosynthesis and acclimation. Monitoring in vivo chlorophyll fluorescence can provide noninvasive measures of photosynthetic physiology in a wide range of cyanobacteria and cyanolichens and requires only small samples. Cyanobacterial fluorescence patterns are distinct from those of plants, because of key structural and functional properties of cyanobacteria. These include significant fluorescence emission from the light-harvesting phycobiliproteins; large and rapid changes in fluorescence yield (state transitions) which depend on metabolic and environmental conditions; and flexible, overlapping respiratory and photosynthetic electron transport chains. The fluorescence parameters FV/FM, FV'/FM',qp,qN, NPQ, and phiPS II were originally developed to extract information from the fluorescence signals of higher plants. In this review, we consider how the special properties of cyanobacteria can be accommodated and used to extract biologically useful information from cyanobacterial in vivo chlorophyll fluorescence signals. We describe how the pattern of fluorescence yield versus light intensity can be used to predict the acclimated light level for a cyanobacterial population, giving information valuable for both laboratory and field studies of acclimation processes. The size of the change in fluorescence yield during dark-to-light transitions can provide information on respiration and the iron status of the cyanobacteria. Finally, fluorescence parameters can be used to estimate the electron transport rate at the acclimated growth light intensity.

Acclimatization↗
PubMed1997

Long-term stimulant treatment of children with attention-deficit hyperactivity disorder symptoms. A randomized, double-blind, placebo-controlled trial.

BACKGROUND: We wanted to study the effects of amphetamine on symptoms of attention-deficit hyperactivity disorder (ADHD) over a longer period than has been reported in previous studies of central stimulants in this condition. METHODS: Sixty-two children, aged 6 to 11 years, meeting DSM-III-R symptom criteria for ADHD participated in a parallel-group design, randomized, double-blind, placebo-controlled study of amphetamine treatment. Treatment was not restricted to children with "pure" ADHD, ie, some had comorbid diagnoses. In the amphetamine group, children received active treatment for 15 months. RESULTS: Amphetamine was clearly superior to placebo in reducing inattention, hyperactivity, and other disruptive behavior problems and tended to lead to improved results on the Wechsler Intelligence Scale for Children--Revised. Treatment failure rate was considerably lower and time to treatment failure was longer in the amphetamine group. Adverse effects were few and relatively mild. CONCLUSION: The results of this long-term, placebo-controlled study of the central stimulant amphetamine in the treatment of ADHD indicate that there are remaining positive effects of the drug 15 months after starting treatment.

Abdominal Pain↗
PubMed1997

Development of Arabidopsis thaliana leaves at low temperatures releases the suppression of photosynthesis and photosynthetic gene expression despite the accumulation of soluble carbohydrates.

Arabidopsis thaliana plants were grown at 23 degrees C and changes in carbohydrate metabolism, photosynthesis and photosynthetic gene expression were studied after the plants were shifted to 5 degrees C. The responses of leaves shifted to 5 degrees C after development at 23 degrees C are compared to leaves that developed at 5 degrees C. Shifting warm developed leaves to 5 degrees C lead to a severe suppression of photosynthesis that correlated with a rapid and sustained accumulation of hexose phosphates and soluble sugars. Associated with the suppression of photosynthesis and the accumulation of soluble sugars was a reduction in the amount of transcript for genes encoding photosynthetic proteins (cab and rbcS). In contrast, leaves that developed at 5 degrees C showed an increase in photosynthesis and control levels of photosynthetic gene expression. This recovery occurred even though leaves that developed at 5 degrees C maintained large pools of soluble sugars. Leaves that developed at 5 degrees C also showed a strong upregulation of the cytosolic pathway for soluble sugar synthesis but not of the chloroplastic pathway for starch synthesis. This was shown at the level of both enzyme activity and the amount of transcript. Thus, development of Arabidopsis leaves at 5 degrees C resulted in metabolic changes that enabled them to produce and accumulate large soluble sugar pools without any associated suppression of photosynthesis or photosynthetic gene expression. These changes were also associated with enhanced freezing tolerance. We suggest that this reprogramming of carbohydrate metabolism associated with development at low temperature is essential to the development of full freezing tolerance and for winter survival of over-wintering herbaceous annuals.

Adaptation, Physiological↗
PubMed1996

Over-production of the D1:2 protein makes Synechococcus cells more tolerant to photoinhibition of photosystem II.

