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  • Articles  (9,156)
  • American Chemical Society  (6,780)
  • Blackwell Publishing Ltd  (2,376)
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  • 1980-1984  (2,379)
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  • Medicine  (9,156)
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  • Articles  (9,156)
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  • 1
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The aim of this study was to determine immunogenetic markers of susceptibility in Crohn's disease (CD), taking the different features of the clinical course of the disease into account. HLA class I, HLA class II and TAP transporter gene polymorphisms were studied using DNA typing methods. Gene and antigen frequencies were analysed and compared in a group of 102 CD patients and 200 unrelated healthy controls from the same area. Analysis of the whole CD patient population revealed no definite association with either HLA or TAP gene alleles, with the exception of an association with DRB1*1302 (Pc 〈 0.05). However, when clinical subgroups of patients were considered, specific associations with some genetic markers were found. The most definitive results involved a genetic association in the group of patients who did not respond to glucocorticoid therapy. This group was characterized by a high frequency of HLA-DRB1*04 (P 〈 0.05). Conversely, a positive association with the TAP2-A allele was found in cortico-responder patients (Pc 〈 0.03). Furthermore, analysis of the distribution of HLA class II alleles in relation to the presence of extra-intestinal manifestations revealed an association with the DQB 1*0501 or *0503 suballele of DQ5 (P 〈 0.05). Finally, patients with lesions in the small bowel were more frequently HLA DRB1 *07 (P 〈 0.05). The present study supports the concept of clinical heterogeneity in Crohn's disease associated with a background of genetic heterogeneity.
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  • 2
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    Oxford, UK : Blackwell Publishing Ltd
    International journal of immunogenetics 23 (1996), S. 0 
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Serological HLA types (A, B, C, DR and DQ loci) were studied in five different Indian tribes (Cubeo, Tucano, Coreguaje, Embera and Noanama) belonging to two distinct linguistic families. For all the MHC loci, the range of variation among the five tribes was enormous. Two tribes, Cubeo and Tucano, showed a wide spectrum of antigenic specificities which seemed to be due to admixture from non-tribal groups, while in the other three tribes the polymorphisms of various HLA loci showed restricted distributions. The gene frequency data, when converted to a kinship matrix and a two-dimensional eigenvector plot, indicated that members of the same linguistic family tend to have greater genetic affinity.
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  • 3
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    Oxford, UK : Blackwell Publishing Ltd
    International journal of immunogenetics 23 (1996), S. 0 
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We describe a method for rapid matching of HLA-A, -B and -C allotypes using simultaneous polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and heteroduplex analysis. Electrophoresis is performed at ambient temperature without requirements for buffer cooling. SSCP and heteroduplexes are revealed as discrete spatially separated band clusters. Using HLA-A, -B and -C locus-specific PCR primers, matching for alleles at these loci can be performed in 5h. We tested 17 serologically matched patient-unrelated donor pairs and found considerable microheterogeneity at the DNA level. We propose that this technology has several advantages over conventional low-resolution typing methods and represents a potentially valuable screening method in unrelated donor selection.
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  • 4
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    Oxford, UK : Blackwell Publishing Ltd
    International journal of immunogenetics 23 (1996), S. 0 
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
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  • 5
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    Oxford, UK : Blackwell Publishing Ltd
    International journal of immunogenetics 23 (1996), S. 0 
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
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  • 6
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    Oxford, UK : Blackwell Publishing Ltd
    International journal of immunogenetics 22 (1995), S. 0 
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Investigation of pairs of unrelated persons mismatched for a particular HLA-DQB1 or -DPB1 gene on the induction of cytotoxic T lymphocytes (CTL) revealed that HLA-DQ and HLA-DP antigens provided a slight proliferative stimulus which was, however, sufficient for the generation of CTL. Monomorphic anti-DQ and anti-DP monoclonal antibodies abrogated the induction of cytotoxic response. The results indicate that the HLA-DQ and HLA-DP antigens play a similar role to HLA-DR specificities in clinical bone marrow transplantation.
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  • 7
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    Oxford, UK : Blackwell Publishing Ltd
    International journal of immunogenetics 22 (1995), S. 0 
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
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  • 8
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A negative association between insulin-dependent diabetes mellitus (IDDM) and HLA-DR, DQA1 or DQB1 was found in a large population-based investigation of childhood-onset patients (more than 420 patients) and controls (more than 340 controls) from Sweden. The relative risk was decreased for several haplotypes that were negatively associated with IDDM: DR15-DQA1*0102-DQB1*0602, DR7-DQA1*0201-DQB1*0303, DR14-DQA1*0101-DQB1*0503, DRI1-DQAI*0501-DQB1*0301, DR13-DQA1*0103-DQB1*0603 and DR4-DQA1*0301-DQB1*0301. In a relative predispositional effect (RPE) analysis, however, only the DR15-DQA1*0102-DQB1*0602 haplotype was significantly decreased, which suggests that the major protective effect for IDDM is carried by this haplotype. This was supported by the observation that all genotypes which were negatively associated with IDDM, except DR7/13, included at least one allele from the DR15-DQA1*0102-DQB1*0602 haplotype. Relative predispositional effect (RPE) analysis of genotypes showed further that the DR15-DQA1*0102-DQB1*0602 haplotype was also negatively associated with IDDM when combined with any other haplotype, whether negatively or positively associated with IDDM. This supports previous suggestions that DR15-DQA1*0102-DQB1*0602 acts dominantly. However, both the stratification and the predispositional allele test failed to distinguish the negative association between IDDM and DR15 from that of DQBT0602. On the other hand, these tests indicated that DQA1*0102 was not likely to explain the negative association between IDDM and the DR15-DQA1*0102-DQB1*0602 haplotype. We conclude that the
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  • 9
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    Oxford, UK : Blackwell Publishing Ltd
    International journal of immunogenetics 22 (1995), S. 0 
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A reliable method for high-resolution HLA-DRB1 typing using the combination of group-specific amplification and RFLP analysis is described. Group-specific PCR amplification (multiplex ARMS-PCR) was carried out under the same conditions for all groups using seven different primer pairs divided into four groups: (1) DR1 and DR10; (2) DR2, DR7 and DR9; (3) DR3, DR5, DR6 and DR8, and (4) DR4. The subsequent polyacrylamide gel electrophoresis was used to determine the group(s) contained in each sample. DR1, DR2/7, DR3/5/6/8, DR4, DRB1*0901 and DRB1 * 1001 could be distinguished easily using this system. Computer analysis of the various restriction enzyme cleavage sites was carried out on 105 DRB1 allele sequences. It was shown that all DRB1 alleles, except for five allele pairs and some alleles possessing silent mutations, could be distinguished with commonly available restriction endonucleases. Computer analyses on the discrimination of the heterozygous and homozygous combinations were also carried out. Although some heterozygous combinations could not be distinguished with single digestion, double digestion using two restriction enzymes could distinguish most of such heterozygotes. The results of the typing of 100 Japanese individuals using this method showed good agreement with those obtained by other methods.
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  • 10
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    Oxford, UK : Blackwell Publishing Ltd
    International journal of immunogenetics 22 (1995), S. 0 
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: IgA deficiency (IgA-D) represents the most common immunodeficiency syndrome of infancy. In most cases IgA-D represents an isolated immunological disorder, while sometimes it is associated with IgG subclass deficiency or with the presence of autoantibodies. We investigated the pattern of association of IgA-D with DRB1 and DQB1 loci of the HLA region by DNA molecular typing, which allows the identification of previously serologically undefined specificities. We also compared the gene frequency of DRB1 and DQB1 allelic variants between IgA-D subjects with or without serum autoantibodies. Our results indicate that the gene frequency of the DRB1*0102 subtype and of the DRBP0102, DQB1*0501 haplotype is significantly higher in IgA-D than in the general population. Furthermore, the IgA-D subjects with autoantibodies showed a positive association with DR4 and DR13 subtypes, thus supporting the hypothesis that genetic factors are also involved in the association between IgA-D and autoantibodies.
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  • 11
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    Oxford, UK : Blackwell Publishing Ltd
    International journal of immunogenetics 22 (1995), S. 0 
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Fifteen samples of non-tumoural breast tissue, 24 cases of benign lesions, four biopsies of inflammatory carcinomas and 94 tumour samples of primitive mammary carcinomas were analysed for HLA class II expression. We found, first, that HLA class II antigens were detectable in all cases of non-neoplastic breast tissue. Secondly, HLA class II antigen expression was notably increased in benign neoplasms and hyperplastic lesions. In contrast, only 32 out of 94 carcinomas showed expression of HLA-DR antigens, 17 tumours had HLA-DP antigens and 11 carcinomas were positive for the presence of DQ molecules. The expression of class II antigen was associated with the degree of histological differentiation (P 〈 0.05) but was independent of stromal leucocytic infiltration. Thirdly, HLA-DR was very strongly expressed in intravascular tumoural thrombi, especially in the ‘inflammatory carcinomas’. The immunephenotype of inflammatory infiltrate was analysed in benign and malignant lesions. In malignant lesions the mean number of inflammatory cells was significantly higher than in benign lesions. Interestingly, we found no differences in the amount and composition of inflammatory infiltrate between HLA-DR positive and negative tumours.
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  • 12
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
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  • 13
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    International journal of immunogenetics 22 (1995), S. 0 
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
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  • 14
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Nineteen horse MHC class I specificities have been serologically identified previously at a single locus (ELA-A), and two other specificities appear to be coded at other loci. Biochemical studies indicate that there are at least two expressed loci. In order to establish the number of transcribed horse MHC class I genes, we made a cDNA library from a heterozygous animal (ELA-A3/A7), and screened for positive clones using a bovine class I probe. More than 200 class I clones were isolated in this way, and so far seven unique full length sequences have been identified. All of the sequences are predicted to code for surface expressed, functional molecules. The number of different sequences identified demonstrate that at least four genes are transcribed, although variations in transmembrane length (which is generally conserved in class I loci) suggest that five genes could be represented. Evolutionary analysis of these sequences (and two additional sequences known to represent different horse class I loci) reveals no firm relationships, such that the division between the different loci cannot be discerned. These results suggest an unusual evolutionary history for the horse MHC, the precise nature of which may be revealed only following further cross-species comparisons.
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  • 15
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    Oxford, UK : Blackwell Publishing Ltd
    International journal of immunogenetics 22 (1995), S. 0 
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
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  • 16
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    International journal of immunogenetics 22 (1995), S. 0 
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We studied the allelic constitution at the HLA class II DQA1, DQB1, DRB1 and DPB1 in 94 Italian multiple sclerosis (MS) patients and 98 controls. No significant increase in the frequency of DR2 alleles was detected among MS patients, as previously observed both in European and some Italian studies. A slight increase was found for the DQA 1*0301 and DQB 1*0602 alleles in the MS patients. No significant association was found with the glutamine residue at position 34 of the DQ α chain, which was noted previously in MS patients from northern Europe.
