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Biomedical subjects

S Bergström

Publications and source records attributed to S Bergström.

At least 73 records · Page 4Linked to original sources
PubMed1998

The spirochete Borrelia crocidurae causes erythrocyte rosetting during relapsing fever.

Several species of the genus Borrelia exhibit antigenic variation of variable major proteins on their surface during relapsing fever. We have investigated the African relapsing fever species Borrelia crocidurae during infections in mice and compared it with the thoroughly studied North American species Borrelia hermsii. A major difference between the two species is that B. crocidurae can bind and become completely covered with erythrocytes. In addition, B. crocidurae causes a prolonged spirochetemia which coincides with a delayed appearance of antiborrelial antibodies. We show that the antibody response against an unrelated antigen is not delayed and that antibiotic treatment, which dissociates rosettes and inhibits the spirochetes, also leads to an early antibody response. Taken together, the erythrocyte aggregation and prolonged spirochetemia hint at a new mode of immune evasion where erythrocyte-covered spirochetes may avoid contact with the phagocytic cells and B cells of the immune system, thereby delaying the onset of a specific immune response.

Animals↗
PubMed1998

A surface-exposed region of a novel outer membrane protein (P66) of Borrelia spp. is variable in size and sequence.

A model of the 66-kDa outer membrane protein (P66) of Lyme disease Borrelia spp. predicts a surface-exposed loop near the C terminus. This region contains an antigen commonly recognized by sera from Lyme disease patients. In the present study, this region of P66 and homologous proteins of other Borrelia spp. were further investigated by using monoclonal antibodies, epitope mapping of P66 of Borrelia burgdorferi, and DNA sequencing. A monoclonal antibody specific for B. burgdorferi bound to the portion of P66 that was accessible to proteolysis in situ. The linear epitope for the antibody was mapped within a variable segment of the surface-exposed region. To further study this protein, the complete gene of Borrelia hermsii for a protein homologous to P66 was cloned. The deduced protein was 589 amino acids in length and 58% identical to P66 of B. burgdorferi. The B. hermsii P66 protein was predicted to have a surface-exposed region in the same location as that of B. burgdorferi's P66 protein. With primers designed on the basis of conserved sequences and PCR, we identified and cloned the same regions of P66 proteins of Borrelia turicatae, Borrelia parkeri, Borrelia coriaceae, and Borrelia anserina. The deduced protein sequences from all species demonstrated two conserved hydrophobic regions flanking a surface-exposed loop. The loop sequences were highly variable between different Borrelia spp. in both sequence and size, varying between 35 and 45 amino acids. Although the actual function of P66 of Borrelia spp. is unknown, the results suggest that its surface-exposed region is subject to selective pressure.

Amino Acid Sequence↗
PubMed1998

Genital infections among antenatal care attendees in Cape Verde.

In a cross-sectional study, 350 pregnant Capeverdian women were examined to assess the prevalence of Chlamydia trachomatis infection (CT), Neisseria gonorrhoeae infection (NG) and Bacterial vaginosis (BV). Among various analytic methods used, the polymerase chain reaction PCR (for NG, CT) yielded a higher detection rate than did direct microscopy or culture (NG), or direct immuno-fluorescence (CT). Since the PCR analytic of air-dried specimens is not hampered by harsh storage and transport conditions, it could serve to validate other detection methods where laboratory facilities are suboptimal. Among sociodemographic risk factors young age, and currently living alone, were significantly associated with infection.

Adult↗
PubMed1998

Risk factors for perinatal death in Cape Verde.

Risk factors for perinatal death in the Cape Verde islands were assessed among 104 bereaved mothers and 292 mothers of surviving infants in an area-based case-control study in 1992-93. Prospectively gathered information on risk factors was obtained from medical records supplemented with post-partum interviews and anthropometric measurements of mothers and infants. No autopsies were performed. Multiple logistic regression analysis was applied. Out of 23 alleged maternal and two alleged infant risk factors, the following seven proved significantly and independently correlated with perinatal death: first pregnancy (odds ratio [OR] = 2.9); previous hypertensive disease (OR = 4.2); previous perinatal death (OR = 4.6); pre-eclampsia (OR = 7.0); non-cephalic fetal presentation (OR = 17.1); male infant (OR = 2.1) and maternal post-partum fever (OR = 3.1). The perinatal mortality rate was calculated as 37-46/1000 total births. A reduction in the mortality rate warrants antenatal and obstetric care with emphasis on primiparous women; improved detection and treatment of hypertensive disorders and genital infections; and improved intrapartum fetal observation and resuscitation routines.

Adolescent↗
PubMed1998

Vitamin D deficiency in pregnancy is not associated with obstructed labor. A study among Pakistani women in Karachi.