Over-expression of the psbAIII gene encoding for the D1 protein (form II; D1:2) of the photosystem II reaction centre in the Synechococcus sp. PCC 7942 was studied using a tac promoter and the lacIQ system. Over-expression was induced with 40 microgram/ml IPTG in the growth medium for either 6 or 12 h at growth irradiance (50 mumol photons m-2 s-1). This treatment doubled the amount of psbAII/III mRNA and the D1:2 protein in membranes but decreased the amount of psbAI messages and the D1:1 protein. The total amount of both heterodimeric reaction centre proteins, D1 and D2, remained constant under growth light conditions, indicating that the number of PSII centres in the membranes was not affected, only the form of the D1 protein was changed from D1:1 to D1:2 in most centres. When the cells were photoinhibited either at 500 or 1000 mumol photons m-2 s-1, in the presence or absence of the protein synthesis inhibitor lincomycin, the D1:2 protein remained at a higher level in cells in which over-expression had been induced by IPTG. These cells were also less prone to photoinhibition of PSII. It is suggested that the tolerance of cells to photoinhibition increases when most PSII reaction centres contain the D1:2 protein at the beginning of high irradiance. This tolerance is further strengthened by maintaining psbAIII gene over-expression during the photoinhibitory treatment.

Amino Acid Sequence↗
PubMed1995

Electron transport regulates exchange of two forms of photosystem II D1 protein in the cyanobacterium Synechococcus.

Synechococcus sp. PCC 7942 modulates photosynthetic function by transiently replacing the constitutive D1 photosystem II protein, D1:1, with an alternate form, D1:2, to help counteract photoinhibition under excess light. We show that a temperature drop from 37 to 25 degrees C also drives D1:1/D1:2 exchange under constant, moderate light. Chilling or light-induced D1 exchange results from rapid loss of psbAI message coding for D1:1 and accumulation of psbAII and psbAIII messages coding for D1:2. During chilling, a large pool of a novel form, D1:2*, transiently accumulates, distinguishable from normal D1 by an increase in apparent molecular mass. D1:2* is not phosphorylated and is probably a functionally inactive, incompletely processed precursor. After acclimation to 25 degrees C, D1:2* disappears and D1:1 again predominates, although substantial D1:2 remains. Partial inhibition of electron transport under constant, moderate light also triggers the D1 exchange process. These treatments all increase excitation pressure on photosystem II relative to electron transport. Therefore, information from photosynthetic electron transport regulates D1 exchange without any requirement for a change in light intensity or quality, possibly via a redox sensing mechanism proximal to photosystem II.

Antioxidants↗
PubMed1995

Chlorophyll a/b-binding proteins, pigment conversions, and early light-induced proteins in a chlorophyll b-less barley mutant.

Monospecific polyclonal antibodies have been raised against synthetic peptides derived from the primary sequences from different plant light-harvesting Chl a/b-binding (LHC) proteins. Together with other monospecific antibodies, these were used to quantify the levels of the 10 different LHC proteins in wild-type and chlorina f2 barley (Hordeum vulgare L.), grown under normal and intermittent light (ImL). Chlorina f2, grown under normal light, lacked Lhcb1 (type I LHC II) and Lhcb6 (CP24) and had reduced amounts of Lhcb2, Lhcb3 (types II and III LHC II), and Lhcb4 (CP 29). Chlorina f2 grown under ImL lacked all LHC proteins, whereas wild-type ImL plants contained Lhcb5 (CP 26) and a small amount of Lhcb2. The chlorina f2 ImL thylakoids were organized in large parallel arrays, but wild-type ImL thylakoids had appressed regions, indicating a possible role for Lhcb5 in grana stacking. Chlorina f2 grown under ImL contained considerable amounts of violaxanthin (2-3/reaction center), representing a pool of phototransformable xanthophyll cycle pigments not associated with LHC proteins. Chlorina f2 and the plants grown under ImL also contained early light-induced proteins (ELIPs) as monitored by western blotting. The levels of both ELIPs and xanthophyll cycle pigments increased during a 1 h of high light treatment, without accumulation of LHC proteins. These data are consistent with the hypothesis that ELIPs are pigment-binding proteins, and we suggest that ELIPs bind photoconvertible xanthophylls and replace "normal" LHC proteins under conditions of light stress.

Amino Acid Sequence↗
PubMed1994

Over-production of the D1 protein of photosystem II reaction centre in the cyanobacterium Synechococcus sp. PCC 7942.