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  • 17
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Fifty-two British and 29 Greek idiopathic membranous nephropathy (IMN) patients were analysed for DRB, DQA1, DQB1 and DPB1 gene polymorphism using second exon amplification and sequence-specific oligonucleotides (SSO). In addition 100 British and 92 Greek controls were analysed.A highly significant increased frequency of the DRB 1*0301 allele was found in IMN patients from Britain (80%), when compared to controls (27%, OR 10.6, P= 0.000004). A lower frequency of DRB 1 *0301 was observed in Greek IMN patients (33%), but this was just significant before correction, when compared to Greek controls (15%, OR 3, P= 0.02). The DRB3 allele most often associated with DRB 1 *0301 was DRB3*0101 (OR 4.2, P= 0.00025) in British patients and DRB3*0201/2 (OR 11, P=0.006) in Greek patients. In Greek IMN patients a decrease in DR16 was found (OR 0.08, P=0.004), and the overall incidence of DR2 was significantly lowered when both sets of IMN patients were combined (OR 0.21, χ2 17.6, P= 0.00013).The incidence of DQA1 *0501 was raised in both Greek (96%vs. 66%, OR 9.7, χ2 6.9, P= 0.009) and British IMN (85%vs. 45%, OR 7.4, χ2 20, P= 0.00007) patients. This gives some support to a proposal for a major role for this allele in IMN. However, DQB1 *0201 was also raised in both Greek (50%vs. 21%, OR 3.6, χ2 8.1, P= 0.005) and British (90%vs. 44%, OR 10, χ2 21.7, P=0.00004) IMN patients. The DQA1*0102 allele was significantly lowered in Greek IMN patients (15%vs. 32%, OR 0.05, 12.2, P=0.0008), probably reflecting a lowering in the DR16 haplotype. No significant difference was observed in the frequencies of DPB alleles in patients and controls.It is concluded that DRB 1*0301 has the strongest association with British Caucasoid IMN. The Greek Caucasoid IMN association with DRB 1*0301 is weaker, and a role for other alleles has not been eliminated.
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  • 18
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    International journal of immunogenetics 22 (1995), S. 0 
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: HLA polymorphisms of class I and class II MHC were investigated in 40 Kuwaiti vitiligo patients and in 40 controls using microcytotoxicity assay. HLA-B21, Cw6 and DR53 were increased significantly in patients compared to controls (P= 0.00001, 0.00001 and P= 0.0053 respectively) while HLA-A19, DR52, were significantly decreased (P= 0.00236,0.05, respectively). Total T-cells, T4 and T8 were measured as CD2, CD4 and CD8 respectively by flow cytometry. Vitiligo patients showed significant increase in CD4 compared to controls (P= 0.03). Our findings suggest that HLA-B21 and Cw6 and DR53, are susceptible genes of vitiligo, while A19 and DR52 are protective genes in the Kuwaiti population.
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  • 19
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    Oxford, UK : Blackwell Publishing Ltd
    International journal of immunogenetics 22 (1995), S. 0 
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We propose to use the extreme diversity of HLA in order to detect, by anonymous check, double registration on computer files, of patients waiting for organ transplantation. A simulation on a panel of 69461 unrelated individuals, caucasoid, confirms the relevance of the method.
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  • 20
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Five human teratoma cell lines have been characterized for the presence of a certain number of marker antigens whose presence or absence has been shown to be characteristic of mouse embryonal carcinoma (EC) cells. Four out of the five lines have been shown to respond to at least some of the criteria associated with murine EC cells even though only limited in vitro differentiation could be demonstrated. The significance of certain unusual marker antigen combinations present on the cell line Tera I and its clones and so far unobserved for the murine model is discussed. The observation in Tera I populations of cells carrying simultaneously both the F9 and β2-microglobulin or HLA antigens, suggest that the human cell lines may represent a novel material for the study of mammalian differentiation.
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  • 21
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    Oxford, UK : Blackwell Publishing Ltd
    International journal of immunogenetics 8 (1981), S. 0 
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Principles of Gene Manipulation. Studies in Microbiology
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  • 22
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    International journal of immunogenetics 7 (1980), S. 0 
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A healthy 22-year-old woman was noted to have erythrocytes of the Pk phenotype: a strong Pk antigen, no detectable P antigen and anti-P antibody in her serum. Her erythrocytes contained four to six times as much Pk glycolipid (globotriaosylceramide or CTH) and approximately half as much P glycolipid (globotertraosylceramide or globoside) as normal red cells. The structures of CTH and globoside were characterized by analysis of permethylated sugars and complement fixation in addition to chromaographic mobility and sugar composition. Inasmuch as the erythrocytes of two Pk individuals that were analysed previously (Marcus et al., 1976) contained no detectable globoside, these abnormalities appear o represent a new phenotype in the P blood group system.
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  • 23
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    International journal of immunogenetics 7 (1980), S. 0 
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We studied 201 unrelated French Basque individuals for HLA and Bf polymorphisms. The haplotypes of eighty-seven of them were deduced from family studies. The results show the frequency of the Bf F1 allele (0.1393) which is the highest one currently reported. They confirm the high frequencies of HLA-Aw19.2 and B18 previously reported in that population and show that a whole haplotype with strong linkage disequilibria, namely Aw19.2, Cw5, B18, Bf F1, DRw3 is frequent. On the other hand, the gene frequency of Bf S is decreased (0.5497) as compared with the other European Caucasoïd populations, while a slight increase in the Bf F gene frequency (0.2960) appears. These results point out that it is of importance to consider the genetic background in choosing the population where linkage disequilibria are to be studied.
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  • 24
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    International journal of immunogenetics 7 (1980), S. 0 
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The genetic control of hybrid resistance to BALB/c fibrosarcoma Meth-A was investigated. A Meth-A tumour grew slower in (BALB/c X C57BL/6)F1 and reciprocal hybrid mice than in syngeneic BALB/c mice and was also found to grow slower in females than in males. Significant F1 resistance was demonstrated after both subcutaneous and intraperitoneal injection of tumour cells. However, (BALB/c X DBA/2)F1 mice did not show any significant resistance to Meth-A. In H-2 linkage studies of [BALB/c X (BALB/c X C57BL/6)] backcross mice, no statistically significant differences in the resistance of H-2 heterozygotes and homozygotes to Meth-A were observed. These results indicated that F1 hybrid resistance to Meth-A was controlled by non-H-2-linked resistance factor(s). No linkage was observed between resistance to Meth-A and coat colour c- and b-loci.
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  • 25
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    International journal of immunogenetics 7 (1980), S. 0 
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: CBA/N mice have an X-linked B cell defect which prevents them from responding to non-mitogenic thymic independent (TI-II) antigens such as dinitrophenylated (DNP-AGG) Ficoll. The F1 male progeny of CBA/N female mice express the same defect. Spleen cell suspensions from such defective mice (CBA/N X C3H/HeN F1 males) could not respond to DNP-AGG-Ficoll following in vitro immunization and subsequent transfer into irradiated, syngeneic, F1 male recipients as expected. In contrast, normal CBA/N X C3H/HeN F1 female spleen cells could respond and effect a ‘rescue'; they mounted strong plaque-foriming cell 7 days after in vitro exposure to DNP-AGG-Ficoll and subsequent transfer into irradiated F1 male recipients. Defective F1 male spleen cells could bind significant quantities of DNP-AGG-Ficoll, however, after, in vitro exposure. Extensive washing of these spleen cells could not reverse this binding. Such DNP-AGG-Ficoll-exposed and washed F1 male spleen cells could, after transfer, aid normal untreated F1 female cells in their rescue function. The defective F1 male spleen cells could convey immunogenic quantities of DNP-AGG-Ficoll to the ‘rescuing’ F1 female cells.Mitomycin treatment of F1 male cells did not interfere with their conveyor function. Goat anti-mouse μ serum impeded the passive antigen conveyor function of defective F1 male cells as did prior exposure to high concentrations of free DNP-AGG hapten. Our data support the view that the B cell defect of CBA/N X C3H/HeN F1 male mice does not relate to antigen binding, but rather to an inability to be effectively triggered by certain cell-bound polymeric antigens.
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  • 26
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    International journal of immunogenetics 7 (1980), S. 0 
    ISSN: 1744-313X
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  • 27
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    International journal of immunogenetics 7 (1980), S. 0 
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Results of a population study with all currently available B-cell specific alloantisera indicate that eight antigens controlled by the RhLA-linked DR locus can now be identified. This leaves a gene frequency of about 0.15 for unidentified or ‘blank’ antigens of that locus. Of the nine identifiable la antigens which are not controlled by the DR locus, three or four may form the basis of a second series which is probably also controlled by the RhLA region.
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  • 28
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    International journal of immunogenetics 7 (1980), S. 0 
    ISSN: 1744-313X
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    Topics: Biology , Medicine
    Notes: Induction of tolerance to bovine serum albumin was studied in mice selected for high (H) or low (L) antibody responsiveness and in their F1 hybrids. No high or low zone tolerances were obtained in H mice whereas L mice were susceptible to tolerance induction by the two schedules. H mice were immunized by repeated injections of tolerogenic BSA for low zone tolerance induction but not after the administration of a single high dose of tolerogenic BSA. Resistance to tolerance induction is dominant in F1 hybrids.
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  • 29
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    International journal of immunogenetics 7 (1980), S. 0 
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: An attempt is made to account for immunoglobulin chain synthesis in terms of genetic events involving IS or controlling elements analogous to those found in bacteria, maize and drosophila. Transposition of variable and constant genes and normal immunoglobulin chain synthesis as well as qualitative and quantitative abnormalities might be explained by such regulatory elements. Intrachromosomal transpositions over short distances would be expressed as apparent hypermutability or redundancy of the variable DNA segment. The constant gene might comprise four sequences coding for the three homology domains and the hinge, separated by intervening sequences. A strong preference for shortrange transposition on the same chromosome and immobilization of the controlling element in the end might account for allelic exclusion.
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  • 30
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    International journal of immunogenetics 7 (1980), S. 0 
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Fab2 fragments from antisera raised in rabbits with partially purified cellular and serum HLA antigens were tested for their ability to block the cytolytic activity of operationally specific HLA-A, B alloantisera. One Fab2 fragment preparation blocked the cytolytic activity of all the HLA-A,B alloantisera tested; the remaining nine inhibited the lytic activity of alloantisera to certain HLA-A,B allospecificities, suggesting that these xenoantisera contain antibody to certain HLA-A,B allotype determinants or to closely associated structures. In contrast to previous reports in the literature none of the xenoantisera contained significant amounts of antibodies to human β2-microglobulin.
