Structural characterization of high 800 nm-absorbing light-harvesting complexes from Rhodospirillales from their resonance Raman spectra

Resonance Raman spectroscopy provided evidence that high 800 nm-absorbing antennae from Rhodopseudomonas (Rps.) acidophila and Rps. palustris have similar structures around their dweller bacteriochlorophylls. These host-site structures are different from those of B 850-800 complexes from Chromatiaceae, which also exhibit a high absorbance at 800 nm. As also shown by previous biochemical data, these complexes might be stoichiometrically different from other antenna complexes, having one more BChl per minimal size unit of protein. A new classification of B 850-800 complexes is proposed, on the basis of resonance Raman and biochemical data: this classification distinguishes a class of B 850-800 S (involving the B 850-800 complexes from sulfur purple bacteria), two classes of B 850-800 NS (involving the B 850-800 complexes from non sulfur purple bacteria) and a class of H 800 complexes (involving the B 850-800 complexes from non sulfur purple bacteria exhibiting a high absorbance at 800 nm).     

Assembly of LH2 light-harvesting complexes in Rhodopseudomonas palustris cells illuminated by blue and red light

We investigated the formation of the B800-850 complex in cells of the bacterium Rhodopseudomonas palustris AB illuminated by red and blue light under anaerobic growth conditions. Under red illumination, the B800-850 complex was assembled with a reduced absorption band at 850 nm. The results of re-electrophoresis of the B800-850 complex and oxidation in the presence of potassium iridate suggest its heterogeneity. It may be a mixture of two complexes (B800 and B800-850). The B800-850 complex lacks the capacity for conformational transitions if assembled under blue illumination. Accordingly, the light-harvesting complex assembled in the blue light contains polypeptides that are not synthesized under normal conditions or at increased or decreased light intensities. The mechanism of regulation of the synthesis of the polypeptides of light-harvesting B800-850 complex and its dependence on the spectral composition of the light is discussed.     

Assembly of LH2 light-harvesting complexes in Rhodopseudomonas palustris cells illuminated by blue and red light

We investigated the formation of the B800-850 complex in cells of the bacterium Rhodopseudomonas palustris AB illuminated by red and blue light under anaerobic growth conditions. Under red illumination, the B800-850 complex was assembled with a reduced absorption band at 850 nm. The results of re-electrophoresis of the B800-850 complex and oxidation in the presence of potassium iridate suggest its heterogeneity. It may be a mixture of two complexes (B800 and B800-850). The B800-850 complex lacks the capacity for conformational transitions if assembled under blue illumination. Accordingly, the light-harvesting complex assembled in the blue light contains polypeptides that are not synthesized under normal conditions or at increased or decreased light intensities. The mechanism of regulation of the synthesis of the polypeptides of light-harvesting the B800-850 complex and its dependence on the spectral composition of the light is discussed.     

Crystallization of the B800-820 light-harvesting complex from Rhodopseudomonas acidophila strain 7750.

The B800-820 light-harvesting complex, an integral membrane protein, from Rhodopseudomonas acidophila strain 7750 has been crystallized. The tabular plates have a hexagonal unit cell of a = b = 121.8 A and c = 283.1 A and belong to the space group R32. X-ray diffraction data have been collected to 6 A resolution, using an area detector on a rotating anode source. The B800-820 light-harvesting complex is comprised of four low molecular weight apoproteins (B800-820 alpha 1, B800-820 alpha 2, B800-820 beta 1 and B800-820 beta 2). Polyacrylamide gel electrophoresis shows that the complex exists as an oligomeric assembly, with an apparent molecular weight of 92,000.     