The unicellular cyanobacterium Synechococcus sp. PCC 7942 has three psbA genes encoding two different forms of the photosystem II reaction centre protein D1 (D1:1 and D1:2). The level of expression of these psbA genes and the synthesis of D1:1 and D1:2 are strongly regulated under varying light conditions. In order to better understand the regulatory mechanisms underlying these processes, we have constructed a strain of Synechococcus sp. PCC 7942 capable of over-producing psbA mRNA and D1 protein. In this study, we describe the over-expression of D1:1 using a tac-hybrid promoter in front of the psbAI gene in combination with lacIQ repressor system. Over-production of D1:1 was induced by growing cells for 12 h at 50 mumol photons m-2 s-1 in the presence of 40 or 80 micrograms/ml IPTG. The amount of psbAI mRNA and that of D1:1 protein in cells grown with IPTG was three times and two times higher, respectively. A higher concentration of IPTG (i.e., 150 micrograms/ml) did not further increase the production of the psbAI message or D1:1. The over-production of D1:1 caused a decrease in the level of D1:2 synthesised, resulting in most PSII reaction centres containing D1:1. However, the over-production of D1:1 had no effect on the pigment composition (chlorophyll a or phycocyanin/number of cells) or the light-saturated rate of photosynthesis. This and the fact that the total amounts of D1 and D2 proteins were not affected by IPTG suggest that the number of PSII centres within the membranes remained unchanged. From these results, we conclude that expression of psbAI can be regulated by using the tac promoter and lacIQ system. However, the accumulation of D1:1 protein into the membrane is regulated by the number of PSII centres.

Amino Acid Sequence↗
PubMed1994

Identification and expression of the chloroplast clpP gene in the conifer Pinus contorta.

The clpP gene from the conifer Pinus contorta was identified and isolated from a chloroplast genomic library by heterologous hybridisation to the second exon of the chloroplast clpP gene in tobacco. DNA sequencing of two overlapping clones revealed an uninterrupted 615 bp open-reading frame with 41 to 65% similarity to the clpP genes in five other chloroplast genomes and Escherichia coli. The 615 bp sequence in P. contorta contained perfectly matched motifs for the serine and histidine active sites of the ClpP protease in E. coli. The location of the clpP gene was determined using a physical map of the P. contorta chloroplast genome, and was found to lie within a 10 kb region between the psbE/F and rpoB genes. Sequencing of the regions adjacent to the clpP gene revealed the first exon of the rps12 gene located 135 bp downstream. The genomic position of the first exon of the rps12 gene in relation to the clpP gene is conserved for all other chloroplast clpP genes identified so far. Northern blot analysis showed that the clpP gene in both P. contorta and P. sylvestris was present in several transcript of different length, ranging from 0.8 to 2.4 kb. The two longer transcripts in P. contorta also included the first exon of the rps12 gene. Mapping of the 5' end of the clpP transcripts by primer extension, however, revealed a single transcription initiation site 53 bp upstream of the first ATG codon. Analysis of total RNA isolated from the two pine species grown in darkness or moderate light conditions (250 mumol photons m-2 s-1) showed no significance difference in the level of expression of the clpP gene. The results suggest that the clpP gene in conifers is part of an operon which includes the first exon of the rps12 and the entire rpl20 gene, and is expressed in a light-independent manner as a polycistronic precursor which later undergoes post-transcriptional processing to give the mature monocistronic clpP mRNA.

ATP-Dependent Proteases↗
PubMed1994

Cloning of the cpcE and cpcF genes from Synechococcus sp. PCC 6301 and their inactivation in Synechococcus sp. PCC 7942.

Two open reading frames denoted as cpcE and cpcF were cloned and sequenced from Synechococcus sp. PCC 6301. The cpcE and cpcF genes are located downstream of the cpcB2A2 gene cluster in the phycobilisome rod operon and can be transcribed independently of the upstream cpcB2A2 gene cluster. The cpcE and cpcF genes were separately inactivated by insertion of a kanamycin resistance cassette in Synechococcus sp. PCC 7942 to generate mutants R2EKM and R2FKM, respectively, both of which display a substantial reduction in spectroscopically detectable phycocyanin. The levels of beta- and alpha-phycocyanin polypeptides were reduced in the R2EKM and R2FKM mutants although the phycocyanin and linker genes are transcribed at normal levels in the mutants as in the wild type indicating the requirement of the functional cpcE and cpcF genes for normal accumulation of phycocyanin. Two biliprotein fractions were isolated on sucrose density gradient from the R2EKM/R2FKM mutants. The faster sedimenting fraction consisted of intact phycobilisomes. The slower sedimenting biliprotein fraction was found to lack phycocyanin polypeptides, thus no free phycocyanin was detected in the mutants. Characterization of the phycocyanin from the mutants revealed that it was chromophorylated, had a lambda max similar to that from the wild type and could be assembled into the phycobilisome rods. Thus, although phycocyanin levels are reduced in the R2EKM and R2FKM mutants, the remaining phycocyanin seems to be chromophorylated and similar to that in the wild type with respect to phycobilisome rod assembly and energy transfer to the core.

