Search PubMed⌕ Search

Biomedical subjects

S Berry

Publications and source records attributed to S Berry.

At least 19 recordsLinked to original sources
PubMed2001

A giant chlorophyll-protein complex induced by iron deficiency in cyanobacteria.

Cyanobacteria are abundant throughout most of the world's water bodies and contribute significantly to global primary productivity through oxygenic photosynthesis. This reaction is catalysed by two membrane-bound protein complexes, photosystem I (PSI) and photosystem II (PSII), which both contain chlorophyll-binding subunits functioning as an internal antenna. In addition, phycobilisomes act as peripheral antenna systems, but no additional light-harvesting systems have been found under normal growth conditions. Iron deficiency, which is often the limiting factor for cyanobacterial growth in aquatic ecosystems, leads to the induction of additional proteins such as IsiA (ref. 3). Although IsiA has been implicated in chlorophyll storage, energy absorption and protection against excessive light, its precise molecular function and association to other proteins is unknown. Here we report the purification of a specific PSI-IsiA supercomplex, which is abundant under conditions of iron limitation. Electron microscopy shows that this supercomplex consists of trimeric PSI surrounded by a closed ring of 18 IsiA proteins binding around 180 chlorophyll molecules. We provide a structural characterization of an additional chlorophyll-containing, membrane-integral antenna in a cyanobacterial photosystem.

Bacterial Proteins↗
PubMed2001

Fluorescent probes for non-invasive bioenergetic studies of whole cyanobacterial cells.

Fluorescent DeltapH and DeltaPsi indicators have been screened for the non-invasive monitoring of bioenergetic processes in whole cells of the cyanobacterium Synechocystis sp. PCC 6803. Acridine yellow and Acridine orange proved to be the best DeltapH indicators for the investigation of thylakoid and cytoplasmic membrane energization: While Acridine yellow indicated only cytosolic energization, Acridine orange showed signals from both the thylakoid lumen and the cytosol that could be separated kinetically. Both indicators were applied successfully to monitor cellular energetics, such as the interplay of linear and cyclic photosynthetic electron transport, osmotic adaptation and solute transport across the cytoplasmic membrane. In contrast, useful membrane potential indicators were more difficult to find, with Di-4-ANEPPS and Brilliant cresyl blue being the only promising candidates for further studies. Finally, Acridine yellow and Acridine orange could also be applied successfully for the thermophilic cyanobacterium Synechococcus elongatus. Different from Synechocystis sp. PCC 6803, where both respiration and ATP hydrolysis could be utilized for cytoplasmic membrane energization, proton extrusion at the cytoplasmic membrane in Synechococcus elongatus was preferentially driven by ATP hydrolysis.

Acridine Orange↗
PubMed2001

A regulatory role of the PetM subunit in a cyanobacterial cytochrome b6f complex.

To investigate the function of the PetM subunit of the cytochrome b6f complex, the petM gene encoding this subunit was inactivated by insertional mutagenesis in the cyanobacterium Synechocystis PCC 6803. Complete segregation of the mutant reveals a nonessential function of PetM for the structure and function of the cytochrome b6f complex in this organism. Photosystem I, photosystem II, and the cytochrome b6f complex still function normally in the petM- mutant as judged by cytochrome f re-reduction and oxygen evolution rates. In contrast to the wild type, however, the content of phycobilisomes and photosystem I as determined from 77 K fluorescence spectra is reduced in the petM- strain. Furthermore, whereas under anaerobic conditions the kinetics of cytochrome f re-reduction are identical, under aerobic conditions these kinetics are slower in the petM- strain. Fluorescence induction measurements indicate that this is due to an increased plastoquinol oxidase activity in the mutant, causing the plastoquinone pool to be in a more oxidized state under aerobic dark conditions. The finding that the activity of the cytochrome b6f complex itself is unchanged, whereas the stoichiometry of other protein complexes has altered, suggests an involvement of the PetM subunit in regulatory processes mediated by the cytochrome b6f complex.

Cloning, Molecular↗
PubMed2001

Development of the 25-item National Eye Institute Visual Function Questionnaire.