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  • 31
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    International journal of immunogenetics 11 (1984), S. 0 
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: NIM-M8 is a monoclonla IgM antibody, specific for the LWab antigen as shown by its reaction with red cells of all donors except those lacking LWa, LWb and LWab. Indirect immunofluorescent staining and cell sorter analyses have shown that LWab is present on a subpopulation of human lymphoctes. Cell fractionation studies indicate that subsets of both B and T cells express LWab and it may, therefore, provide a further marker for heterogeneity in these lymphocyte populations.
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  • 32
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    International journal of immunogenetics 11 (1984), S. 0 
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    Notes: Immunoprecipitation using a monoclonal antibody showed that the Wrb antigen is present on the abnormal (δ-α) hybrid sialoglycoprotein of Sta-positive human erythrocytes but not on the abnormal (δ-α) hybrid sialoglycoprotein of Dantu-positive erythrocytes. These results provide further information regarding the nature and location of the Wrb antigen on the normal erythrocyte sialoglycoprotein α.
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    International journal of immunogenetics 11 (1984), S. 0 
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    Notes: We studied structural and functional characteristics of lymphocytes from adult and fetal baboons (Papio cynocephalus). Flow cytometry with monoclonal antibodies to human lymphocyte antigens and plant lectins was used to define expression of surface antigens on lymphocytes from adult and 140 day fetal baboons (term = 180 days). Major T cell antigenic determinants on adult and fetal baboon lymphocytes were the Tp50, Tp32-45, and p45 glycoproteins detected by monoclonal reagents T11, OKT8, and OKT10 respectively. Baboon T lymphocytes did not react with the OKT3/anti-Leu4 or OKT4/ anti-Leu3a reagents which detect, respectively, Tp19-29 and Tp55, major surface glycoproteins on human T lymphocytes. OKT6, which identifies the human TL antigen equivalent on thymocytes, did not react with baboon thymocytes. These data demonstrate major evolutionary divergence between human and baboon T lymphocytes. By contrast, baboon lymphocytes resembled human peripheral lymphocytes in reactivities with several non-T cell reagents. Lectin binding studies revealed substantially fewer peanut agglutinin-and wheat germ agglutinin-binding cells in suspensions of baboon fetal splenocytes and adult peripheral lymphocytes compared with fetal thymocytes. Thereffore, maturation of baboon T lymphocytes is associated with loss of surface carbohydrate structures that bind these lectins. Adult and fetal baboon lymphocytes resembled human and murine lymphocytes in their capabilities to respond to mitogens and to produce interleukin-2. As in oter species, adult, but not fetal baboon lymphocytes, mediated NK activity against a variety of nucleated target cells. Despite divergence in lymphocyte antigen epression, babbon lymphocyte functional development colsely parallels that seen in humans.
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    International journal of immunogenetics 11 (1984), S. 0 
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    Notes: The Gm, Am and Km immunoglobulin allotypes and ABO blood groups were studied in three groups of Tunisian Berbers.The results showed that the actual Berbers of Tunisia present certain heterogeneity and their ancestors were probably the first inhabitants of North Africa. Indeed, although their Gm-Am haplotypes are mainly Caucasoid, some of them are typically African.The group of Kesra village, the most Caucasoid, shows frequencies of Gm-Am haplotypes very close to those of South European populations, particularly the Spanish, who are probably of the same origin. The gene frequencies of the ABO groups in the three Berber groups were similar to those recorded in European populations with a relatively high frequency of the O genes typical of the Berbers.
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    International journal of immunogenetics 11 (1984), S. 0 
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    Notes: Monoclonal antibody 212.i.4.2 mediated complement-dependent lysis of spleen and lymph node cells carrying the tw1, tw12, tw71, t6, tw73, and tLub1 haplotypes, while cells from mice carrying 11 other t haplotypes were not lysed. The antibody also detected an epitope controlled by genes in the H-2Dd region of non-t mice. A molecule of 46,000 molecular weight was immunoprecipitated by 212.i.4.2 from detergent extracts of 125I-labelled spleen cells of +/tw12 and B10.D2 mice. The H-2dm2 mutation did not alter the expression of the epitope recognized by 212.i.4.2. However, the H-2dm1 mutation decreased the reactivity of lymphoid cells with the antibody in cytotoxicity tests, and 212.i.4.2 immunoprecipitated little or no protein from extracts of B10.D2(R106) spleen cells which carry the H-2dm1 mutation.
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    International journal of immunogenetics 11 (1984), S. 0 
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    Notes: Spleen cells from Balb/c mice given multiple injections of intact human erythrocytes (group O, NN) were fused with NS1 myeloma cells. Culture fluids from the resulting hybrid cells were screened for agglutinating antibody against a panel of erythrocytes. One cell line, 2/23, secreted an IgM antibody which reacted more strongly with NN than with MM cells. Neuraminidase or papain treatment of erythrocytes abolished agglutination whereas trypsin treatment did not. Reactions with U-erythrocytes of different MN phenotypes confirmed the anti-N specificity of monoclonal antibody 2/23. This is the first report of monoclonal anti-N stimulated by the immunization of mice with intact erythrocytes.
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  • 37
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    International journal of immunogenetics 11 (1984), S. 0 
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    Notes: Spleen cells from 30 individual murine irradiation chimeras of the type (P1 x P2)F1→ P1 were compared in a rosetting assay for H-2K and H-2D cell surface antigen expression with normal (P1 x P2)F1 hybrid controls. Eleven out of the 30 chimeras were in the normal range, but the other 19 differed from F1 controls by 4- to 100-fold in endpoint titre for at least one H-2K or H-2D antigen. Every possible class of variation was found, i.e. up or down variation of H-2K or H-2D antigens of P1 or P2 type. This evidence, together with data from T6 chromosome marker experiments which also showed full reconstitution of lethally irradiated P1 recipients by (P1 x P2)F1 donor lymphomyloid stem cells, suggested that incomplete reconstitution was not the cause of H-2 antigenic variation.Low expression of P2 H-2 antigens on spleen cells derived from (P1 x P2)F1→ P1 chimeras was investigated further. Fifteen lethally irradiated (P1 x P2)F1 recipients of bone marrow cells from two such chimeras were all of normal F1 H-2 phenotype when tested 10-12 weeks after reconstitution, thus excluding stable, low P2 H-2-expressing variant F1 stem cells as a cause of the phenomenon. If P1 recipients were hyperimmunized against P2 cells before lethal irradiation and reconstitution with (P1 x P2)F1 stem cells, there were significantly fewer Till-McCulloch colonies in their spleens 10 days after reconstitution than in spleens of unimmunized controls. Also 〉 90% of immunized recients died by 6 weeks after stem cell injection but two survivors both showed very low levels of P2 H-2K and H-2D antigens. These results together with previously published evidence of anti-P2 Tc cell activity and P2 skin graft rejection in (P1 x P2)F1→ P1 chimeras suggested that residual anti-P2 immunological capability in lethally irradiated P1 recipients may be associated with low P2 H-2 expression on their F1-derived spleen cells, although the mechanism does not involve selection of stable, variant F1 stem cells. The mechanism(s) of other classes of variation in H-2 expression in (P1 x P2)F1→ P1 chimeras were not investigated.
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    Notes: RNA was extracted from the splenocytes of Brucella abortus antigen stimulated mice and of control mice. The proportion of chromatographically separated polyadenylated 11.2S mRNA, was determined. With the technique used, only stimulated mice exhibited significant amounts of this RNA species. The highest level was reached 1 day after the stimulation, and the decay from this level presented an oscillatory form during the 4 weeks following the injection.In two different genetic backgrounds, H-2b mice did not respond to the stimulus, in contrast to H-2a and H-2f mice. H-2b/H-2f heterozygotes behaved roughly as intermediate between H-2b and H-2f mice. This genetic control seems to parallel the genetic control of some Brucella-induced, thymus-dependent events previously described.
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    Notes: Book Reviews in this ArticleR. WITKOWSKI and O. PROKOP: Genetik erblicher Syndrome und Mgbildungen. Worterbuch fur die Familienberatung.
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    International journal of immunogenetics 11 (1984), S. 0 
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    Notes: Monoclonal anti-Ia inhibition experiments were conducted to confirm and extend genetic mapping data of I-A gene control of immunity to human haemoglobin (Hb). It was found that the Aβ gene is of critical importance in conferring immunity to the α-chain and β-chain subunits of Hb. A possible involvement of I-E region genes in B10.D2 mice to β-chain is discussed. Through the use of an α-chain specific T cell clone data, is obtained indicating that an intact Ia.8+ Aβ chain is necessary for antigen presentation in vitro.
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  • 41
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    International journal of immunogenetics 10 (1983), S. 0 
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    Notes: C4 is composed of two tightly linked genes (C4A and C4B) lying within the major histocompatibility complex of chromosome 6 that can be demonstrated by agarose gel electrophoresis. Seven alleles and five alleles at the C4A and C4B loci, respectively, were detected in 169 black individuals from the southeastern United States. Furthermore, the phenotypic frequencies of C4A6, C4A5, C4A4, C4B4, C4B3, and C4BQO were significantly different between black and white Americans.
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    International journal of immunogenetics 10 (1983), S. 0 
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    Notes: Two B complex genotypes, B1B1 and B19B19, of outbred line S1, were tested for low and high immune response to GAT, from which four recombinants were recovered: B1B1 GAT-hi and lo, and B19B19 GAT-hi and -lo. Also included in the study were birds of B2B2 genotype with an intermediate level of immune response to GAT.A total of 225 birds of these groups were challenged with the Bryan strain of Rous Sarcoma virus subgroup C, RSV (RAV-7), by inoculation into the wing web at five weeks of age. The B1B1 genotype had the lowest percentage of regressors (17.6%), B19B19 had the highest (42.2%), and the B2B2 genotype was intermediate (23.7%). Combining the results of GAT response over the B1B1 and B19B19 genotypes, 14.0% of GAT-lo and 37.8% of GAT-hi regressed their tumours, respectively. The highly significant (P ≤ 0.01) difference between the combined GAT-hi and -lo groups would suggest that the Rs locus controlling tumour regression induced by the subgroup C virus is closely linked to the region controlling immune response to GAT, but the data also provides evidence that the B-F region of the B complex also plays an important role in RSV-induced tumour regression.
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    Notes: Surface immunoglobulin on spleen cells from NZB and NZB/W mice and congenic mice bearing the nude or X-linked immune defective (Xid) gene was examined by flow microfluorometry with regard to both the frequency of positive cells and density expressed on the cell. These data indicate that although the frequency of unseparated sIg+ B lymphocytes is equivalent among all of these groups of mice, the densities of sIgM and sIgD are different. Spleen cells from these mice were also separated by free-flow electrophoresis and analyzed in a similar manner. This analysis demonstrated the absence of a subpopulation of B lymphocytes with a low electrophoretic mobility and low expression of sIgM. These studies suggest that maturational and/or activation states of the B cells in mice bearing the Xid or nude genes are different from those seen in the parent strains of mice. Such alterations in cell-surface antigens correlate with differences in the natural history of immunopathology of the autoimmune disease in these congenic colonies of New Zealand mice.