Amino Acid Sequence↗
PubMed1993

Two functionally distinct forms of the photosystem II reaction-center protein D1 in the cyanobacterium Synechococcus sp. PCC 7942.

The cyanobacterium Synechococcus sp. PCC 7942 possesses a small psbA multigene family that codes for two distinct forms of the photosystem II reaction-center protein D1 (D1:1 and D1:2). We showed previously that the normally predominant D1 form (D1:1) was rapidly replaced with the alternative D1:2 when cells adapted to a photon irradiance of 50 mumol.m-2.s-1 are shifted to 500 mumol.m-2.s-1 and that this interchange was readily reversible once cells were allowed to recover under the original growth conditions. By using the psbA inactivation mutants R2S2C3 and R2K1 (which synthesize only D1:1 and D1:2, respectively), we showed that this interchange between D1 forms was essential for limiting the degree of photoinhibition as well as enabling a rapid recovery of photosynthesis. In this report, we have extended these findings by examining whether any intrinsic functional differences exist between the two D1 forms that may afford increased resistance to photoinhibition. Initial studies on the rate of D1 degradation at three photon irradiances (50, 200, and 500 mumol.m-2.s-1) showed that the rates of degradation for both D1 forms increase with increasing photon flux density but that there was no significant difference between D1:1 and D1:2. Analysis of light-response curves for oxygen evolution for the mutants R2S2C3 and R2K1 revealed that cells with photosystem II reaction centers containing D1:2 have a higher apparent quantum yield (approximately 25%) than cells possessing D1:1. Further studies using chlorophyll a fluorescence measurements confirmed that R2K1 has a higher photochemical yield than R2S2C3; that is, a more efficient conversion of excitation energy from photon absorption into photochemistry. We believe that the higher photochemical efficiency of reaction centers containing D1:2 is causally related to the preferential induction of D1:2 at high light and thus may be an integral component of the protection mechanism within Synechococcus sp. PCC 7942 against photoinhibition.

Bacterial Proteins↗
PubMed1993

Rapid interchange between two distinct forms of cyanobacterial photosystem II reaction-center protein D1 in response to photoinhibition.

We have studied photoinhibition of photosynthesis in the cyanobacterium Synechococcus sp. PCC 7942, which possesses two distinct forms of the photosystem II reaction-center protein D1 (D1:1 and D1:2). We report here that when cells adapted to a growth irradiance of 50 mumol.m-2.s-1 are exposed to an irradiance of 500 mumol.m-2.s-1, the normally predominant D1 form (D1:1) is rapidly replaced with the alternative D1:2. This interchange is not only complete within the first hour of photoinhibition but is also fully reversible once cells are returned to 50 mumol.m-2 x s-1. By using a mutant that synthesizes only D1:1, we show that the failure to replace D1:1 with D1:2 during photoinhibition results in severe loss of photosynthetic activity as well as a diminished capacity to recover after the stress period. We believe that this interchange between D1 forms may constitute an active component in a protection mechanism unique among photosynthetic organisms that enables cyanobacteria to effectively cope with and recover from photoinhibition.

Cyanobacteria↗
PubMed1993

Regulation of phycobilisome rod proteins and mRNA at different light intensities in the cyanobacterium Synechococcus 6301.

The regulation of the light-harvesting antennae, the phycobilisome (Pbs), and the cpcB1A1-cpcH-cpcI-cpcD operon encoding the structural proteins of the Pbs rod, was studied in the cyanobacterium, Synechococcus sp. PCC 6301, when grown at different light intensities (li). Pbs were purified and their linker protein (LP) profiles analyzed on SDS-polyacrylamide gels. At increasing li, the amount of the distal 30-kDa LP decreased prior to any change in the amount of the proximal 33-kDa LP, indicating a sequential increase in the Pbs rod length. While the amount of LP in the rod decreased with increasing li, the levels of the LP mRNAs increased. Post-transcriptional regulation of the expression of the polycistronic cpcB1A1-cpcH-cpcI-cpcD mRNA was inferred from these observations. The half-life of the mRNAs studied was typically found to be 7 min with four exceptions: (1 and 2) the half-lives for the 3.4- and 3.7-kb polycistronic LP mRNAs were 16 and 1 min at the low (lli) and high li (hli), respectively; (3) the half-life of the 1.4-kb cpcB1A1 mRNA was 2 min at lli; and (4) the 1.3-kb cpcB1A1 transcript had a half-life of 10 min at lli. At hli, it was found that the 1.3-kb cpcB1A1 transcript did not start to disappear until the amount of the 1.4-kb cpcB1A1 transcript had reached the level equal to that of the 1.3-kb mRNA, implying that the 1.4-kb transcript might be processed to the 1.3-kb form.

Amino Acid Sequence↗