PubMed Health⌕ Search

Biomedical subjects

G Samuelsson

Publications and source records attributed to G Samuelsson.

At least 73 records · Page 4Linked to original sources
PubMed1985

Photoinhibition and Reactivation of Photosynthesis in the Cyanobacterium Anacystis nidulans.

The susceptibility of photosynthesis to photoinhibition and its recovery were studied on cultures of the cyanobacterium Anacystis nidulans. Oxygen evolution and low temperature fluorescence kinetics were measured. Upon exposure to high light A. nidulans showed a rapid decrease in oxygen evolution followed by a quasi steady state rate of photosynthesis. This quasi steady state rate decreased with increasing photon flux density of the photoinhibitory light. Reactivation of photosynthesis in dim light after the photoinhibitory treatment was rapid: 85 to 95% recovery occurred within 2 hours. In the presence of the translation inhibitor, streptomycin (250 micrograms per milliliter), no reactivation occurred. We also found that the damage increased dramatically if the high light treatment was done with streptomycin added. A transcription inhibitor, rifampicin, did not inhibit the reactivation process. Based on these data we conclude that the photoinhibitory damage observed is the net result of a balance between the photoinhibitory process and the operation of the repairing mechanism(s).

Journal Article↗
PubMed1985

Urinary tract infection in children with type I diabetes.

The prevalence and incidence of bacteriuria in 304 girls and 337 boys with type I diabetes was studied by screening for bacteriuria at their regular outpatient controls. In 90 girls and 108 boys a urine specimen was sampled every third month during a year. The prevalence of bacteriuria was 3/304 in girls and 0/337 in boys. During the one year follow-up one of the 90 girls had pyelonephritis and two cystitis while none of the boys had bacteriuria. It is concluded that the rate of urinary tract infection in young diabetic persons does not differ from that present in healthy young people.

Adolescent↗
PubMed1983

Inventory of plants used in traditional medicine in Tanzania. II. Plants of the families Dilleniaceae--Opiliaceae.

Forty five plants are listed, which are used by traditional healers in the northeastern part of Tanzania. For each species are given: the botanical name with synonyms, vernacular name, collection number, locality, habitus, approximate distribution and medical use. Results of a literature survey are also reported, including medical use, isolated constituents and pharmacological effects.

Humans↗
PubMed1983

Inventory of plants used in traditional medicine in Tanzania. Part III. Plants of the families Papilionaceae-Vitaceae.

Forty-six plants are listed, which are used by traditional healers in the northeastern part of Tanzania. For each species are given: the botanical name with synonyms; vernacular name; collection number; locality; habitus; approximate distribution and medical use. Results of a literature survey are also reported, including medical use, isolated constituents and pharmacological effects.

Phytotherapy↗
PubMed1983

Changes in Photosystem II Account for the Circadian Rhythm in Photosynthesis in Gonyaulax polyedra.

Cell-free extracts that show activity in photosynthetic electron flow have been prepared from the unicellular dinoflagellate, Gonyaulax polyedra. Electron flow, as O(2) uptake, was measured through both photo-system I and II from water to methyl viologen, through photosystem I alone from reduced 2,6-dichlorophenol indophenol to methyl viologen which does not include the plastoquinone pool or from duroquinol to methyl viologen which includes the plastoquinone pool. Electron flow principally through photosystem II was measured from water to diaminodurene and ferricyanide, as O(2) evolution. Cultures of Gonyaulax were grown on a 12-hour light:12 hour dark cycle to late log phase, then transferred to constant light at the beginning of a light period. After 3 days, measurements of electron flow were made at the maximum and minimum of the photosynthetic rhythm, as determined from measurements of the rhythm of bioluminescence. Photosynthesis was also measured in whole cells, either as (14)C fixation or O(2) evolution. Electron flow through both photosystems and through photosystem II alone were clearly rhythmic, while electron flow through photosystem I, including or excluding the plastoquinone pool, was constant with time in the circadian cycle. Thus, only changes in photosystem II account for the photosynthesis rhythm in Gonyaulax.

Journal Article↗
PubMed1982

Inventory of plants used in traditional medicine in Tanzania. I. Plants of the families Acanthaceae-Cucurbitaceae.

Sixty-two plants are listed, which are used by traditional healers in the northeastern part of Tanzania. For each species are given: the botanical name with synonyms, vernacular name, collection number, locality, habitus, approximate distribution, and medical use. Results of a literature survey are also reported, including medical use, isolated constituents and pharmacological effects.

Humans↗
PubMed1982

The incidence of diabetes mellitus in Swedish children 0-14 years of age. A prospective study 1977-1980.

This is a prospective study of the incidence of insulin-dependent diabetes mellitus (IDDM) in children 0-14 years of age, including all newly diagnosed cases in the whole of Sweden from July 1, 1977 until June 30, 1980. All 45 Swedish departments of paediatrics participated. During the three-year-period studied, 1108 Swedish children, 0-14 years of age had their onset of diabetes. That means around 369 new diabetics yearly in the age groups studied. The mean yearly incidences in the years 1977-80 were 22.6, 22.8 and 22.6 per 100000 children, respectively. Mean prevalence on June 30, 1980 and 1.48 per 1000 children 0-14 years with a wide range of 0.71-2.65. The age distribution at onset showed a gradual increase and peak incidences at 11 years of age for the girls and 4 and 13 years of age for the boys. There was a consistently higher incidence for boys in the younger age groups during the three-year-period studied. Peak incidences of new cases were reached in January, March and July through October for the age groups 5-9 and 10-14 years of age. No such seasonal variation was seen for children 0-4 years of age. The cumulative incidence of IDDM at 14 years of age was 3.2 per 1000 for the boys and 2.9 per 1000 for the girls. The degree of ascertainment in this study was 93.4%.