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    International journal of immunogenetics 10 (1983), S. 0 
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    Notes: Fifty-five Caucasoid patients with polymalgia rheumatica (PMR) or giant cell arteritis (GCA) were immunoglobulin (Gm) allotyped for this study. Forty-four of these patients had been previously HLA-A,B,C and DR locus allotyped. The incidence of the immunoglobulin allotypic marker Glm(2) was significantly increased in the GCA group (50.00% v. controls 18.75%, P= 〈0.01). There was a similar but insignificant rise of this Gm marker in the PMR group (27.24% v. 18.75%, NS). The increase in Glm(2) in the GCA group was not accompanied by a corresponding rise in the number of people homozygous for Glm(2), i.e., all the increase could be attributed to patients with the Glm(1,2,3): G3m(5,10,21) phenotype.
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    Notes: The strains B 10.S(7R), B 10.S(23 R) and B 10.S(24R), all thought to be genetically identical, differ in levels of susceptibility to infection with Trichinella spiralis. In a series of nine independent experiments, B 10.S(7R) was shown to be more susceptible than the other two strains. In another series of seven experiments, the strain B 10.A(18R) was shown to be more susceptible to infection with T. spiralis than the strains B 10.S(21R) or B 10.BAR-5, all of which were thought to share common H-2 alleles. These results indicate that a gene mapping between the S and D loci influences susceptibility to infection with T. spiralis. Typing of these strains for Qa and Tl loci rule out the possibility of a double crossover accounting for the differences observed. The new gene is designated Ts-2. Previously published data have also been reinterpreted and another gene Ts-1 is shown to be associated with the Aβ locus. When the d allele is expressed at the Ts-2 locus, strains of mice expressing s, q, f or b alleles at Ts-1 are rendered more susceptible to infection.
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    Notes: IgG and IgA heavy chain allotypes were determined in the sera of 483 Caucasian Type 1 diabetes patients and 503 Caucasian healthy controls. There was no significant difference between patients and controls neither on the level of Gm phenotype frequencies nor on the level of Gm three-locus and two-locus haplotype frequencies. A selective IgA deficiency was found in 14 patients (2.9%) but in none of the control individuals (P〈10-4).
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    International journal of immunogenetics 10 (1983), S. 0 
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    Notes: Gm allotypes were detected and quantitated by radioimmunoassay (RIA) in paired serum and CSF samples from patients suffering from various neurological diseases. Of 115 patients with neurological disorders (65 MS and 50 others), seven subjects displayed one or two allotypes in their CSF which were absent in serum. The Gm phenotype in the patient's serum allowed us to infer the genotype without the need of familial data. A comparison of the regression curves obtained in RIA from the unexpected allotype in CSF and the counterpart in a normal serum pool argued for an identity of the Gm antigen carried by both inhibitory molecules. The unexpected allotype(s) in CSF can be considered as the product of a latent Gm gene which may be activated by either immune perturbations due to the disease per se or some particular immune regulations in the central nervous system.
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    Notes: Book reviewed in this article:N. Catsimpoolas; Cell Analysis. Plenum Publishing CorpJ.W.Shay: Techniques In Somatic Cell Genetics
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    Notes: Immunoprecipitaon studies of the rhesus monkey major histocompatibility system have shown that the RhLA-DR locus codes for class II antigens with molecular features that are homologous to the class II antigens coded for by the human HLA-dR locus, The products of another alloantigenic RhLA-linked locus of the rhesus monkey, called ‘48’, is provisionally characterized as a class I system.
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    Notes: The relationships between the antigens recognized by four monoclonal anti-human ‘Ia’-like antibodies were investigated using sequential immunoprecipitation and capping techniques. Two of the antibodies were ‘monomorphic’ and have previously been shown to recognize epitopes in which carbohydrate residues are involved, whereas the two ‘polymorphic’ antibodies recognized protein-defined epitopes—one of these epitopes being present on MB+DR- molecules. In the absence of an indisputable anti-DR monoclonal antibody, it was not possible to conclusively verify which ‘Ia’-encoded antigens were detected by the anti-‘Ia’-like monoclonal antibodies. Nevertheless, several firm conclusions could be drawn: (a) so-called ‘monomorphic’ antibodies do not necessarily react with all ‘Ia’ molecules encoded by a single locus—from the results using the two monomorphic antibodies, B5.1 and 3F1.1, described herein, two populations of antigens being B5.1+3F1.1+ and B5.1+3F1.1- were identified; (b) cross-reactivity of a polymorphic determinant expressed on antigenically-separable ‘Ia’ molecules was noted—using the two polymorphic antibodies, 26.1 and F5C9, molecules which were 26.1+F5C9+ and 26.1-F5C9+ were identified; and (c) the data clearly point to the existence of at least two loci coding for ‘Ia’-like antigens (one of which may or may not be the HLA-DR locus). Given that polymorphisms can now include protein- and carbohydrate-defined epitopes, that cross-reactions occur and that the definition of DR itself by monoclonal antibodies is not clear, the complexity of the human ‘Ia’ antgens is apparent.
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    Notes: We report HLA genotypes in four familial cases of Hodgkin's disease (HD), Nodular Sclerosis (NS) histological subtype, where all patients showed B18 antigen. This finding, although statistically not supported, confirms the possible correlation between HD and B18 antigen which carries a high relative risk in international data.
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    Notes: Previous studies from this laboratory have resulted in the determination of the antigenic structure of sperm-whale myoglobin (Mb). In the present work, we have investigated the fine specificity requirements for T-cell recognition of one of the Mb antigenic sites (antigenic site 5). The antigenic site (peptide 145-153) and seven progressively longer peptides, increasing in length stepwise by two residues at a time, up to 22 residues in length (peptide 132-153), were synthesized. In addition, four truncated peptides were synthesized with intentional deletions at Tyr- 151 and Ala- 144. The T-cell recognition of these purified synthetic peptides was examined here in detail in three strains of mice (BALB/cByJ, B10.D2/n and SJL/J). Mb-primed mice afforded T-cells which proliferated to smaller peptides (two or four residues longer than the site; i.e. peptides 145-153 and 143-153) and more so to the longer peptides 135-153 and 132-153 and to Mb. No response was obtained to the truncated peptides, thus underscoring the fine specificity T-cells. No response was obtained also to intermediate-sized peptides. The latter result, due to an unfavourable mode of folding, suggested a conformational dependency in T-lymphocyte recognition.
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    Notes: Serum blood samples from 563 of the total 700 Nganasans, members of the isolate in the northern-most part of Siberia were tested for G1m, (z,a,x,f), G2m (n), G3m (g,b0,b1,b3,b5,s,t), and km (1) allotypic determinants. Additionally, 78 Yenisey Samoyeds (Entsi) who are the Nganasan's western neighbours were studied. Both populations are remarkable for high frequency of ‘Northern Oriental’Gm (za;.;b0b3b5st) which appears to be the most frequent haplotype in the Nganasans (0.486), and is the second frequent in Yenisey Samoyeds (0.276). The Gm (f;b) generalized haplotype which used to be considered as an indicator of Caucasian gene flow occurred in the Nganasans in the very low frequency of 0.008, versus 0.045 revealed in adjoining Yenisey Samoyeds. Both populations also differ in the frequency of Km1 which is two times lower in the Nganasans (0.048), than in Yenisey Samoyeds (0.103). When segregation ratios for the Gm locus were inspected in 67 Nganasan families, no apparent deviations from Mendelian expectations, and no recombinant phenotypes were observed.
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    Notes: Genetic control of PQ prolongation of the electrocardiogram (ECG) in the mouse, immunized with killed group A streptococci, was studied by using various congenic mice. Mice of H-2a, H-2k and H-2f haplotypes showed high frequencies of PQ prolongation, while haplotypes of H-2b, H-2d and H-2s showed low frequencies of PQ prolongation. Studies using various recombinant mice revealed that at least one immune-associated (Ir) gene mapped in the left side of the I-B subregion. High responsiveness of F1 hybrids of H-2b and H-2d, as well as B1O.A(5R) and B10.A(3R), suggests the existence of a complementing gene. In addition, the differences between C3H and CKB, as well as differences between C3H.SW and CWB, indicate that another Ir gene maps in the immunoglobulin heavy chain (Igh) coding loci. Repeated injections of anti-I-J or anti-I-A antisera also modified this PQ prolongation. These results suggested that both the major histocompatibility complex (MHC) and immunoglobulin (Igh) loci seem to be playing important roles in the pathogenesis of PQ prolongation.
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    Notes: The growth and reproduction complex contains recessive genes (grc) which influence body weight and gonadal development. Homozygous males are sterile, and they have an arrest of spermatogenesis at the primary spermatocyte stage. Homozygous females are fertile but have a reduced reproductive capacity. The data presented in this paper show that the latter defect is associated with a decrease in the relative number of secondary ovarian follicles and an increase in the number of atretic follicles. This finding indicates that most of the primary follicles do not mature properly. Thus, the genetic defect in gametogenesis controlled by the grc appears to occur at the same stage of development in both females and males.
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    Molecular microbiology 28 (1998), S. 0 
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    Notes: Nucleoside diphosphate kinase (Ndk) is an important enzyme that generates nucleoside triphosphates (NTPs) or their deoxy derivatives by terminal phosphotransfer from an NTP such as ATP or GTP to any nucleoside diphosphate or its deoxy derivative. As NTPs, particularly GTP, are important for cellular macromolecular synthesis and signalling mechanisms, Ndk plays an important role in bacterial growth, signal transduction and pathogenicity. Specific examples of the role of Ndk in regulating growth, NTP formation and cell surface polysaccharide synthesis in two respiratory tract pathogens, Pseudomonas aeruginosa and Mycobacterium tuberculosis, are discussed.
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    Molecular microbiology 28 (1998), S. 0 
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    Notes: The BvgAS signal transduction system in Bordetella spp. mediates a transition between infectious (Bvg+) and non-infectious (Bvg−) phases by sensing environmental conditions and regulating gene expression. Using differential display, arbitrary-primed polymerase chain reaction (PCR), we identified a gene expressed in the Bvg+ phase of Bordetella bronchiseptica that shows a high degree of sequence similarity to a locus involved in providing energy for type III secretion in pathogenic Gram-negative bacteria (yscN in Yersinia spp.). We determined that the expression of this homologue in B. bronchiseptica (designated bscN ) is regulated by bvg. Several open reading frames surrounding the bscN locus also show sequence similarity to loci encoding type III secretion apparatus components in other bacteria. An in-frame deletion of bscN in B. bronchiseptica leads to decreased secretion of several proteins, decreased cytotoxicity towards cultured cell lines and a defect in causing tyrosine dephosphorylation of specific proteins in infected cells in vitro. The deletion strain also revealed that bscN-mediated secretion is required for persistent colonization of the trachea in a rat infection model. Loci encoding type III secretion homologues were identified in four strains of B. pertussis and two strains of B. parapertussis. B. pertussis strain 18323 and an ovine isolate of B. parapertussis show significant transcription of the genes in vitro.