OBJECTIVE: To develop and test the psychometric properties of a 25-item version of the National Eye Institute Visual Function Questionnaire (NEI VFQ-25). DESIGN: Prospective observational cohort study of persons with 1 of 5 chronic eye diseases or low vision who were scheduled for nonurgent visits in ophthalmology practices and a reference sample of persons without eye disease. SETTING: Eleven university-based ophthalmology practices and the NEI Clinical Center. PATIENTS: Eligible participants had to have 1 of the following eye conditions: age-related cataracts, age-related macular degeneration, diabetic retinopathy, primary open-angle glaucoma, cytomegalovirus retinitis, or low vision from any cause. Seven of the 12 sites also enrolled persons in a reference sample. Reference sample participants had no evidence of underlying eye disease but were scheduled for either screening eye examinations or correction of refractive error. All eligible persons had to be 21 years or older, English speaking, and cognitively able to give informed consent and participate in a health status interview. MEASUREMENTS AND MAIN RESULTS: To provide the data needed to create the NEI VFQ-25, all subjects completed an interview that included the 51-item NEI VFQ. Estimates of internal consistency indicate that the subscales of the NEI VFQ-25 are reliable. The validity of the NEI VFQ-25 is supported by high correlations between the short- and long-form versions of the measure, observed between-group differences in scores for persons with different eye diseases of varying severity, and the moderate-to-high correlations between the NEI VFQ-25 subscales that have the most to do with central vision and measured visual acuity. CONCLUSIONS: The reliability and validity of the NEI VFQ-25 are comparable to those of the 51-item NEI VFQ field test version of the survey. This shorter version will be more feasible in settings such as clinical trials where interview length is a critical consideration. In addition, preliminary analyses indicate that the psychometric properties of the NEI VFQ-25 are robust for the eye conditions studied; this suggests that the measure will provide reproducible and valid data when used across multiple conditions of varying severity.

Chronic Disease↗
PubMed2001

Molecular evidence for diverse populations of cassava-infecting begomoviruses in southern Africa.

In this paper we describe results obtained from screening field populations of begomoviruses from infected cassava from six countries in southern Africa. It was found that African cassava mosaic virus occurs in five of the six countries (except Angola), East African cassava mosaic virus is present in five countries (except Zambia) and South African cassava mosaic virus was detected only in South Africa and Swaziland. In addition, we report for the first time in southern Africa, the appearance of the Ugandan variant virus (UgV) which was found frequently in mixed infections with other cassava-infecting begomoviruses.

Capsid↗
PubMed2001

Differentiation of cassava-infecting begomoviruses using heteroduplex mobility assays.

Cassava mosaic disease is an enormous problem affecting the viability and productivity of cassava in all the developing regions in Africa. The disease is now known to be caused by a number of cassava-infecting begomoviruses. New viruses and viral strains continue to be discovered and due to the lack of cloning and sequencing facilities in many African laboratories, a simple, rapid and sensitive technique is needed for screening of cassava plantations. Here we report on the development of a heteroduplex mobility assay (HMA) which could be used for the testing of viral-infected cassava. The assay involves amplifying the highly conserved core region of the coat protein gene of field isolates followed by denaturing and annealing with a number of reference strains. The HMA profiles in this study were able to differentiate four different viral species and 11 different virus strains, and showed a good correlation with sequencing results and phylogenetic comparisons with other sequenced cassava viruses. This technique is sensitive and rapid and has the added advantage of being able to detect mixtures of viruses in field-grown cassava.

Capsid↗
PubMed2001

Kinetic modeling of the photosynthetic electron transport chain.

A simulation model of the photosynthetic electron transport chain operating under steady state conditions is presented. The model enables the calculation of (1) the rates of electron transport and transmembrane proton translocation, (2) the proton/electron stoichiometry, (3) the number of electrons stored in the different redox centers and (4) the stationary transmembrane pH difference. Light intensity and proton permeability of the thylakoid membrane are varied in order to compare the predictions of the model with experimental data. The routes of electron transport and proton translocation are simulated by two coupled arithmetic loops. The first one represents the sequence of reaction steps making up the linear electron transport chain and the Q-cycle. This loop yields the electron flow rate and the proton/electron ratio. The second loop balances the H+ fluxes and yields the internal H+ concentration. The bifurcation of the electron transport pathways at the stage of plastoquinol oxidation is obligatory. The first electron enters always the linear branch and is transferred to photosystem I. The electron of the remaining semiquinone can enter the Q-cycle or, alternatively, the semiquinone can be lost from the cytochrome b6f complex. The competition between these two reactions explains the experimentally observed variability of the proton/electron ratio. We also investigated additional model variants, where the variation of the proton/electron stoichiometry is attributed to other loss reactions within the cytochrome b6f complex. However, the semiquinone detachment seems to be the best candidate for a satisfactory description of the experimental data. Additional calculations were done in order to assess the effects of the movement of the Rieske protein on linear electron transport; it was found that this conformational change does not limit the electron transport rate, if it occurs with a time constant of at least 1000 s(-1).