Prevalence of Toxoplasma gondii antibodies in muskox (Ovibos moschatus) sera from northern Canada

Prevalence of antibodies to Toxoplasma gondii was determined in 203 muskoxen (Ovibos moschatus) from 3 geographically distinct areas of northern Canada (near the hamlets of Kugluktuk and Cambridge Bay, Nunavut and Holman, Northwest Territories) by the modified agglutination test (MAT). Antibodies were found in 13 (6.4%) of 203 animals with MAT titers of 1:25 in 2, 1:50 in 7, 1:200 in 2, 1:400 in 1, and 1:800 in 1. The 4 muskoxen with MAT titers > or =1:200 were adult females and were among 10 animals examined from a mainland population near Kugluktuk. The seroprevalence was lower in Victoria Island muskoxen collected near Cambridge Bay (4.6% of 151) and Holman (4.8% of 42). This is the first serologic survey for T. gondii infection in muskoxen.     

Effect of high levels of dietary vitamin C on the blood responses of matrinxã (Brycon amazonicus)

Juvenile matrinx? (Brycon amazonicus) were fed with different dietary vitamin C (ascorbic acid or AA) concentrations for 2 months in order to evaluate its effect on the physiological condition of this species. Five treatments were tested: Reference diet-RD (350 mg AA kg(-1) and 45% crude protein commercial feed); C400, C500, C600 and C800 with supplementation of 400, 500, 600 and 800 mg AA kg(-1). Fish fed 800 mg AA kg(-1) supplemented diets presented greater weight gain and survival. Hematocrit, hemoglobin concentrations and erythrocytes showed significant increase (p<0.05) in C600 and C800 relatively to the others. Total leukocyte values were significantly higher in fish fed vitamin C supplemented diets relatively to those fed RD and leukocytes count of C600 and C800 were the highest among the treatments. Monocytes were the only cells of fish defense mechanism that presented variation, and C600 and C800 presented the lowest values (P<0.05). Glucose level was significantly different relatively to RD only in C400 and the plasmatic total protein values for fish fed vitamin C supplemented diets were higher than for fish fed the RD. Fish plasmatic ions (Na(+) and Cl(-)) were significantly lower for C500, C600 and C800 relatively to C400 and RD. The physiological profile and the growth performance of matrinx? suggest that diet supplemented with 800 mg AA kg(-1) can improve its performance and increase the survival rate.     

Estimation of activity of pharmakopeal disinfectants and antiseptics against Gram-negative and Gram-positive bacteria isolated from clinical specimens, drugs and environment

The MIC of nine different disinfectants and antiseptics were determined for the Gram-negative and Gram-positive bacteria. Strains originated from clinical specimens, drugs and environment. A sensitivity was determined against chlorhexidinum digluconate (Gram-negative: 0,625-80 mg/L, Gram-positive: 0,3-10 mg/L), benzalconium chloride (Gram-negative: 2,5-1280 mg/L, Gram-positive: 1,25-20 mg/L), salicilic acid (Gram-negative and Gram-positive: 400-1600 mg/L), benzoic acid (Gram-negative: 800-1600 mg/L, Gram-positive: 400-1 600 mg/L), boric acid (Gram-negative: 800-12 800 mg/L, Gram-positive: 1 600-6400 mg/L), chloramine B (Gram-negative: 1600-6400 mg/L, Gram-positive:800- 6400 mg/L), jodine (Gram-negative: 200-1600 mg/L, Gram-positive: 200-1600 mg/L), etacridine lactate (Gram-negative: 40 do > 20480 mg/L, Gram-positive: 40-1280 mg/L) and resorcine (Gram-negative: 1600-6400 mg/L, Gram-positive: 800-6400 mg/L). Diversified values of MIC for different strains were obtained, especially in the case of benzalconium chloride, etacridine lactate, chlorhexidinum digluconate, boric acid and iodine. Strains isolated from environment were usually more susceptible to examined compounds than clinical strains. The biggest diversification of sensitivity was observed among strains originated from drugs where besides sensitive appeared strains characterizing by very high MIC values of some substances, eg. boric acid.     