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  • 61
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    Notes: The transcription of the osmC gene of Escherichia coli is regulated as a function of the phase of growth. It is induced during the decelerating phase, before entry into stationary phase. osmC expression is directed by two overlapping promoters, osmCp1 and osmCp2. osmCp2 is mainly transcribed by E-σs, the RNA polymerase using the σs (RpoS) sigma factor, and is responsible for the growth phase regulation. Transcription from osmCp1 is independent of σs. The leucine-responsive protein (Lrp) has been shown to bind the osmC promoter region in band shift experiments. In vivo analysis using osmC–lacZ transcriptional fusions demonstrated that Lrp affects the expression of both promoters. It represses the transcription of osmCp1 and activates the transcription of osmCp2 by E-σs. An absence of Lrp results in an increase in the amount of RpoS during exponential growth in minimal medium. The nucleoid-associated protein H-NS also represses osmC transcription from both promoters. However, this happens through different mechanisms. The effect on osmCp2 is probably mediated by the increase in σs concentration in the cytoplasm of hns− mutants, while the effect on osmCp1 is independent of σs. No binding of H-NS to the promoter region DNA could be detected, indicating that the effect on osmCp1 could also be indirect.
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  • 62
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    Molecular microbiology 30 (1998), S. 0 
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    Notes: Expression of the Myxococcus xanthus gene crtI is controlled by a light-inducible promoter. The activity of this promoter depends on CarQ, a σ factor of the extracytoplasmic function (ECF) subfamily. Here, we show that the minimum DNA stretch reproducing normal expression of crtI extends from a few bases upstream of the −35 position to a site well downstream of the transcriptional start. The downstream DNA contains an enhancer-like element that remains active when displaced upstream of the promoter. Experimental evidence is provided for the activity of the crtI promoter being critically dependent on a pentanucleotide sequence centred at the −31 position. The similarity of this sequence with the consensus for ECF-σ-dependent promoters from other bacteria is discussed. The activity of the crtI promoter also depends on certain basepairs at the −10 region. Hence, the operation of ECF-σ-factors seems to require binding to two different DNA sites, although the −10 sequences of different ECF-σ-dependent promoters are unrelated to one another, and the ECF-σ-factors themselves lack the conserved domain known to mediate binding of other σ-factors to the −10 DNA site.
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  • 63
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    Notes: We constructed hybrid proteins containing a plant α-galactosidase fused to various C-terminal moieties of the hypoxic Srp1p; this allowed us to identify a cell wall-bound form of Srp1p. We showed that the last 30 amino acids of Srp1p, but not the last 16, contain sufficient information to signal glycosyl-phosphatidylinositol anchor attachment and subsequent cell wall anchorage. The cell wall-bound form was shown to be linked by means of a β1,6-glucose-containing side-chain. Pmt1p enzyme is known as a protein-O-mannosyltransferase that initiates the O-glycosidic chains on proteins. We found that a pmt1 deletion mutant was highly sensitive to zymolyase and that in this strain the α-galactosidase–Srp1 fusion proteins, an α-galactosidase–Sed1 hybrid protein and an α-galactosidase–α-agglutinin hybrid protein were absent from both the membrane and the cell wall fractions. However, the plasma membrane protein Gas1p still receives its glycosyl-phosphatidylinositol anchor in pmt1 cells, and in this mutant strain an α-galactosidase–Cwp2 fusion protein was found linked to the cell wall but devoid of β1,6-glucan side-chain, indicating an alternative mechanism of cell wall anchorage.
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  • 64
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    Molecular microbiology 27 (1998), S. 0 
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    Notes: We have studied the genomic structure and constructed the SpeI, PacI and I-CeuI restriction maps of the four biovars of the pathogenic bacterium Brucella suis. B. suis biovar 1 has two chromosomes of 2.1 Mb and 1.15 Mb, similar to those of the other Brucella species: B. melitensis, B. abortus, B. ovis and B. neotomae. Two chromosomes were also observed in the genome of B. suis biovars 2 and 4, but with sizes of 1.85 Mb and 1.35 Mb, whereas only one chromosome with a size of 3.1 Mb was found in B. suis biovar 3. We show that the differences in chromosome size and number can be explained by rearrangements at chromosomal regions containing the three rrn genes. The location and orientation of these genes confirmed that these rearrangements are due to homologous recombination at the rrn loci. This observation allows us to propose a scheme for the evolution of the genus Brucella in which the two chromosome-containing strains can emerge from an hypothetical ancestor with a single chromosome, which is probably similar to that of B. suis biovar 3. As the genus Brucella is certainly monospecific, this is the first time that differences in chromosome number have been observed in strains of the same bacterial species.
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  • 65
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    Molecular microbiology 27 (1998), S. 0 
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  • 66
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    Molecular microbiology 27 (1998), S. 0 
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    Notes: Complementation by transformation of an Aspergillus niger mutant lacking xylanolytic activity led to the isolation of the xlnR gene. The xlnR gene encodes a polypeptide of 875 amino acids capable of forming a zinc binuclear cluster domain with similarity to the zinc clusters of the GAL4 superfamily of transcription factors. The XlnR-binding site 5′-GGCTAAA-3′ was deduced after electrophoretic mobility shift assays, DNase I footprinting and comparison of various xylanolytic promoters. The importance of the second G within the presumed XlnR binding site 5′-GGCTAAA-3′ was confirmed in vitro and in vivo. The 5′-GGCTAAA-3′ consensus sequence is found within several xylanolytic promoters of various Aspergillus species and Penicillium chrysogenum. Therefore, this sequence may be an important and conserved cis-acting element in induction of xylanolytic genes in filamentous fungi. Our results indicate that XlnR is a transcriptional activator of the xylanolytic system in A. niger.
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  • 67
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    Notes: Group A colicins need proteins of the Escherichia coli envelope Tol complex (TolA, TolB, TolQ and TolR) to reach their cellular target. The N-terminal domain of colicins is involved in the import process. The N-terminal domains of colicins A and E1 have been shown to interact with TolA, and the N-terminal domain of colicin E3 has been shown to interact with TolB. We found that a pentapeptide conserved in the N-terminal domain of all group A colicins, the ‘TolA box’, was important for colicin A import but was not involved in the colicin A–TolA interaction. It was, however, involved in the colicin A–TolB interaction. The interactions of colicin A N-terminal domain deletion mutants with TolA and TolB were investigated. Random mutagenesis was performed on a construct allowing the colicin A N-terminal domain to be exported in the bacteria periplasm. This enabled us to select mutant protein domains unable to compete with the wild-type domain of the entire colicin A for import into the cells. Our results demonstrate that different regions of the colicin A N-terminal domain interact with TolA and TolB. The colicin A N-terminal domain was also shown to form a trimeric complex with TolA and TolB.
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  • 68
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    Molecular microbiology 27 (1998), S. 0 
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  • 69
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    Molecular microbiology 24 (1997), S. 0 
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    Notes: The energy requirement for the second step in pullulanase secretion by the general secretory pathway was studied in Escherichia coli. In order to uncouple the two steps in the secretion pathway (across the cytoplasmic and outer membranes, respectively) and to facilitate kinetic analysis of secretion, a variant form of pullulanase lacking its N-terminal fatty acid membrane anchor was used. The transport of the periplasmic secretion intermediate form of this protein across the outer membrane was not inhibited by concentrations of sodium arsenate in excess of those required to reduce ATP levels to ≤10% of their normal value. Pullulanase secretion was inhibited by the protonophore carbonyl cyanide m-chlorophenyl hydrazone at concentrations which were similar to those reported by others to be required to prevent solute uptake or the export and processing of preproteins across the cytoplasmic membrane, but which were in excess of those required to fully dissipate the proton-motive force and to reduce lactose uptake to a significant extent.
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  • 70
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    Molecular microbiology 24 (1997), S. 0 
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    Notes: The Yersinia pseudotuberculosis pH 6 antigen mediates haemagglutination and adhesion to cultured mammalian cells. The synthesis of pH 6 antigen requires the products of the psaEFABC genes in both Yersinia pseudotuberculosis and Escherichia coli. In-frame deletion mutations of psaE and psaF caused defective haemagglutination. In contrast, we showed that the psaABC genes were sufficient for haemagglutination if they were expressed by a heterologous promoter. Environmental regulation of pH 6 antigen by temperature and pH occurs via regulation of the major pilus protein PsaA at the transcriptional level. Northern blot analyses indicate that the psaA transcript was absent in either psaE or psaF mutant strains. Primer extension analyses indicate that, in Y. pseudotuberculosis, the transcription of the psaE and psaF genes is constitutive. Alkaline phosphatase fusion studies confirm the topology prediction that PsaE and PsaF are both inner-membrane-associated proteins. PsaE consists of an N-terminal cytoplasmic domain, containing sequence similarity to transcriptional regulators found in two-component systems as well as to the Salmonella typhimurium HilA protein, with a C-terminal domain that is periplasmically localized. PsaF is predicted to be oriented with most of the protein in the periplasm, the hydrophobic N-terminus being either integrated in the inner membrane or cleaved as a signal peptide.
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  • 71
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    Notes: Mycoplasma mycoides contains a signal-recognition particle (SRP) composed of an RNA molecule and an SRP54 homologue (Ffh). We have now identified a mycoplasma homologue to the α subunit of the mammalian SRP receptor and Escherichia coli FtsY. The protein (MmFtsY) was expressed in E. coli and purified to homogeneity. MmFtsY has a weak intrinsic GTPase activity but GTP hydrolysis was markedly stimulated when it was combined with mycoplasma Ffh (MmFfh) and SRP RNA. Also, in the absence of SRP RNA GTPase activity was significantly enhanced. Furthermore, GTP hydrolysis was stimulated when MmFtsY was combined with the N-terminal GTPase domain (N+G) of MmFfh. These findings indicate that basic features of the GTPase activation mechanism are independent of the C-terminal M domain of the MmFfh protein. We propose that the activation is mediated to a large extent by contacts between the GTPase domains of the mycoplasma Ffh and FtsY proteins and that the contribution of the M domain and SRP RNA in the activation mechanism is mainly for modifying the conformation of the MmFfh GTPase domain.
