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A Sandström

Publications and source records attributed to A Sandström.

At least 55 records · Page 3Linked to original sources
PubMed1990

Structure of a hepatotoxic pentapeptide from the cyanobacterium Nodularia spumigena.

The structure of a hepatotoxic peptide from the cyanobacterium Nodularia spumigena was determined using 1D and 2D proton nuclear magnetic resonance spectroscopy and fast atom bombardment mass spectrometry. The toxin was a cyclic pentapeptide (mol. wt 824.5) with the structure cyclo-(beta-methylisoAsp-Arg-Adda-isoGlu-N-methylde hydrobutyric acid) (Adda: 3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid).

Amino Acid Sequence↗
PubMed1990

Prevalence of HIV-1 infection in the Kagera region of Tanzania: a population-based study.

A population-based survey was carried out in the Kagera region of the United Republic of Tanzania in 1987 to determine the magnitude of HIV-1 infection and to study associated risk factors. The region was divided into one urban and three rural zones. A multistage cluster sampling technique was adopted. Antibodies to HIV-1 were determined by enzyme-linked immunosorbent assay and confirmed by Western blot analysis. A total of 2,475 adults (aged 15-54 years) and 1,961 children (aged 0-14 years) was studied. The overall prevalence of HIV-1 infection among adults was 9.6%, with a higher prevalence in the urban zone (24.2%) than in the three rural zones (10.0, 4.5 and 0.4%, respectively). The corresponding figures for children were 1.3% overall: 3.9% in the urban area and for the rural areas 1.2, 0.8 and 0.0%, respectively. The age-specific seroprevalence for adults was highest in the age group 25-34 years. The age-standardized sex-specific prevalence was higher among women than men in the urban zone, while it was the same in the rural zones. Change of sexual partners among adults was associated with an increased risk of HIV-1 seropositivity. Travelling outside the region but within the country was also found to be associated with increased risk of HIV-1 infection but only in the rural population.

Adolescent↗
PubMed1990

Epidemiology of HIV infections. Design options with special reference to developing countries.

Health research and planning need valid data for decision making. In a developing country cost-effectiveness in research design is of special significance. In such situations, population-based data are needed. This paper reviews the literature on HIV/AIDS studies published during 1982-88 with respect to epidemiological methods and study designs and with special relevance to developing countries. A methodological taxonomy is presented based on this review illustrating the special need for analytic epidemiology. The paper also presents experiences and results from an ongoing collaborative project on HIV infections between Tanzanian and Swedish researchers. The project, which was launched in 1987 in the Kagera region where the first AIDS cases were seen in 1983, applies both epidemiological and behavioural methods.

Acquired Immunodeficiency Syndrome↗
PubMed1989

The Swedish childhood diabetes study--results from a nine year case register and a one year case-referent study indicating that type 1 (insulin-dependent) diabetes mellitus is associated with both type 2 (non-insulin-dependent) diabetes mellitus and autoimmune disorders.

From July 1, 1977 to July 1, 1986, 3,503 incident cases of Type 1 (insulin-dependent) diabetes mellitus were registered in the Swedish childhood diabetes study. Using data from this register and from a case-referent study, including all incident Type 1 diabetic children in Sweden during one year and, for each patient, two referent children matched according to age, sex and county, we have studied the associations between Type 1 diabetes and familial Type 1 and Type 2 (non-insulin-dependent) diabetes, thyroid, adrenal, allergic, rheumatic, heart and bowel disease. The mean annual incidence per 100,000 during the nine year period was 25.1 for boys and 23.5 for girls. In 8.5% of the patients, one parent had Type 1 diabetes, 73% of whom were fathers. Fifty-six of the patients (1.7%) had a parent with Type 2 diabetes. The prevalence of parental Type 1 diabetes tended to be higher in patients with younger age at onset; whereas, the opposite was found for patients with parental Type 2 diabetes. In the case-referent study, the age-adjusted odds ratio for Type 1 diabetes when a first and/or second degree relative had Type 1 diabetes was 5.5 (95% confidence limits 4.0-7.7), and in accordance with the findings of the case register, the odds ratio tended to be highest in patients with the youngest age at onset. Season at onset of the patients was not associated with parental Type 1 diabetes. The odds ratio for Type 1 diabetes was significantly increased 3.3 (95% confidence limits: 2.3-4.6) when Type 2 diabetes was reported in relatives (three generations).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

The Swedish childhood diabetes study--social and perinatal determinants for diabetes in childhood.