Computer Simulation↗
PubMed2001

Perceptions of important retention and recruitment factors by therapists in northwestern Ontario.

Recruitment and retention of health professionals in rural and remote communities are well-known challenges. Although the literature states that lifestyle factors and being from a rural background influence recruitment and retention, much of the research is dated and of limited relevance to rehabilitation professionals. This study reports on a survey of physical therapists (PTs) and occupational therapists (OTs) in northwestern Ontario. Seventy-four percent of the OTs and PTs from this geographically isolated region of Canada responded to a mail survey examining factors that influenced their job recruitment and retention decisions. Availability of leisure and recreation activities, proximity of family of origin, need for OTs and PTs and influence of spouse or partner frequently contributed to recruitment decisions and were also important in retention decisions. Although professional autonomy was an important source of job satisfaction for the respondents, almost one-third reported a feeling of professional isolation. Professional development initiatives appeared to influence job satisfaction but were unlikely to influence working life decisions. The findings suggest that recruitment and retention strategies should be multifaceted to reflect the complexity of therapists' decision-making.

Adult↗
PubMed2001

Candidate disease resistance genes in sunflower cloned using conserved nucleotide-binding site motifs: genetic mapping and linkage to the downy mildew resistance gene Pl1.

Disease resistance gene candidates (RGCs) belonging to the nucleotide-binding site (NBS) superfamily have been cloned from numerous crop plants using highly conserved DNA sequence motifs. The aims of this research were to (i) isolate genomic DNA clones for RGCs in cultivated sunflower (Helianthus annuus L.) and (ii) map RGC markers and Pl1, a gene for resistance to downy mildew (Plasmopara halstedii (Farl.) Berl. & de Toni) race 1. Degenerate oligonucleotide primers targeted to conserved NBS DNA sequence motifs were used to amplify RGC fragments from sunflower genomic DNA. PCR products were cloned, sequenced, and assigned to 11 groups. RFLP analyses mapped six RGC loci to three linkage groups. One of the RGCs (Ha-4W2) was linked to Pl1, a downy mildew resistance gene. A cleaved amplified polymorphic sequence (CAPS) marker was developed for Ha-4W2 using gene-specific oligonucleotide primers. Downy mildew susceptible lines (HA89 and HA372) lacked a 276-bp Tsp5091 restriction fragment that was present in downy mildew resistant lines (HA370, 335, 336, 337, 338, and 339). HA370 x HA372 F2 progeny were genotyped for the Ha-4W2 CAPS marker and phenotyped for resistance to downy mildew race 1. The CAPS marker was linked to but did not completely cosegregate with Pl1 on linkage group 8. Ha-4W2 was found to comprise a gene family with at least five members. Although genetic markers for Ha-4W2 have utility for marker-assisted selection, the RGC detected by the CAPS marker has been ruled out as a candidate gene for Pl1. Three of the RGC probes were monomorphic between HA370 and HA372 and still need to be mapped and screened for linkage to disease resistance loci.

Base Sequence↗
PubMed2001

An integrated restriction fragment length polymorphism--amplified fragment length polymorphism linkage map for cultivated sunflower.

Restriction fragment length polymorphism (RFLP) maps have been constructed for cultivated sunflower (Helianthus annuus L.) using three independent sets of RFLP probes. The aim of this research was to integrate RFLP markers from two sets with RFLP markers for resistance gene candidate (RGC) and amplified fragment length polymorphism (AFLP) markers. Genomic DNA samples of HA370 and HA372, the parents of the F2 population used to build the map, were screened for AFLPs using 42 primer combinations and RFLPs using 136 cDNA probes (RFLP analyses were performed on DNA digested with EcoRI, HindIII, EcoRV, or DraI). The AFLP primers produced 446 polymorphic and 1101 monomorphic bands between HA370 and HA372. The integrated map was built by genotyping 296 AFLP and 104 RFLP markers on 180 HA370 x HA372 F2 progeny (the AFLP marker assays were performed using 18 primer combinations). The HA370 x HA372 map comprised 17 linkage groups, presumably corresponding to the 17 haploid chromosomes of sunflower, had a mean density of 3.3 cM, and was 1326 cM long. Six RGC RFLP loci were polymorphic and mapped to three linkage groups (LG8, LG13, and LG15). AFLP markers were densely clustered on several linkage groups, and presumably reside in centromeric regions where recombination is reduced and the ratio of genetic to physical distance is low. Strategies for targeting markers to euchromatic DNA need to be tested in sunflower. The HA370 x HA372 map integrated 14 of 17 linkage groups from two independent RFLP maps. Three linkage groups were devoid of RFLP markers from one of the two maps.