Effects of dietary pyridoxine on immune responses in abalone, Haliotis discus hannai Ino

A feeding experiment was conducted to investigate the effects of dietary pyridoxine (PN) on the immune responses of abalone, Haliotis discus hannai Ino. Purified diets supplemented with 0, 40, 800 mg PN kg(-1) or 80 mg kg(-1) of 4-deoxypyridoxine (PN antagonist) were fed to adult abalone (initial weight 45.77 +/- 0.25 g; initial shell length 68.02 +/- 0.78 mm) for 90 days. The air-dried brown kelp, Laminaria japonica, was used as a control diet. Each diet was fed to three replicate groups of abalone in a recirculation system using a completely randomised design. The results showed that weight gain ratio (WGR) of the abalone generally increased with the level of dietary PN supplementation though no significant differences were found among the treatments (P > 0.05). Phagocytic and phenoloxidase activities were significantly higher in abalone fed diets supplemented with 800 mg PN kg(-1) than those fed the PN-free diet or the one with 4-deoxypyridoxine (P < 0.05). Agglutination titre and respiratory burst activity were significantly higher in abalone fed diets supplemented with 40 mg PN kg(-1) than those fed the PN-free diet or the one with 4-deoxypyridoxine (P < 0.05). There were no significant differences in immunological characteristics between the abalone fed the diet containing 40 mg PN kg(-1) and those fed the diet containing 800 mg PN kg(-1) (P > 0.05). L. japonica resulted in significantly lower agglutination titre, respiratory burst and phagocytic activities than the artificial diets supplemented with 40 or 800 mg PN kg(-1) (P < 0.05). Total haemocyte count (THC), serum protein concentration, and the activities of lysozyme and acid phosphatase were not significantly affected by the dietary treatments (P > 0.05). These results demonstrate that dietary deficiency of pyridoxine suppresses the immune functions in H. discus hannai, and further investigations are needed to optimise the dietary level of this vitamin for maintaining the best immune responses in abalone.     

Studies on the origin of the near-infrared (800-900 nm) absorption of cytochrome c oxidase

Data are presented which were collected in the course of the past ten years and bear on the correlation of absorbance at 800 nm and the EPR signal at g = 2 ('copper signal') of cytochrome c oxidase in various states of oxidation and ligation. Both EPR and optical reflectance spectra were obtained at low temperature (-170 to -190 degrees C). For some sets of samples spectra were recorded in the range 500-1100 nm. A particular efFort was made to study this correlation with what are called 'mixed valence' states (Greenwood, C., Wilson, M.T. and Brunori, M. (1974) Biochem. J. 137, 205-215), when cytochrome a and the EPR-detectable copper are thought to be oxidized and the other components reduced and vice versa. These data show no evidence that the copper component of cytochrome oxidase which has so far not been detected by EPR makes a contribution to the absorption between 800 and 900 nm exceeding 10-15% of the total, which is close to or within the error of the respective measurements. For the various states of the oxidase examined in this work the 700-800 nm region did not appear to be more useful than the 800-900 nm region for determining the state of the EPR-undetectable copper in a reliable way. These conclusions are in agreement with results presented previously from other laboratories concerning the relationship of optical (approx. 800 nm) and EPR spectroscopic (g = 2) data obtained with the enzyme.     

Presence de deux types de microstructure chezArchaeocyathus atlanticus BILLINGS (Cambrien inferieur,Labrador, Canada)

Ultra-thin sections studied by optical microscope as well as polished surfaces observed by scanning, unquestionably show that two types of secretion coexist in the skeleton of Archaeocyathus atlanticus BILLINGS - Taylor's Gulch (Labrador, Canada) - one characterizing the taeniae (pseudo-septa), the other the vesicular tissue (dissepiments).     