Using the Swedish childhood diabetes register, a nationwide, case-referent study was performed from September 1, 1985 to August 31, 1986. Based on the information from a mailed questionnaire sent to all incident diabetic children and for each diabetic child - two referent children matched according to age, sex, and county, we have analysed perinatal events and aspects of the social environment as possible risk factors for Type 1 (insulin-dependent) diabetes in childhood. A significantly larger proportion of the mothers of the diabetic children were older than 40 years compared to those of the referent children (33% and 24%, p = 0.01 respectively). A smaller percentage of mothers of the diabetic children had a high educational level compared to mothers of referent children (10% and 15%, p = 0.03 respectively) and 39% of the fathers of the diabetic children were manual workers compared to 31% of the fathers of referent children (p = 0.03). Perinatal events did not differ between diabetic and referent children. In children 0-6 years, the duration of breast-feeding was significantly shorter in diabetic children than among referent children (median duration for diabetic children 5 months compared to 6 months for referent children p = 0.03). When considering the presence of Type 1 diabetes among relatives, maternal age over 40 years, low educational level of the mother, and the father being a manual worker as risk factors, the presence of 1 to 4 of any of these risk factors increased the relative risk for Type 1 diabetes cumulatively from 1.2-7.5.(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗
PubMed1989

Structure and toxicity of a peptide hepatotoxin from the cyanobacterium Oscillatoria agardhii.

A peptide hepatotoxin was isolated by reversed phase liquid chromatography from the cyanobacterium Oscillatoria agardhii and characterized structurally and toxicologically. Amino acid analyses, proton nuclear magnetic resonance and fast atom bombardment mass spectrometry showed that the toxin is a cyclic heptapeptide (mol. wt 1023.5) with the structure cyclo-(Ala-Arg-Asp-Arg-Adda-Glu-N-methyldehydroAla) (Adda: 3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid). In mice the toxic effects were restricted mainly to the liver where the toxin induced massive hemorrhages and a disruption of the lobular and sinusoidal structure. The i.p. LD50 of the toxin was 250 micrograms/kg. The structural and toxic properties of this peptide are very close to those of microcystins, cyclic peptide toxins produced by the cyanobacterium Microcystis aeruginosa.

Amino Acid Sequence↗
PubMed1989

Why do all lariat RNA introns have adenosine as the branch-point nucleotide? Conformational study of naturally-occurring branched trinucleotides and its eleven analogues by 1H-, 31P-NMR and CD spectroscopy.

1H-NMR conformational studies of six branched triribonucleotides where the branch-point nucleotide was either U, C or G (4-9) have been carried out by assigning 1H resonances through 2D NMR and then observing the temperature-dependent (i) chemical shifts of the aromatic and the anomeric protons, and (ii) shifts of the equilibrium of N and S pseudorotamer populations of each sugar moiety. The data have been compared with those of 2'----5' dimers (1-3) and other branched trimers (10-16). It emerged that all the branched trimers (4-16) adopt a conformational state closer to the corresponding 2'----5' dimers than the corresponding 3'----5' dimers. A temperature-dependent 31P chemical shift study confirmed that the conformational constraint is mainly associated with the 2'----5' phosphate linkage. Although, it appeared with the CD data that when C or especially when U is at the branch-point the overall constraint is weak. This suggests that even if these trimers adopt a 2'----5' dimer geometry, there is a lack of stabilization by strong stackings within the molecule. This is in sharp contrast with the results found for A (10-16) and to a smaller extent for G (8, 9) at the branch-point.

Adenosine↗
PubMed1988

Kinetics, anion binding and mechanism of Co(II)-substituted bovine muscle carbonic anhydrase.

The binding of N3- to Co(II)-substituted bovine carbonic anhydrase III was measured at various pH values by spectrophotometric titrations. The apparent Ki values were found to increase with pH in the studied range between pH 5.8 and 8.9. The inhibition of CO2 hydration by N-3 was found to be essentially uncompetitive at all investigated pH values (pH 6.3-8.9). The Ki values for the inhibition of kcat are much smaller than those obtained in the spectrophotometric titrations indicating that an enzyme form with a high affinity for N-3, presumably having a metal-bound H2O, accumulates in the steady state at saturating CO2 concentrations. Assuming that the low pH limit of Ki = 9 microM for the inhibition of kcat represents the affinity of N-3 for the Co(II)-OH2 form, a pKa value near 5 can be estimated for Co(II)-bound water from the pH dependence of N-3 binding in the absence of CO2. Measurements of time-resolved absorption spectra during CO2 hydration in the presence of a low N-3 concentration showed the transient appearance of the characteristic spectrum of the enzyme-N-3 adduct clearly demonstrating the accumulation in the steady state of an enzyme form with a high affinity for N-3. In similar experiments without inhibitor the transient formation of a spectral form corresponding to a Co(II)-OH2 species has been demonstrated. This spectral form is rather featureless lacking the absorption maxima at 618 nm and 640 nm characteristic of the Co(II)-OH- species. Our results strongly support the hypothesis that the rate-limiting step in CO2 hydration catalyzed by carbonic anhydrase III is the protolysis of metal-bound water.

Animals↗
PubMed1988

Prognosis in bilateral breast cancer. Effects of time interval between first and second primary tumours.