Adolescent↗
PubMed1981

IgG F(ab')2 of rabbit anti-M sera but not the unfractionated sera are bactericidal for some group A streptococci with IgG Fc-receptor activity. Opsonic effect ascribable to anti-IgG.

We have earlier reported on a group A streptococcal strain, type M12, which upon serial mouse passage acquired IgG Fc-receptor activity but lost the M-antigen. The passaged strain, 12P, was highly virulent for mice and grew well in normal human blood. The present study particularly concerns the opsonic effect on 12P of rabbit anti-M3, anti-M12 and anti-12P sera, as well as the corresponding IgG F(ab')2. Indirect bactericidal tests showed that the homologous anti-12P seum and IgG F(ab')2 were opsonic. The anti-M3 and anti-M12 had no effect on 12P; surprisingly, however, IgG F(ab')2 isolated from these sera displayed a clearcut opsonic activity. Data are presented which indicate that these "paradoxical" results can be explained by the binding of IgG F(ab')2 with anti-IgG specificity to human IgG, linked to the streptococcal surface through Fc-receptors. Only anti-12P serum, or IgG F(ab')2, were protective for mice on challenge with strain 12P.

Animals↗
PubMed1981

IgG-Fc-receptors in T-type 12 group A streptococci from clinical specimens: absence from M-type 12 and presence in M-type 22.

Eighty-eight T-type 12 group A streptococcal strains were randomly selected from routine specimens in two epidemiologically unrelated districts. All of 26 M-type 12 strains lacked IgA and IgG Fc-receptors, whereas all 32 M-type 22 strains had IgG Fc-receptors and 20 of them also receptors for IgA Fc. The remaining strains were not further M-typed but 18 of these 30 strains exhibited receptors for IgG and 13 for IgA.

Humans↗
PubMed1980

Demonstration of separate receptors for human IgA and IgG in group A streptococci type 4. Separation of the solubilized receptors from group- and type-specific antigens, lipoteichoic acid and peptidoglycan.

The alkaline extract of group A streptococci type 4 was separated by electrophoresis and diffused against 27 normal human sera. One of the precipitates appeared with 85% of the sear. Addition of purified IgA myeloma protein or sera containing IgA M-components to the extract changed the electrophoretic mobility of the precipitate anodically. Purified IgG Fc-fragments or sera containing IgG M-component did not affect the mobility of the precipitate. It was concluded that this precipitate contained the streptococcal receptor for human IgA. A non-precipitating IgG Fc-receptor, with agglutinating capacity for cells coated with human IgG1 but not IgG3, was localized by preparative electrophoresis to the same electrophoretic region as the IgA receptor. The mobility of the IgG receptor remained unaltered on addition of IgA myeloma protein permitting a separation of the two receptors by preparative electrophoresis. The receptors were distinct from the group specific carbohydrate, peptidoglycan and lipoteicholic acid. No M antigen or opacity factor were demonstrated in the extract.

Antigens, Viral↗
PubMed1980

Changes in virulence, M protein and IgG Fc receptor activity in a type 12 group A streptococcal strain during mouse passages.

A type 12 group A strain (1800) was passaged serially through mice 25 times. The ability to servive in normal human blood dropped from a growth index of 52 after the first passage to 1 after four passages. After 14 passages the growth index increased again and stabilized above 30. The virulence for mice increased from a LD100 of 10(8) colony forming units (CFU) to 10-100 CFU after 7 passages and then remained constant. The Mqw antigen disappeared after 4 passages as tested by immunodiffusion, electroimmunoassay and indirect bactericidal tests. Three antisera, raised in rabbits against strains originally belonging to types M3, M12 and M46 but devoid of type antigens after mouse passages showed high bactericidal indices against the 1800 strain after 14 or more passages on mice. Anti-type M1 serum was also found bactericidal for the passaged strains. The IgG Fc-receptor activity of the strain isolated after each mouse passage was tested in hemagglutination experiments with human red blood cells coated with "incomplete" anti-Rh and hot hydrochloric acid extracts of the strains. The capacity to agglutinate "Ripley"-coated cells increased gradually during the first 12 passages and subsequently the titres of the extracts stabilized between 1:160 and 1:320. The HUN coat, useful for detection of the G3m (5) maraker gave titraes increasing with the number of passages while the titres for IgG1 coats kept at 1:4 or below. On background of these results, the possible role of the IgG Fc-receptor as a virulence factor is discussed.

Animals↗
PubMed1979

Interaction of the Fc part of IgG with Lancefield extracts of hemolytic streptococci. Strain specificity and activity.

Lancefield extracts of 19 types of group A streptococci as well as one group C and one group G strain were examined for agglutination of human red cells coated with various anti-Rh antibodies. Fourteen extracts agglutinated one or more of the coated cell samples, while five did not. The agglutination was inhibited by Fc but not by Fab fragments of human IgG. After mouse passages, three of the non-agglutinating strains acquired agglutinating capacity. At least three different reactivities were distinguished by the action of the extracts on IgG1 and IgG3 coated cells, respectively. Two of the streptococcal extracts, agglutinating the same anti-Rh coated cells, could be further differentiated in hemagglutination inhibition (HAI) experiments using purified IgG3 myeloma proteins. Five selected agglutinating systems were inhibited by purified myeloma proteins of the IgG1, IgG2, and IgG4 subclasses. IgG3 proteins inhibited only two of the five HAI systems.

Antibodies, Bacterial↗