Changes in the content of pigment-protein complexes in Rhodobacter sphaeroides forma sp. denitrificans grown under photosynthetic and photo-denitrifying conditions

Changes in the relative content of pigment-protein complexes, RC-B880 and B800-850, were studied in membranes of Rhodobacter sphaeroides forma sp. denitrificans cultured under various anaerobic conditions. The content of each pigment-protein complex was determined by the decomposition of the absorption spectra of membranes in the near-infrared region into the spectra of RC-B880 and B800-850. The standard spectrum of each complex in the membranes was obtained using two absorption spectra of membranes with different ratios of the complexes by eliminating the spectrum of first one than the other complex. Spectra composed from the two standard spectra were in good agreement with original membrane spectra after subtraction of the contribution of scattering in various membrane samples. Bacteriochlorophyll (BChl) content in the membrane was dependent on the light intensity during growth. The relation between the total BChl content in the membrane and BChl content in the RC-B880 and B800-850 complex was linear above 15 nmol BChl per mg membrane protein, regardless of the culturel conditions, photosynthetic or photo-denitrifying. The linear relationship reached a point where all BChl molecules were contained in RC-B880 at 13 nmol BChl per mg membrane protein. This means that only RC-B880 would be synthesized below the threshold, and above the threshold additional BChl was distributed between RC-B880 and B800-850 in a constant ratio (1:5.7). The results suggest that the syntheses of B800-850 and RC-B880 are not regulated independently.     

Effect of illumination intensity and inhibition of carotenoid biosynthesis on assembly of peripheral light-harvesting complexes in purple sulfur bacteria <Emphasis Type="Italic">Allochromatium vinosum</Emphasis> ATCC 17899

Effect of illumination intensity and inhibition of carotenoid biosynthesis on assemblage of different spectral types of LH2 complexes in a purple sulfur bacterium Allochromatium (Alc.) vinosum ATCC 17899 was studied. Under illumination of 1200 and 500 lx, the complexes B800-850 and B800-840 and B800-820 were assembled. While rhodopine was the major carotenoid in all spectral types of the LH2 complex, a certain increase in the content of carotenoids with higher numbers of conjugated double bonds (anhydrorhodovibrin and didehydrorhodopin) was observed in the B800-820 complex. At 1200 lx, the cells grew slowly at diphenylamine (DPA) concentrations not exceeding 53 μM, while at illumination intensity decreased to 500 lx they could grow at 71 μM DPA (DPA cells). Independent on illumination level, the inhibitor is supposed to impair the functioning of phytoene synthetase (resulting in a decrease in the total carotenoid content) and of phytoene desaturase, which results in formation of neurosporene hydroxy derivatives and ζ-carotene. In the cells grown at 500 lx, small amounts of spheroidene and OH-spheroidene were detected. These carotenoids were originally found under conditions of carotenoid synthesis inhibition in bacteria with spirilloxanthin as the major carotenoid. Carotenoid content in the LH2 complexes isolated from the DPA cells was ~15% of the control (without inhibition) for the B800-850 and ~20% of the control for the B800-820 and B800-840 DPA complexes. Compared to the DPA pigment-containing membranes, the DPA complexes were enriched with carotenoids due to disintegration of some carotenoidless complexes in the course of isolation. These results support the supposition that some of the B800-820, B800-840, and B800-850 complexes may be assembled in the cells of Alc. vinosum ATCC 17899 without carotenoids. Comparison of the characteristics obtained for Alc. vinosum ATCC 17899 and the literature data on strain D of the same bacteria shows that they belong to two different strains, rather than to one as was previously supposed.     

Characterisation of the LH2 spectral variants produced by the photosynthetic purple sulphur bacterium Allochromatium vinosum

This study systematically investigated the different types of LH2 produced by Allochromatium (Alc.) vinosum, a photosynthetic purple sulphur bacterium, in response to variations in growth conditions. Three different spectral forms of LH2 were isolated and purified, the B800-820, B800-840 and B800-850 LH2 types, all of which exhibit an unusual split 800 peak in their low temperature absorption spectra. However, it is likely that more forms are also present. Relatively more B800-820 and B800-840 are produced under low light conditions, while relatively more B800-850 is produced under high light conditions. Polypeptide compositions of the three different LH2 types were determined by a combination of HPLC and TOF/MS. The B800-820, B800-840 and B800-850 LH2 types all have a heterogeneous polypeptide composition, containing multiple types of both α and β polypeptides, and differ in their precise polypeptide composition. They all have a mixed carotenoid composition, containing carotenoids of the spirilloxanthin series. In all cases the most abundant carotenoid is rhodopin; however, there is a shift towards carotenoids with a higher conjugation number in LH2 complexes produced under low light conditions. CD spectroscopy, together with the polypeptide analysis, demonstrates that these Alc. vinosum LH2 complexes are more closely related to the LH2 complex from Phs. molischianum than they are to the LH2 complexes from Rps. acidophila.     