Survival rates for 67 women with bilateral breast cancer were compared to those for 1282 women with unilateral disease in a follow-up of 1349 women participating in a population-based study. Relative survival at 8 years of follow-up was 69% for women with unilateral disease as compared to 53% for women with bilateral cancer. When possible confounding histopathological differences--data about which were prospectively collected--and age were adjusted for in a multivariate analysis, the relative hazard rate was significantly higher for women with bilateral versus unilateral breast cancer (P = 0.006). The impact of interval time between the two primaries was analysed and a roughly two-fold higher hazard rate was seen for synchronous cancers with regularly falling risk for increasing interval times. This trend was however not statistically significant. The results indicate that the two tumours contribute independently to the patient's excess risk of dying and thus occur as two seemingly biologically unrelated events with respect to the tumour-host relationship and metastatic behaviour.

Aged↗
PubMed1988

Prognostic significance of the Ackerman classification and other histopathological characteristics in breast cancer. An analysis of 1,349 consecutive cases with complete follow-up over seven years.

Survival rates during a follow-up period of more than seven years were analyzed in 1,349 women with breast cancer in relation to the histo-pathological classification of female breast cancer proposed by Ackerman and to other commonly used histo-pathological criteria, including the axillary node status. The information was collected prospectively during a case-control study. Major emphasis was placed on multivariate evaluation. In analyses based on the histo-pathological findings in the mastectomy specimen alone, the Ackerman grouping was found to be of prognostic value, but apart from nuclear polymorphism the other recorded characteristics (histo-pathological type, histological grading, lymphocyte infiltration, and sinus histiocytosis) did not give any prognostic information. When the axillary node status was included in the multivariate models, the presence of axillary metastases correlated well with the prognosis and the Ackerman classification provided no significant additional information. The results indicate that in cases where the histopathological axillary status is known, little additional prognostic information can be gained from traditional histo-pathological evaluation over and above this status. However, the Ackerman classification and the degree of nuclear polymorphism separate distinct prognostic groups with the same degree of difference in observed survival rates as one discriminated by the axillary node status.

Breast Neoplasms↗
PubMed1987

Activation of mercuric reductase by the substrate NADPH.

Preincubation of the oxidized form of the flavoenzyme mercuric reductase with the reducing substrate, NADPH, or with a high concentration of cysteine (30 mM) results in a substantial increase of the catalytic activity as measured in a standard spectrophotometric assay. Also NADH has some activating effect but NADP+ or EDTA have no effect. In the presence of 1 mM cysteine only one equivalent of NADPH per FAD seems to be required for full activation which occurs after an incubation time of about 10 min. Activated mercuric reductase appears to be stable under anaerobic conditions but eventually returns to the original level of activity in the presence of oxygen. The activated state seems to be stabilized by 1 mM cysteine. Activation of mercuric reductase does not seem to be correlated with a change in the number of reactive thiol groups. The chemical nature of the activation process is not yet understood. Stopped-flow studies have shown that the nonactivated enzyme is practically inactive prior to contact with the substrates. The enzyme is gradually activated during the assay. The kinetics of activation of the 'native' enzyme is biphasic but 'clipped' enzyme, lacking an 85-residue N-terminal domain, is activated in a single first-order process. The progress curves obtained with preactivated enzyme are approximately exponential even at saturating concentrations of NADPH (Km = 0.4 microM at 25 degrees C, pH 7.3) and Hg2+ (Km = 3.2 microM in the presence of 1 mM cysteine). The initial rates yield kcat values of about 13 s-1 per FAD molecule (25 degrees C, pH 7.3). We find no evidence for a thiol-dependent change from a rapid to a slow kinetic phase. The shape of the progress curves presumably depends on product inhibition, but NADP+ is not a sufficiently effective inhibitor to explain the effect fully.

Enzyme Activation↗
PubMed1987

Evaluation of central nervous system involvement in uncomplicated optic neuritis after prolonged follow-up.

Magnetic resonance imaging (MRI), multimodal evoked responses (ER) and HLA antigens were examined in 10 patients with idiopathic acute optic neuritis (ON) without any clinical symptoms or signs of multiple sclerosis (MS) during 9-14 years. In MRI, abnormalities compatible with MS were seen in 4 patients. In spite of clinically unilateral ON, a bilateral abnormality in visual evoked responses (VER) was seen in 3 of 9 cases. Brain stem auditory evoked responses (BAER) were normal in all cases, short latency somatosensory evoked response (SER) in all but one. The cerebrospinal fluid at time of ON showed signs of demyelination in one case only. The frequency of HLA antigens DR2 (78%) and B18 (40%) was significantly increased in comparison to healthy controls. MRI seems to be the most sensitive method in the detection of cerebral lesions of MS, especially in mild or asymptomatic forms of the disease. The present techniques are, however, mostly unable to demonstrate optic nerve lesions which more reliably can be evaluated by VERs. The question whether idiopathic ON represents a form of MS solely, cannot be resolved.

Adult↗