BACKGROUND: Vitamin D deficiency is widespread among pregnant Pakistanis in Norway. It may cause osteomalacia with destruction of maternal pelvis, and thus be a risk factor for cephalopelvic disproportion. This study was performed to determine whether vitamin D deficiency is common among pregnant Pakistanis in Pakistan, and to test the hypothesis that vitamin D deficiency in nulliparous pregnant women is associated with mechanical dystocia. METHODS: The study was carried out at the Civil Hospital, in a poor area of Karachi, and had a case-referent design. Thirty-seven nulliparous parturients with Cesarean section due to mechanical dystocia served as cases, and 80 nulliparous parturients with uncomplicated vaginal delivery were their referents. All blood samples were drawn before parturition. RESULTS: The mothers with obstructed labor were shorter (on average 150 vs. 155 cm, p= 0.0001) and lighter (on average 58 vs. 60.5 kg, p=0.005) than their referents. Seventy-one percent (83/117) of all the participants had marginal or low vitamin D status defined as serum level of calcidiol (25-OH vitamin D3) below 30 nmol/l. Vitamin D deficiency was, however, not more widespread among the mothers with obstructed labor (20/37 vs. 63/80). Furthermore, there were no significant differences in the serum levels of the carboxyterminal telopeptide of type I collagen, a sensitive biochemical marker of bone resorption, (7.2 vs. 6.6 microg/l), and bone specific alkaline phosphate (18.1 vs. 22.0 U/l) a sensitive marker of bone formation. CONCLUSIONS: Vitamin D deficiency in pregnancy is common in Karachi, but is not associated with mechanical dystocia.

Adult↗
PubMed1998

IgG subclasses in Lyme borreliosis: a study of specific IgG subclass distribution in an interferon-gamma-predominated disease.

Lyme borreliosis has shown a T helper type 1 (Th1)-like immune response with high production of interferon-gamma. Since the cytokine environment seems to be important in the regulation of immunoglobulin production and in the switch between different isotypes and subclasses, and since the subclasses of IgG have different functions, we wanted to examine the IgG subclass distribution in Lyme borreliosis. We have developed an ELISA measuring flagellin-specific antibodies of the different IgG subclasses in serum and cerebrospinal fluid (CSF). Thirty-five seropositive patients with varying manifestations of Lyme borreliosis were included in the study. According to the results, the predominating subclasses in both serum and CSF were IgG1 and IgG3. In samples taken early in disease this pattern was more pronounced in patients with a subacute disease, defined as recovery within 3 months, compared to patients that later on developed chronic borreliosis. The levels of IgG2 were generally low and IgG4 was below detection level. Thus, in the IFN-gamma-predominated immune response seen in Lyme borreliosis, mainly IgG1 and IgG3 were found, i.e. the subclasses that are complement activating as well as opsonizing in humans. Increased levels of these two subclasses early in disease might contribute to recovery and counteract the development of chronicity. The absence of IgG4 is in accordance with the presumed Th1-like situation of Lyme borreliosis.

Adult↗
PubMed1998

Is maternal malnutrition associated with a low sex ratio at birth?

The low male/female ratio at birth in African populations has been attributed to a variety of genetic, behavioral, and environmental factors. A low sex ratio at birth has been associated with maternal malnutrition in mammals, but this issue has not been studied in humans. In this study we analyzed the relation between maternal nutritional status and sex ratio at birth in 3282 children born to 684 women from a rural African society. Short maternal stature and obesity were independently related to a low sex ratio at birth. These results are consistent with animal experiments that indicate an adverse effect of maternal malnutrition on male fetuses. The results warrant further research in this area.

Adolescent↗
PubMed1997

[Symphysiotomy. A thought-provoking example of appropriate technique in the Third World].

Cutting through the symphysis pubis cartilage as a means of widening the birth canal during long, drawn-out deliveries was probably common in Europe at the turn of the century and presumably occurred even later. As a result of progress in hygiene and clinical practice, Caesarean section has become much more common in such situations. In developing countries, where supervision of pregnant women is non-existent or extremely poor, Caesarean section can be a dangerous operation. Mortality figures around 1-3% are common, and the women are left with the unfavourable prognosis of a uterine scar. Therefore, symphysiotomy is still practised in settings where neither hygiene nor material resources permit. Caesarean section, because it is simple to perform and makes a negligible demand on resources.

Contraindications↗
PubMed1997

Compartmentalization of antigen specific cytokine responses to the central nervous system in CNS borreliosis: secretion of IFN-gamma predominates over IL-4 secretion in response to outer surface proteins of Lyme disease Borrelia spirochetes.