Chromosome Mapping↗
PubMed2000

Noninvasive diagnosis by Doppler ultrasonography of fetal anemia due to maternal red-cell alloimmunization. Collaborative Group for Doppler Assessment of the Blood Velocity in Anemic Fetuses.

BACKGROUND: Invasive techniques such as amniocentesis and cordocentesis are used for diagnosis and treatment in fetuses at risk for anemia due to maternal red-cell alloimmunization. The purpose of our study was to determine the value of noninvasive measurements of the velocity of blood flow in the fetal middle cerebral artery for the diagnosis of fetal anemia. METHODS: We measured the hemoglobin concentration in blood obtained by cordocentesis and also the peak velocity of systolic blood flow in the middle cerebral artery in 111 fetuses at risk for anemia due to maternal red-cell alloimmunization. Peak systolic velocity was measured by Doppler velocimetry. To identify the fetuses with anemia, the hemoglobin values of those at risk were compared with the values in 265 normal fetuses. RESULTS: Fetal hemoglobin concentrations increased with increasing gestational age in the 265 normal fetuses. Among the 111 fetuses at risk for anemia, 41 fetuses did not have anemia; 35 had mild anemia; 4 had moderate anemia; and 31, including 12 with hydrops, had severe anemia. The sensitivity of an increased peak velocity of systolic blood flow in the middle cerebral artery for the prediction of moderate or severe anemia was 100 percent either in the presence or in the absence of hydrops (95 percent confidence interval, 86 to 100 percent for the 23 fetuses without hydrops), with a false positive rate of 12 percent. CONCLUSIONS: In fetuses without hydrops that are at risk because of maternal red-cell alloimmunization, moderate and severe anemia can be detected noninvasively by Doppler ultrasonography on the basis of an increase in the peak velocity of systolic blood flow in the middle cerebral artery.

Blood Flow Velocity↗
PubMed2000

Myeloid leukaemic cells can lyse fibrin directly.

Purified preparations of circulating leukaemic blast cells from patients with acute myeloid (M1-7) or acute lymphoblastic leukaemia, and the myeloid or lymphoid cells from patients with chronic myeloid or lymphocytic forms of leukaemia, were incorporated into clots prepared from fibrinogen and plasminogen. Patterns of lysis were followed and measured by light transmission in a microtitre plate reader. Mature polymorphonuclear and mononuclear cell fractions from normal individuals were studied concurrently for comparison. Blast cells from the myeloid forms of acute leukaemia (M2-4) and 'myeloid' cell fractions from patients with chronic myeloid leukaemia were capable of lysing plasminogen-containing clots; this activity was neutralized by addition of immunoglobulin against urokinase plasminogen activator (u-PA), but not by anti-tissue plasmogen activator (t-PA). Mature polymorphonuclear and mononuclear cells from normal individuals lacked lytic activity, as did the leukaemic cells from patients with acute lymphoblastic or chronic lymphocytic leukaemia. Lysed blast cells showed the presence of free plasminogen activator on sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) with overlay zymography, also neutralized by anti-u-PA, whereas normal polymorphonuclear and mononuclear cells did not. These observations suggest that mechanisms underlying some forms of severe bleeding in acute myeloid leukaemias have a critical fibrinolytic component generated by the blast cells themselves.

Acute Disease↗
PubMed2000

Access of vulnerable groups to antiretroviral therapy among persons in care for HIV disease in the United States. HCSUS Consortium. HIV Cost and Services Utilization Study.