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  • 72
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    Notes: The structural genes for the cyanide-insensitive terminal oxidase (CIO) of Pseudomonas aeruginosa were sequenced. The locus comprised two open reading frames, cioA and cioB, coding for gene products of 488 and 335 amino acid residues with predicted molecular masses of 54 241 and 37 016 Da respectively. These genes were encoded by a 2.7 kb transcript and probably comprise an operon. Upstream of a major transcriptional start site is a −10 promoter region and, approximately at nucleotides −50 and +13, there are sequences homologous to the binding site of the transcriptional regulator Anr. The deduced amino acid sequences of CioA and CioB are homologous to the cytochrome bd quinol oxidases of Escherichia coli and Azotobacter vinelandii. However, no cytochrome d-like signals were found in wild-type P. aeruginosa strains. An atypical cytochrome d-like signal was seen under low-aeration growth conditions but only in strains in which the cioAB genes were present on a high-copy-number plasmid. The appearance of these cytochrome d-like signals was not paralleled by a concomitant increase in CIO activity. These data support the hypothesis that the CIO of P. aeruginosa does not contain haem d. This raises the possibility that there is a family of bacterial quinol oxidases related to the cytochrome bd of E. coli that can differ in their haem composition from the E. coli paradigm.
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  • 73
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    Molecular microbiology 24 (1997), S. 0 
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    Notes: Most small multicopy plasmids of Gram-positive bacteria and many in Gram-negative bacteria replicate by a rolling-circle (RC) mechanism. The replication initiator proteins encoded by the RC plasmids and single-stranded bacteriophages of Escherichia coli have origin-specific nicking-closing activities that are required for the initiation and termination of RC replication. We have investigated the sequence requirements for termination of RC replication of plasmid pT181. The initiator nick site is located in the loop of a hairpin region (IRII) within the pT181 origin of replication. By mutational analysis, we have found that several nucleotides within the stem of IRII which are critical for the initiation activity are dispensable for termination of replication. We also demonstrate that nucleotides in the right arm of IRII, but not the left arm, are absolutely required for termination of RC replication. We have also identified specific nucleotides in IRII that are critical for its termination activity. The sequence of the right arm of the hairpin must be located downstream of the initiator nick site for termination, suggesting that termination requires a specific orientation of the initiator protein at the origin.
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  • 74
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    Molecular microbiology 24 (1997), S. 0 
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    Notes: Bacillus subtilis responds to signals of environmental and metabolic stress by inducing over 40 general stress genes under the control of the σB transcription factor. σB activity is regulated post-translationally by a multicomponent network composed of two coupled partner-switching modules, RsbX-RsbS-RsbT and RsbU-RsbV-RsbW, each containing a serine phosphatase (X or U), an antagonist protein (S or V), and a switch protein/serine kinase (T or W). The upstream module (X-S-T) is required to transmit signals of environmental stress. In contrast, the downstream module (U-V-W) is required to transmit signals of energy stress as well as the environmental signals conveyed to it from the upstream module. Until now the function of the rsbR gene product was unknown. RsbR shares significant sequence similarity with the RsbS and RsbV antagonist proteins whose phosphorylation states control key protein–protein interactions within their respective modules. Here we present evidence that RsbR is associated with RsbS in the upstream, environmental-sensing module. To investigate RsbR function, we constructed deletion and point mutations within rsbR and tested their effects on expression of σB-dependent reporter fusions, both singly and in combination with other rsb mutations. To determine the possible interaction of RsbR with other Rsb proteins, we tested the ability of wild-type or mutant RsbR to activate transcription in the yeast two-hybrid system in conjunction with other Rsb regulators. On the basis of this genetic analysis, we conclude that RsbR is a positive regulator which modulates σB activity in response to salt and heat stress. Our data further suggest that: (i) RsbR influences the antagonist function of RsbS by direct protein–protein interaction; and (ii) this interaction with RsbS is likely controlled by the phosphorylation state of RsbR.
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  • 75
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    Molecular microbiology 24 (1997), S. 0 
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    Notes: Enhancer-dependent transcription in bacteria requires the alternative transcription factor σN (σ54), which forms an RNA polymerase holoenzyme that binds promoters as a transcriptionally inactive complex. We have examined the structure of σN by circular dichroism (CD) analysis. The σN protein and its domains are well structured in the absence of the core RNA polymerase subunits or promoter DNA. Denaturation of σN by temperature as followed by changes in CD shows a concomitant loss of secondary and tertiary structures with a melting temperature of 36°C. The secondary structure displays a two-state melting curve with a second Tm of 85°C. The amino-terminal Region I activation domain together with the acidic Region II does not contribute to the two-state melting. In marked contrast, the integrity of the C-terminal DNA-binding domain is required for the two-state melting. Measurements of pKb also demonstrated that a C-terminal part of σN, but not regions I or I + II, is required for the structural integrity of σN at high pH. Measurements of pKa suggested that α-helical structures are important in σN for the establishment of tertiary structural elements. The tertiary structure near ultraviolet CD signals of σN do not require regions I or I + II but were strongly diminished by C-terminal truncation of σN. Promoter DNA binding resulted in aconformational change in σN, permitting the determination of a binding constant. A typical B-DNA conformation was adopted by the promoter DNA. Implications for the modular domain organization of σN, the function of C-terminal sequences, and domain communication and its role in activation of transcription are discussed.
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  • 76
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    Notes: Expression of the global stress protein gene (gspA) is induced during the intracellular infection of macrophages and upon exposure of Legionella pneumophila to in vitro stress stimuli. Transcription of gspA is regulated by two promoters, one of which is regulated by the σ32 heat-shock transcription factor. We utilized a gspA promoter fusion to a promoterless lacZ to probe the phagososmal ‘microenvironment’ for the kinetics of exposure of intracellular L. pneumophila to stress stimuli. Expression through the gspA promoter was constitutively induced by approx. 16-fold throughout the intracellular infection, and occurred predominantly through the σ32-regulated promoter. Expression of the gspA promoter was induced approx. 4.5-fold, 5-, 11- and 9-fold upon exposure of L. pneumophila to heat shock, oxidative stress, acid shock, and osmotic shock, respectively. An isogenic insertion mutant of L. pneumophila in gspA (strain AA224) was constructed by allelic exchange in the wild-type strain AA200. Compared to in vitro-grown wild-type strain AA200, AA224 was more susceptible to all four in vitro stress stimuli. The wild-type phenotypes were restored to strain AA224 by complementation with a plasmid containing wild-type gspA. There was no difference between the wild-type strain and the gspA mutant in cytopathogenicity to U937 cells or in their kinetics of intracellular replication within macrophages and amoebae. However, compared to in vitro-grown bacteria, macrophage-grown and amoebae-grown AA200 and AA224 showed an equal and dramatic increase in resistance to in vitro stress stimuli. Our data showed that regardless of the capacity of L. pneumophila to subvert the microbicidal mechanisms of the macrophage, intracellular L. pneumophila is exposed to a high level of stress stimuli throughout the intracellular infection. Although the GspA protein is required for protection of the bacteria against in vitro stress stimuli, and is induced during intracellular multiplication, the loss of its function is probably compensated for by other macrophage-induced and stress-induced proteins within the intracellular environment.
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  • 77
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    Molecular microbiology 23 (1997), S. 0 
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    Notes: Lysostaphin is an extracellular glycylglycine endopep-tidase produced by Staphylococcus simulans biovar staphylolyticus ATCC1362 that lyses staphylococcal cells by hydrolysing the polyglycine interpeptide bridges of the peptidoglycan. Renewed analysis of the sequence of the lysostaphin gene (Iss), and the sequencing of the amino-terminus of purified prolysostaphin and of mature lysostaphin revealed that lysostaphin is organized as a preproprotein of 493 amino acids (aa), with a signal peptide consisting of 36 aa, a propeptide of 211 aa from which 195 aa are organized in 15 tandem repeats of 13 aa length, and a mature protein of 246 aa. Prolysostaphin is processed in the culture supernatant of S. simulans biovar staphylolyticus by an extracellular cysteine protease. Although prolysostaphin was staphylolytically active, the mature lysostaphin was about 4.5-fold more active. The controlled expression in Staphylococcus carnosus of Iss and Iss with deletions in the prepropeptide region indicated that the tandem repeats of the propeptide are not necessary for protein export or activation of Lss, but keep Lss in a less active state. Intracellular expressed pro- and mature lysostaphin exert staphy-lolytic activity in cell-free extracts, but do not affect growth of the corresponding clones. We characterized a lysostaphin immunity factor gene (lif) which is located in the opposite direction to Iss. The expression of lif in S. carnosus led to an increase in the serine/glycine ratio of the interpeptide bridges of peptidoglycan from 2 to 35%, suggesting that lysostaphin immunity depends on serine incorporation into the interpeptide bridge. If, in addition to lif, Iss is co-expressed the serine/glycine ratio is further increased to 58%, suggesting that Lss selects for optimal serine incorporation. Lif shows similarity to FemA and FemB
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  • 78
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    Notes: Catabolite repression of Bacillus subtilis catabolic operons is supposed to occur via a negative regulatory mechanism involving the recognition of a cis-acting catabolite-responsive element (cre) by a complex of CcpA, which is a member of the GalR-LacI family of bacterial regulatory proteins, and the seryl-phos-phorylated form of HPr (P-ser-HPr), as verified by recent studies on catabolite repression of the gnt operon. Analysis of the gnt promoter region by deletions and point mutations revealed that in addition to the ere in the first gene (gntR) of the gnt operon (credown), this operon contains another ere located in the promoter region (creup). A translational gntR-lacZ fusion expressed under the control of various combinations of wild-type and mutant credown and creup was integrated into the chromosomal amyE locus, and then catabolite repression of p-galac-tosidase synthesis in the resultant integrants was examined. The in vivo results implied that catabolite repression exerted by creup was probably independent of catabolite repression exerted by credown; both creup and credown catabolite repression involved CcpA. Catabolite repression exerted by creup was independent of P-ser-HPr, and catabolite repression exerted by credown was partially independent of P-ser-HPr. DNase I footprinting experiments indicated that a complex of CcpA and P-ser-HPr did not recognize creup, in contrast to its specific recognition of credown. However, CcpA complexed with glucose-6-phosphate specifically recognized creup as well as credown, but the physiological significance of this complexing is unknown.