The neurological manifestations of Lyme disease have been proposed to be partly due to cytokine-mediated immunopathological mechanisms. In this study, the number of Borrelia-specific cells secreting interferon-gamma and interleukin-4 was determined in blood and cerebrospinal fluid from patients with CNS borreliosis (n = 23), other neurological diseases (n = 20), and in blood from healthy controls (n = 10), utilizing an ELISPOT-assay. Elevated specific secretion of IFN-gamma was found in CNS borreliosis, most pronounced in cerebrospinal fluid, whereas secretion of IL-4 was strikingly low. This may indicate that symptoms are due to side effects of the immune response, since IFN-gamma secretion in the absence of corresponding levels of IL-4 may be associated with tissue destruction.

Adult↗
PubMed1997

Reproductive characteristics and post-abortion health consequences in women undergoing illegal and legal abortion in Maputo.

In the Maputo Central Hospital 103 women undergoing induced legal abortion (LA), 103 women with confirmed, recent illegal abortion (IA), and 100 randomly recruited antenatal clinic (AC) attenders were compared in order to find characteristic features regarding obstetric history, reproductive performance and contraceptive knowledge, attitude and practice. Women with IA were younger, had almost never undergone LA, had more often their first sexual intercourse and their first pregnancy below 20 years of age, had less knowledge of contraceptives and more often had never used contraceptives, had fewer previous spontaneous abortions and fewer previous stillbirths than LA women. There were three maternal deaths, all in the IA group. The most frequent illegal abortionist was a health worker (38%). It is concluded that, in this first comparative African study on IA and LA regarding reproductive profile and post-abortion health consequences, the former are at a disadvantage regarding early unprotected sexual intercourse with first pregnancy at a young age and with almost no experience of safe, legal abortion.

Abortion, Illegal↗
PubMed1997

Maternal nutrition and socio-economic status as determinants of birthweight in chronically malnourished African women.

The birthweight is the most important determinant of mortality and morbidity in the neonatal period and may have an influence on health in adult life. The high rate of low birthweight in developing countries is therefore a major health problem. Maternal malnutrition is usually assumed to be a causal factor but other environmental factors are also involved. In this study we analysed maternal nutritional and socio-economic factors as determinants of birthweight in term infants from a rural African society characterised by a high rate of chronic malnutrition. Relations of maternal weight, gestational weight gain, parity, socio-economic status and infant sex with birthweight were analysed in 1,477 women and child pairs. The selected women were followed from early pregnancy and had an uncomplicated delivery at term of a living singleton child. The gestational weight gain was 5.6 (SD 6.0) kg and the mean birthweight 2.933 kg (SD 408). Maternal weight, representing the maternal long-term nutritional situation, was the most important independent determinant of birthweight, accounting for 13.0% of the variance in birthweight. The weight gain, representing the short-term nutritional situation, explained only 5.6% of the variance. Birthweight increased by 20 g (CI 18-23) for each kg maternal weight and by 15 g (CI 12-18) for each kg gestational weight gained. The socio-economic difference in birth-weight was 153 g (CI 109-196) 88 of which (CI 48-128) remained unexplained after adjustment for differences in maternal weight, parity and gender. Improved long-term nutritional situation and living conditions seems to be the most important prerequisites to counteract low birthweight in developing countries.

Birth Weight↗
PubMed1997

A case control study of chorioamniotic infection and histological chorioamnionitis in stillbirth.

In order to elucidate the role and aetiology of chorioamnionitis in stillbirth a case referent study was carried out in 58 pregnant women with late foetal death (cases) and in 58 pregnant women at term with live foetus (referents) matched for age and parity in Maputo Mozambique. Samples from women, stillborns and liveborns, were collected for microbiological and histological assessment. Histological chorioamnionitis was diagnosed in 96% of the cases and in 67% of the referents (OR = 13.5; 95% CI: 2.9-123.9). Escherichia coli was the species most frequently isolated in stillborns; in 14/16 (88%) cases it was isolated from intracardiac fluid. E. coli was associated with chorioamnionitis in 28% of the stillborns as compared to 5% of the referents (OR = 6.9; 95% CI: 1.4-65.4). No group B streptococci were recovered from any placenta or newborn. Vasculitis was present in 12 (21%) cases and in 3 (5%) referents (OR = 4.8; 95%, CI: 1.2-27.7). Histological chorioamnionitis was thus associated with stillbirth. E. coli was common in stillborns. The presence of vasculitis in one fifth of the stillborns indicated that the foetus was alive at the onset of infection.

Age Factors↗
PubMed1997

Immunologic and genetic analyses of VmpA of a neurotropic strain of Borrelia turicatae.