OBJECTIVE: To employ the behavioral model of health services use in examining the extent to which predisposing, enabling, and need factors explain the treatment of the HIV-positive population in the United States with highly active antiretroviral therapy (HAART). DATA SOURCE: A national probability sample of 2,776 adults under treatment for human immunodeficiency virus (HIV) infection. STUDY DESIGN: The article uses data from the baseline and six-month follow-up surveys. The key independent variables describe vulnerable population groups including women, drug users, ethnic minorities, and the less educated. The dependent variable is whether or not a respondent received HAART by December 1996. DATA COLLECTION: All interviews were conducted using computer-assisted personal interview instruments designed for this study. Ninety-two percent of the baseline interviews were conducted in person and the remainder over the telephone. PRINCIPAL FINDINGS: A multistage logit regression shows that the predisposing factors that have previously described vulnerable groups in the general population with limited access to medical care also define HIV-positive groups who are less likely to gain early access to HAART including women, injection drug users, African Americans, and the least educated (odds ratios, controlling for need, ranged from 0.35 to 0.59). CONCLUSIONS: Those HIV-positive persons with the greatest need (defined by a low CD4 count) are most likely to have early access to HAART, which suggests equitable access. However, some predisposing and enabling variables continue to be important as well, suggesting inequitable access, especially for African Americans and lower-income groups. Policymakers and clinicians need to be sensitized to the continued problems of African Americans and other vulnerable populations in gaining access to such potentially beneficial therapies. Higher income, anonymous test sites, and same-day appointments are important enabling resources.

Adult↗
PubMed1999

Hemangiopericytoma in a child: a case report.

Hemangiopericytoma (HPC) is a rare vascular tumour seen infrequently in the paediatric age group. It has an incidence of about 10% in children. The difficulty in assessing the malignant potential of this tumour may cause confusion to the clinician in deciding the proper line of management.

Adolescent↗
PubMed1999

Proton to electron stoichiometry in electron transport of spinach thylakoids

According to the concept of the Q-cycle, the H+/e- ratio of the electron transport chain of thylakoids can be raised from 2 to 3 by means of the rereduction of plastoquinone across the cytochrome b6f complex. In order to investigate the H+/e- ratio we compared stationary rates of electron transport and proton translocation in spinach thylakoids both in the presence of the artificial electron acceptor ferricyanide and in the presence of the natural acceptor system ferredoxin+NADP. The results may be summarised as follows: (1) a variability of the H+/e- ratio occurs with either acceptor. H+/e- ratios of 3 (or even higher in the case of the natural acceptor system, see below) are decreased towards 2 if strong light intensity and low membrane permeability are employed. Mechanistically this could be explained by proton channels connecting the plastoquinol binding site alternatively to the lumenal or stromal side of the cytochrome b6f complex, giving rise to a proton slip reaction at high transmembrane DeltapH. In this slip reaction protons are deposited on the stromal instead of the lumenal side. In addition to the pH effect there seems to be a contribution of the redox state of the plastoquinone pool to the control of proton translocation; switching over to stromal proton deposition is favoured when the reduced state of plastoquinone becomes dominant. (2) In the presence of NADP a competition of both NADP and oxygen for the electrons supplied by photosystem I takes place, inducing a general increase of the H+/e- ratios above the values obtained with ferricyanide. The implications with respect to the adjustment of a proper ATP/NADPH ratio for CO2 reduction are discussed.

Journal Article↗
PubMed1999

Estrous cyclicity and behavioral sensitization in female rats following repeated intravenous cocaine administration.

Repeated intermittent administration of cocaine is well known to produce behavioral sensitization in male animals. The present studies explored whether intact adult female rats maintained normal estrous patterns in response to repeated IV cocaine administration and whether behavioral sensitization occurred with this route of administration. Adult female Sprague-Dawley rats (N = 48) were surgically implanted with an intravenous access port. Animals received 3.0 mg/kg IV cocaine once/day for 14 days. Daily vaginal lavages indicated that female rats continued to cycle normally throughout the experiment. Estimates of statistical power for detecting alterations in estrous cycle length ranged from 0.61-0.95 for small (0.1) to large (0.4) effect sizes. Moreover, no cocaine-treated animals displayed persistent vaginal estrus or were acyclic and cocaine treatment did not decrease body weight. Immediately after the cocaine injection, animals were placed in IR photocell activity chambers for 60 min. Female rats displayed a significant 75% increase in locomotor activity across the 14-day time course of IV cocaine injections. These data indicate that 3.0 mg/kg of IV cocaine does not interfere with normal estrous cyclicity, and that behavioral sensitization occurs in female rats following repeated daily IV cocaine dosing. Collectively, these data suggest that the IV cocaine-dosing model may be particularly useful in exploring the gender-dependent effects of cocaine using intact female rats.

Animals↗