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  • 79
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    Molecular microbiology 23 (1997), S. 0 
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    Notes: A transposition mutant of Bacillus subtilis (designated JC901) that was isolated on the basis of growth inhibition by Na at elevated pH, was deficient in energy-dependent Na extrusion. The capacity of the mutant JC901 for Na -dependent pH homeostasis was unaffected relative to the wild-type strain, as assessed by regulation of cytoplasmic pH after an alkaline shift. The site of transposition was near the 3 -terminal end of a gene, natB, predicted to encode a membrane protein, NatB. NatB possesses six putative membrane-spanning regions at its C-terminus, and exhibits modest sequence similarity to regions of eukaryotic Na+/H+ exchangers. Sequence and Northern blot analyses suggested that natB forms an operon with an upstream gene, natA. The predicted product of natA is a member of the family of ATP-binding proteins that are components of transport systems of the ATP-binding cassette (ABC) or traffic ATPase type. Expression of the lacZ gene that was under control of the promoter for natAB indicated that expression of the operon was induced by ethanol and the protonophore carbonylcyanide p-chlorophenylhydrazone (CCCP), and, more modestly, by Na+, and K+, but not by choline or a high concentration of sucrose. Restoration of the natAB genes, cloned in a recombinant plasmid (pJY1), complemented the Na+-sensitive phe-notype of the mutant JC901 at elevated pH and significantly increased the resistance of the mutant to growth inhibition by ethanol and CCCP at pH 7; ethanol was not excluded, however, from the cells expressing natAB, so ethanol-resistance does not result from NatAB-dependent ethanol efflux. Transformation of the mutant with pJY1 did markedly enhance the capacity for Na+
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  • 80
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    Molecular microbiology 23 (1997), S. 0 
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    Notes: The polA gene of Escherichia coli encodes DNA polymerase I that is involved in DNA replication and repair. Despite the wide knowledge about structure and function of DNA polymerase I, there is little insight into the regulatory mechanisms involved in polA expression. DnaA is the initiator protein for DNA replication in E. coli. There are two putative DnaA-binding sites within the extended promoter region of polA. In this work we studied the influence of altered levels of DnaA protein on polA expression. We found that DnaA overproduction increases polA expression in stationary-phase cultures. The stimulation effect was independent of rpoS, which encodes the sigma factor for stationary-phase-inducible genes. However, it was modulated by ppGpp. Comparative S1 analyses revealed that the induction was based on transcriptional stimulation. Footprint-ing experiments demonstrated that DnaA binds only to the proximal DnaA box near the polA promoter. These results suggest an additional role for DnaA as transcriptional activator of polA at least under certain physiological conditions.
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  • 81
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    Notes: Bacillus anthracis, the aetiological agent of anthrax, is a Gram-positive spore-forming bacterium. The cell wall of vegetative cells of B. anthracis is surrounded by an S-layer. An array remained when sap, a gene described as encoding an S-layer component, was deleted. The remaining S-layer component, termed EA1, is chromosomally encoded. The gene encoding EA1 (eag) was obtained on two overlapping fragments in Escherichia coli and shown to be contiguous to the sap gene. The EA1 amino acid sequence, deduced from the eag nucleotide sequence, shows classical S-layer protein features (no cysteine, only 0.1% methionine, 10% lysine, and a weakly acidic pi). Similar to Sap and other Gram-positive surface proteins, EA1 has three 'S-layer-homology’motifs immediately downstream from a signal peptide. Single- and double-disrupted mutants were constructed. EA1 and Sap were co-localized at the cell surface of the wild-type bacilli. However, EA1 was more tightly bound than Sap to the bacteria. Electron microscopy studies and in vivo experiments with the constructed mutants showed that EA1 constitutes the main lattice of the B. anthracis S-layer, and is the major cell-associated antigen.
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    Molecular microbiology 23 (1997), S. 0 
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    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Shuttle mutagenesis has been adapted to randomly mutate the genome of Neisseria gonorrhoeae (gono-coccus; Gc). A size-restricted plasmid library of Gc strain FA1090 was mutated with the mini-transposon mTnEGNS. Randomness was tested by checking for transposon insertion bias between vector and insert DNA, Gc transformation efficiency of individual mutated clones, and representation of unique clones before and after Gc transformation with a mutated pool of DNA. Mutants created by random shuttle mutagenesis were screened, using a colony-based polymerase chain reaction assay, for the ability to undergo pilin antigenic variation. Out of 8064 mutants screened, 22 unique transposon insertion mutants were found to be antigenic variation deficient (Avd). The Avd mutants were separated into five types according to recombination defect-associated phenotypes, including colony growth, natural DNA transformation competence, and repair of DNA damage caused by ultraviolet radiation.
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  • 83
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    Molecular microbiology 23 (1997), S. 0 
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    Topics: Biology , Medicine
    Notes: Minichromosomes are plasmids with the origin of chromosome replication, oriC, as their only origin of replication. In Escherichia coli, minichromosomes are compatible with the chromosome and replicate in a cell-cycle-specific manner at the same time as oriC located on the chromosome initiates replication. In int strains, oriC has been inactivated and replaced by a plasmid origin. Because plasmids control their own replication, chromosome replication is uncoupled from the normal cell-cycle control and is random with respect to the cell cycle in the int strains. We have used an intP1 strain to address the question of whether minicromosome replication is coupled to the replication of the chromosome or is governed by cell-cycle-specific signals. Minichromosome replication was analysed by density-shift experiments and found not to be random in the randomly replicating intP1 host. This suggests that the cell-cycle-specific control functions of oriC replication are operating also in the intP1 strain.
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  • 84
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    Notes: The Tar chemotactic signal transducer of Escherichia coli mediates attractant responses to L-aspartate and to maltose. Aspartate binds across the subunit interface of the periplasmic receptor domain of a Tar homodimer. Maltose, in contrast, first binds to the periplasmic maltose-binding protein (MBP), which in its ligand-stabilized closed form then interacts with Tar. Intragenic complementation was used to determine the MBP-binding site on the Tar dimer. Mutations causing certain substitutions at residues Tyr-143, Asn-145, Gly-147, Tyr-149, and Phe-150 of Tar lead to severe defects in maltose chemotaxis, as do certain mutations affecting residues Arg-73, Met-76, Asp-77, and Ser-83. These two sets of mutations defined two complementation groups when the defective proteins were co-expressed at equal levels from compatible plasmids. We conclude that MBP contacts both subunits of the Tar dimer simultaneously and asymmetrically. Mutations affecting Met-75 could not be complemented, suggesting that this residue is important for association of MBP with each subunit of the Tar dimer. When the residues involved in interaction with MBP were mapped onto the crystal structure of the Tar periplasmic domain, they localized to a groove at the membrane-distal apex of the domain and also extended onto one shoulder of the apical region.
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  • 85
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    Topics: Biology , Medicine
    Notes: In Saccharomyces cerevisiae, two positive transcription factors of the GATA family, Gln3p and NiMp/ Gatlp, upregulate the expression of multiple nitrogen pathway genes via upstream 5-GATA-3′ sequences. Another GATA factor, Uga43p/Da180p, downregulates to varying degrees the expression of some nitrogen-regulated genes. Here, we report the functional analysis of a fourth GATA factor, Gzf 3p/Ni12p, whose gene was discovered by systematic sequencing of chromosome X. The Gzf3 protein most closely resembles Uga43p. Similar to Uga43p, Gzf3p has the properties of a negative GATA factor. While Uga43p is active specifically under nitrogen-derepression conditions, Gzf 3p exerts its negative regulatory function specifically on preferred nitrogen sources: it is involved in nitrogen repression of NiMp-dependent transcription. At least one positive GATA factor is required for the UGA43 and GZF3 genes to be expressed. The Uga43p factor negatively regulates GZF3 expression and vice versa. In addition, both Uga43p and Gzf3p moderately regulate expression of their own genes. These two proteins seem to be parts of a complex network of GATA factors which probably play a determining role in nitrogen-regulated transcription.
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  • 86
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    Molecular microbiology 23 (1997), S. 0 
    ISSN: 1365-2958
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    Topics: Biology , Medicine
    Notes: Formation of araB-lacZ coding-sequence fusions is a key adaptive mutation system. Eighty-four independent araB-lacZ fusions were sequenced. All fusions carried rearranged MuR linker sequences between the araB and lacZ domains indicating that they arose from the standard intermediate of the well-characterized Mu DNA rearrangement process, the strand transfer complex (STC). Five non-standard araB-lacZ fusions isolated after indirect sib selection had novel structures containing back-to-back inverted MuR linkers. The observation that different isolation procedures gave rise to standard and non-standard fusions indicates that cellular physiology can influence late steps in the multi-step biochemical sequence leading to araB-lacZ fusions. Each araB-lacZ fusion contained two novel DNA junctions. The MuR-lacZ junctions showed‘hot-spotting’according to established rules for Mu target selection. The araB-MuR and MuR-MuR junctions all involved exchanges at regions of short sequence homology. More extensive homology between MuR and araB sequences indicates potential STC isomerization into a resolvable four-way structure analogous to a Holliday junction. These results highlight the molecular complexity of araB-lacZ fusion formation, which may be thought of as a multi-step cell biological process rather than a unitary biochemical reaction.
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  • 87
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    Topics: Biology , Medicine
    Notes: Mutations in the seven clustered rpf genes cause downregulated synthesis of extracellular enzymes and reduced virulence of Xanthomonas campestris pathovar campestris (Xcc). The phenotype of mutants in one of the genes, rpfF, can be restored by a diffusible extracellular factor (DSF) produced by all Xcc strains tested, apart from rpfF and rpfB mutants. DSF accumulates in early stationary phase (when synthesis of enzymes is maximal), but levels decline subsequently. Addition of DSF to exponentially-growing wild-type bacteria does not cause precocious enzyme synthesis. rpfB and rpfF are expressed throughout growth, but the rate increases in early stationary phase. RpfB is predicted to be a long-chain fatty acyl CoA ligase, and RpfF shows some relatedness to enoyl CoA hydratases. The properties of DSF suggest that it may be a fatty-acid derivative, and certain lipid preparations possess DSF activity at higher concentrations. These include lipid extracts and acid-hydrolysed lipopolysaccharide and lipid A from Xcc, and purified dodecanoic and hydroxydodecanoic acid. DSF production is confined to certain xanthomonads. We propose a model for the DSF system, which represents a novel mechanism for regulating virulence factor synthesis in response to physiological or environmental changes.
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  • 88
    ISSN: 1365-2958
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    Topics: Biology , Medicine
    Notes: The general amino acid permease, Gap1, of Saccharomyces cerevisiae is very active in cells grown on proline as the sole nitrogen source. Adding NH4+ to the medium triggers inactivation and degradation of the permease via a regulatory process involving Npi1p/Rsp5p, a ubiquitin–protein ligase. In this study, we describe several mutations affecting the C-terminal region of Gap1p that render the permease resistant to NH4+-induced inactivation. An in vivo isolated mutation (gap1pgr ) causes a single Glu→Lys substitution in an amino acid context similar to the DXKSS sequence involved in ubiquitination and endocytosis of the yeast α-factor receptor, Ste2p. Another replacement, substitution of two alanines for a di-leucine motif, likewise protects the Gap1 permease against NH4+-induced inactivation. In mammalian cells, such a motif is involved in the internalization of several cell-surface proteins. These data provide the first indication that a di-leucine motif influences the function of a plasma membrane protein in yeast. Mutagenesis of a putative phosphorylation site upstream from the di-leucine motif altered neither the activity nor the regulation of the permease. In contrast, deletion of the last eleven amino acids of Gap1p, a region conserved in other amino acid permeases, conferred resistance to NH4+ inactivation. Although the C-terminal region of Gap1p plays an important role in nitrogen control of activity, it was not sufficient to confer this regulation to two NH4+-insensitive permeases, namely the arginine (Can1p) and uracil (Fur4p) permeases.