In mice infected with serotype A but not serotype B of the relapsing fever spirochete Borrelia turicatae, early invasion of the brain occurs. Serotypes A and B are further distinguished by the abundant surface protein they produce: VmpA and VmpB, respectively. Western blotting with monoclonal antibodies, one-dimensional peptide mapping, and partial amino acid sequencing demonstrated regions of the VmpA protein that differed from VmpB. Oligonucleotide primers based on the partial amino acid sequences of unique regions were used to amplify a portion of the VmpA gene (vmpA) by PCR, and the product was used as a probe in Southern blot and Northern blot analyses. These experiments showed that (i) expression of the vmpA sequence was determined at the level of transcription and (ii) the vmpA sequence was in two locations in serotype A and one location in serotype B. The vmpA gene at the expression-linked locus of serotype A was cloned and sequenced. An open reading frame would encode a polypeptide of 214 amino acids. The polypeptide expressed by Escherichia coli was bound by VmA-specific but not VmpB-specific antibody. Primer extension analysis identified a consensus sigma70-type promoter for vmpA at the expression locus. Phylogenetic analysis revealed that VmpA is homologous to small Vmp (Vsp) proteins of B. hermsii and to OspC proteins of B. burgdorferi. These findings indicate that a function of the Vsp-OspC family of proteins of Borrelia spp. may be differential localization in organs, including the brain, during infection.

Amino Acid Sequence↗
PubMed1997

The Oms66 (p66) protein is a Borrelia burgdorferi porin.

In this study we report the purification and characterization of a 66-kDa protein, designated Oms66, for outer membrane-spanning 66-kDa protein, that functions as a porin in the outer membrane (OM) of Borrelia burgdorferi. Oms66 was purified by fast-performance liquid chromatography and exhibited an average single-channel conductance of 9.62 +/- 0.37 nS in 1 M KCl, as evidenced by 581 individual insertional events in planar lipid bilayers. Electrophysiological characterization indicated that Oms66 was virtually nonselective between cations and anions and exhibited voltage-dependent closure with multiple substates. The amino acid sequence of tryptic peptides derived from purified Oms66 was identical to the deduced amino acid sequence of p66, a previously described surface-exposed protein of B. burgdorferi. Purified Oms66 was recognized by antiserum specific for p66 and serum from rabbits immune to challenge with virulent B. burgdorferi, indicating that p66 and Oms66 were identical proteins and that Oms66/p66 is an immunogenic protein in infected rabbits. In a methodology that reduces liposomal trapping and nonspecific interactions, native Oms66 was incorporated into liposomes, confirming that Oms66 is an outer membrane-spanning protein. Proteoliposomes containing Oms66 exhibited porin activity nearly identical to that of native, purified Oms66, indicating that reconstituted Oms66 retained native conformation. The use of proteoliposomes reconstituted with Oms66 and other Oms proteins provides an experimental system for determinating the relationship between conformation, protection, and biological function of these molecules.

Amino Acid Sequence↗
PubMed1997

Three variants of parathyroid hormone-related protein messenger RNA are expressed in human mammary gland.

PTH-related protein (PTHrP) is found in a variety of tissues; particularly high levels are present in human milk. The structure of the human PTHrP gene is complex, and alternative splicing allows expression of three different variants PTHrP139, PTHrP173, and PTHrP141, respectively. To determine which of the variants are expressed in human mammary gland a reverse transcriptase polymerase chain reaction (RT-PCR) method was elaborated, distinguishing the three variants. mRNA isolated from human milk cells, human mammary epithelial cells (HMEC) and human nonlactating mammary gland cells were analyzed. The RT-PCR experiments resulted in amplification of DNA fragments corresponding to all three variants for all three cell sources tested. The nucleotide sequences of the PCR fragments were determined and verified to be identical to the reported sequences. Hence, it is concluded that human mammary gland epithelial cells express three variants of PTHrP. Whether these have different physiologic effects in the mammary gland or in the breast fed infant remain to be explored.

Adult↗
PubMed1997

Enteropathogenic bacteria in migrating birds arriving in Sweden.

Birds have been thought to play a role in transmitting infectious agents like influenza, Borrelia and Salmonella. To investigate the role of migrating birds in the dispersal of enteropathogenic bacteria, stool samples from 151 wild birds (50 gulls and 101 passerines) just entering Sweden from their winter grounds were analysed for Salmonella spp., Campylobacter spp. and EHEC O157:H7. The thermophilic isolated enteropathogens found were further analysed by antibiograms. Among the 50 gulls examined, we found 2 isolates of Salmonella typhimurium with multiple antibiotic resistance. Three isolates of C. jejuni were found in the 101 stool samples from passerines. We did not isolate EHEC O157:H7 in any of the bird stools examined.

Animals↗