mtDNA variation in Inuit populations of Greenland and Canada: migration history and population structure

We examined 395 mtDNA control-region sequences from Greenlandic Inuit and Canadian Kitikmeot Inuit with the aim of shedding light on the migration history that underlies the present geographic patterns of genetic variation at this locus in the Arctic. In line with previous studies, we found that Inuit populations carry only sequences belonging to haplotype clusters A2 and D3. However, a comparison of Arctic populations from Siberia, Canada, and Greenland revealed considerable differences in the frequencies of these haplotypes. Moreover, large sample sizes and regional information about birthplaces of maternal grandmothers permitted the detection of notable differences in the distribution of haplotypes among subpopulations within Greenland. Our results cast doubt on the prevailing hypothesis that contemporary Inuit trace their all of their ancestry to so-called Thule groups that expanded from Alaska about 800-1,000 years ago. In particular, discrepancies in mutational divergence between the Inuit populations and their putative source mtDNA pool in Siberia/Alaska for the two predominant haplotype clusters, A2a and A2b, are more consistent with the possibility that expanding Thule groups encountered and interbred with existing Dorset populations in Canada and Greenland.     

FAO/UNESCO/WMO agroclimatology survey of a semi-arid area south of the Sahara

This agroclimatic survey was the second undertaken jointly by FAO, UNESCO and WMO. The first was undertaken in the semi-arid zones of Jordan, Lebanon, Syria, Iraq and Iran (1), (2). The second survey was started in 1963 and involved a belt of territory in West Africa 4,000 km long and up to 800 km wide, bounded on the west by the Atlantic Ocean and on the east by the border between the republics of Chad and the Sudan. The zone lies roughly between 12° and 20° north latitude and includes parts of Senegal, Mauritania, Mali, Upper Volta, Ghana, Togo, Dahomey, Niger, Nigeria, Cameroon and Chad.Summary prepared by G.W.Robertson, Canada Department of Agriculture,Ottawa, from a report by J.Cochemé published under the same title in Nature and Resources (Unesco), Vol. 2, number 4, 1–10, 1966.     

Bone fluoride concentrations in beluga whales from Canada

Beluga whales (Delphinapterus leucas) from the St. Lawrence Estuary have been reported to have dental and bone abnormalities. To determine whether these lesions could be caused by high exposure to fluorides, we measured bone fluoride levels in eight beluga whales stranded on the shores of the St. Lawrence Estuary (Quebec, Canada), and in nine beluga whales killed by Inuit hunters in the Hudson Bay (North Western Territories, Canada). In both groups, fluoride concentrations were higher than those found in terrestrial mammals intoxicated by fluorides. Unexpectedly, fluoride concentration was significantly higher in beluga whales from the Hudson Bay (mean +/- SD: 10.365 +/- 1.098 ppm) than in beluga whales from the St. Lawrence Estuary (4.539 +/- 875 ppm) and was positively correlated with age in the latter population. Differences in diet might explain the differences in fluoride concentrations found between these two populations.     

Self-association of the neuroregulatory peptide substance P and its C-terminal sequences

Self-association of substance P and its C-terminal partial peptide sequences was studied by CD, quasi-electric light scattering, and sedimentation experiments. CD spectra of these peptides are strongly influenced by self-association. They exhibit strong characteristic negative ellipticities, suggesting the formation of a presumably B-type ordered structure. The tendency to form multimers depends on chain length and constitution and has its maximum at the octapeptide (SP 8). The peptide multimers have a broad distribution of sizes in the range of 30- and 800-nm diameter. Subdivision of this distribution into two size classes gives mean diameters of 60–100 nm (predominating)/200–800 nm for substance P and 30–50 nm/200–800 nm for SP 8 multimers.     

Projected estimates of cancer in Canada in 2022

Background:Regular cancer surveillance is crucial for understanding where progress is being made and where more must be done. We sought to provide an overview of the expected burden of cancer in Canada in 2022.Methods:We obtained data on new cancer incidence from the National Cancer Incidence Reporting System (1984–1991) and Canadian Cancer Registry (1992–2018). Mortality data (1984–2019) were obtained from the Canadian Vital Statistics — Death Database. We projected cancer incidence and mortality counts and rates to 2022 for 22 cancer types by sex and province or territory. Rates were age standardized to the 2011 Canadian standard population.Results:An estimated 233 900 new cancer cases and 85 100 cancer deaths are expected in Canada in 2022. We expect the most commonly diagnosed cancers to be lung overall (30 000), breast in females (28 600) and prostate in males (24 600). We also expect lung cancer to be the leading cause of cancer death, accounting for 24.3% of all cancer deaths, followed by colorectal (11.0%), pancreatic (6.7%) and breast cancers (6.5%). Incidence and mortality rates are generally expected to be higher in the eastern provinces of Canada than the western provinces.Interpretation:Although overall cancer rates are declining, the number of cases and deaths continues to climb, owing to population growth and the aging population. The projected high burden of lung cancer indicates a need for increased tobacco control and improvements in early detection and treatment. Success in breast and colorectal cancer screening and treatment likely account for the continued decline in their burden. The limited progress in early detection and new treatments for pancreatic cancer explains why it is expected to be the third leading cause of cancer death in Canada.

The impact of cancer on the Canadian population and health care systems is substantial. Cancer is the leading cause of death in Canada^1,2 and previous estimates have shown that 43% of all people in Canada are expected to receive a cancer diagnosis in their lifetime.³ With an aging and growing population, the number of new cancer cases and deaths in Canada is also increasing.⁴ In addition to its impact on health, cancer is costly. The economic burden of cancer care in Canada rose from $2.9 billion in 2005 to $7.5 billion in 2012, annually.⁵Given the considerable health and economic impact of cancer in Canada, comprehensive and reliable surveillance information is necessary for identifying where progress has been made and where more attention and resources are needed. To meet these needs, the Canadian Cancer Statistics Advisory Committee, in collaboration with the Canadian Cancer Society, Statistics Canada and the Public Health Agency of Canada, produces the latest surveillance statistics on cancer in Canada.Cancer data often lag the current date by several years, owing to the time associated with collecting, verifying and analyzing the data. Short-term cancer incidence and mortality rates can be projected by extrapolating past trends to estimate future trends, using statistical models. These short-term projections provide a more up-to-date estimate of the cancer landscape in Canada. Incidence and mortality counts, along with age-standardized rates, provide a picture of the impact of cancer in Canada, which is essential for resource planning, research and informing cancer-control programs.Canadian Cancer Statistics 2021³ provided detailed estimates of cancer incidence, mortality and survival in Canada by age, sex, geographic region and over time for 22 cancer types.³ Here, we provide updated estimates of the counts and age-standardized rates of new cancer cases (incidence) and cancer deaths (mortality) expected in 2022 by sex and province and territory, for all ages combined.     

The carbon footprint of bread

Background, aim, and scope  

The aim of this study has been to estimate the carbon footprint of bread produced and consumed in the UK. Sliced white and wholemeal bread has been considered for these purposes and the functional unit is defined as “one loaf of sliced bread (800 g) consumed at home”. The influence on the carbon footprint of several parameters has been analysed, including country of origin of wheat (UK, Canada, France, Germany, Spain and USA), type of flour (white, brown and wholemeal) and type of packaging (plastic and paper bags). The effect on the results of the type of data (primary and secondary) has also been considered.