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  • 89
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    Topics: Biology , Medicine
    Notes: The hlyX gene of the pig pathogen Actinobacillus pleuropneumoniae encodes HlyX, a homologue of FNR, the anaerobic transcription regulator of Escherichia coli. The hlyX gene complements the anaerobic respiratory deficiencies of E. coli fnr mutants but also induces the expression of an otherwise latent haemolysin. Therefore, FNR and HlyX have distinct but overlapping regulons. The hlyX gene has been overexpressed as a gst ::hlyX fusion and the HlyX protein purified. Similar to FNR, HlyX can acquire a [4Fe–4S] cluster, which promotes binding to the FNR box (Kd of 20–30 nM) under anaerobic conditions. Expression of hlyX in E. coli induced the anaerobic production of at least five polypeptides, including the yfiD gene product, which were not induced by fnr. Analysis of the yfiD promoter region revealed the presence of two FNR boxes situated at −61.5 and −114.5. Consistent with this observation, expression from the semi-synthetic Class I promoter FF+20pmelR was efficiently activated by HlyX but not by FNR. The weaker level of FNR-mediated activation of Class I promoters suggests that there is a poorer activating contact (activating region 1 (AR1) equivalent) between FNR and RNA polymerase at these promoters and that HlyX possesses an additional or improved AR1. The AR1 of HlyX is partially characterized by a surface-exposed region around amino acid A187, which confers the altered specificity and provides an explanation for the existence of distinct but overlapping HlyX and FNR regulons.
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  • 90
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    Molecular microbiology 22 (1996), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Sulphate transport in Neurospora crassa is achieved by two distinct sulphate permeases, I and II, encoded by the cys-13 and cys-14 genes, respectively. The synthesis of both sulphate permeases is subject to sulphur repression and requires the global positive-acting regulatory protein CYS3. CYS3, a bZIP DNA-binding protein, regulates cys-14 expression at the transcriptional level and binds in vitro specifically to three DNA-recognition sites, A, B, and C, in the cys-14 upstream region. In vivo functional analysis of the cys-14 promoter was carried out with 5’deletions and by deletions or mutations of CYS3 DNA-binding sites. The most distal CYS3-binding site, C, located 1.4kb upstream of the transcriptional start site, is necessary and sufficient to mediate strong transcriptional activation by CYS3; moreover, site C was able to function equally well when it was located at variable distances upstream of the cys-14 gene. Site B, located 1 kb upstream, alone is able to support a moderate degree of cys-14 expression. Site A is not required and does not appear to play any functional role in cys-14 expression, even though it is in close proximity to the transcriptional start site. The presence of multiple copies of CYS3-binding elements A or B in the cys-14 promoter results in a parallel increase of regulated gene expression. When a transforming cys-14 gene becomes integrated at ectopic locations in the host genome, it can be expressed in an unregulated fashion, presumably by coming under the control of other promoter elements. Our results also suggested that at least one enzyme in the sulphate catabolic pathway requires a functional CYS3 protein for expression.
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  • 91
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    Molecular microbiology 22 (1996), S. 0 
    ISSN: 1365-2958
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    Topics: Biology , Medicine
    Notes: Amoebae of Dictyostelium discoideum release ammonia during development, and the accumulation of this weak base is believed to be responsible for inhibiting fruiting-body formation and switching aggregates into migrating slugs. Exposure to weak bases can also inhibit aggregation and cell-type specific gene expression. The pathway by which weak bases influence development is not understood. We show here that the development of a set of mutants defective in acidification of intracellular acidic compartments is abnormally sensitive to inhibition by weak bases. Moreover even in the absence of added weak bases these mutants are delayed in aggregation and have a protracted migratory phase. The same behaviour is observed in trans-formants harbouring an antisense construct for one of the vacuolar H+-ATPase subunits. These results support the idea that weak bases exert their effects by inhibiting acidification of an intracellular acidic compartment.
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  • 92
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    Molecular microbiology 22 (1996), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The alternative sigma factor RpoS (σs) is required for Salmonella virulence in mice. We report the immunizing capacity of Salmonella typhimurlum rpoS and rpoS aroA mutants to protect susceptible BALB/c mice against subsequent oral challenge with virulent S. typhimurium. When administered orally or intraperitoneally, rpoS derivatives of the mouse-virulent S. typhimurium strains, C52 and SL1344, were highly attenuated and were efficient single-dose live vaccines. rpoS aroA mutants were more attenuated than corresponding single aroA or rpoS mutants, as assessed after oral or intraperitoneal administration, but retained significant ability to protect mice against salmonellosis. Salmonella rpoS and rpoS aroA mutants therefore deserve serious consideration for rational vaccine design. Consistent with this, Salmonella typhi Ty2, a ‘wild-type’ strain used widely for the development of human live-vaccine candidates against typhoid fever, was shown to be defective for rpoS. In addition, our results demonstrate that rpoS not only controls the growth and persistence of S. typhimurium in deep lymphoid organs, but also plays a role during the initial stages of oral infection.
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  • 93
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    Topics: Biology , Medicine
    Notes: We have initiated a project to sequence the 3Mbp genome of the thermoacidophilic archaebacterium Sulfolobus solfataricus P2. Cosmids were selected from a provisional set of minimally overlapping clones, subcloned in pUC18, and sequenced using a hybrid (random plus directed) strategy to give two blocks of contiguous unique sequence, respectively, 100389 and 56105bp. These two contigs contain a total of 163 open reading frames (ORFs) in 26–29 putative operons; 56 ORFs could be identified with reasonable certainty. Clusters of ORFs potentially encode proteins of glycogen biosynthesis, oxidative decarboxylation of pyruvate, ATP-dependent transport across membranes, isoprenoid biosynthesis, protein synthesis, and ribosomes. Putative promoters occur upstream of most ORFs. Thirty per cent of the predicted strong and medium-strength promoters can initiate transcription at the start codon or within 10 nucleotides upstream, indicating a process of initial mRNA-ribosome contact unlike that of most eubacterial genes. A novel termination motif is proposed to account for 15 additional terminations. The two contigs differ in densities of ORFs, insertion elements and repeated sequences; together they contain two copies of the previously reported insertion sequence ISC 1217, five additional IS elements representing four novel types, four classes of long non-IS repeated sequences, and numerous short, perfect repeats.
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  • 94
    ISSN: 1365-2958
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    Topics: Biology , Medicine
    Notes: Legionella pneumophila is the causative agent of a severe form of pneumonia in humans (Legionnaires’disease). A major virulence factor, the Mip protein (FK506-binding protein, FKBP25mem), belongs to the enzyme family of peptidyl-prolyl cis/trans isomerases (PPIases). Here we show that L. pneumophila Philadelphia I possesses an additional cytoplasmic PPiase at a level of enzyme activity comparable to that of FKBP25mem. The N-terminal amino acid sequence of the purified protein was obtained by Edman degradation and showed that the protein is a member of the cyclophilin family of PPIases. The Icy gene (Legionella cycophn) was cloned and sequenced. It encodes a putative 164-amino-acid protein with a molecular mass of 17 968 Da called L. pneumophila cyclophilin 18 (L. p. Cyp18). Amino acid sequence comparison displays considerable similarity to the cytoplasmic and the periplasmic cyclophilins of Escherichia coll with 60.5% and 51.5% identity, respectively. The substrate specificity and inhibition by cyclosporin A revealed a pattern that is typically found for other bacterial cyclophilins. An L. pneumophila Cyp18 derivative with a 19-amino-acid polypeptide extension including a 6-histi-dine tag and an enterokinase cleavage site exhibits
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  • 95
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    Molecular microbiology 21 (1996), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Transcription of fimA, the Escherichia coli gene encoding the type 1 fimbrial subunit protein, is driven by a promoter carried on a 314bp segment of invertible DNA. We have discovered that overexpression of fimB, one of the genes required for inversion of this DNA element, results in transcriptional repression of fimA. Furthermore, under these conditions inversion ceases to be dependent on the integration host factor (IHF) or the leucine-responsive regulatory protein (LRP), cofactors hitherto considered to be essential for inversion. Inversion will even occur (albeit at a very low level) in the absence of both cofactors. The interaction of the fimB gene product with the invertible element was studied in vivo in the presence of single- and multicopy fimB genes. Dimethyl sulphoxide (DMS)-mediated methylation of DNA at the 9 bp inverted repeats, which flank the invertible element, was found to vary in the presence and absence of functional fimB. The DMS reactivity profile at the left-hand inverted repeat was similar with single or multicopy fimB. The corresponding profile at the right-hand inverted repeat varied with fimB copy number. As this repeat lies between the fimA promoter and open reading frame, FimB binding here is likely to modulate fimA transcription and vice versa.
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  • 96
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    Molecular microbiology 21 (1996), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The function of the S-layer, a regularly arranged structure on the outside of numerous bacteria, appears to be different for bacteria living in different environments. Almost no similarity exists between the primary sequences of S-proteins, although their amino acid composition is comparable. S-protein production is directed by single or multiple promoters in front of the S-protein gene, yielding stable mRNAs. Most bacteria secrete S-proteins via the general secretory pathway (GSP). Translocation of S-protein across the outer membrane of Gram-negative bacteria sometimes occurs by S-protein-specific branches of the GSP. O-polysaccharide side-chains of the lipopolysaccharide component of the cell wall of Gram-negative bacteria appear to function as receptors for attachment of the S-layer. Silent S-protein genes have been found in Campylobacter fetus and Lactobacillus acidophilus. These silent genes are placed in the expression site in a fraction of the bacterial population via inversion of a chromosomal segment.
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  • 97
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    Molecular microbiology 21 (1996), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The cold-shock response, characterized by a specific pattern of gene expression, is induced upon a downshift in temperature and in the presence of inhibitors of ribosomal function. Here, we demonstrate that RbfA of Escherichia coli, considered to be involved in ribosomal maturation and/or initiation of translation, is a cold-shock protein. Shifting the rbfA mutant to a lower temperature resulted in a constitutive induction of the cold-shock response accompanied by slower growth at low temperatures, while shifting the rbfA mutant that overproduces wild-type RbfA resulted in an increase in total protein synthesis accompanied by faster growth adaptation to the lower temperature. Furthermore, the cold-shock response was also constitutively induced in a cold-sensitive 16S rRNA mutant at low temperatures. Accompanying the transient induction of the cold-shock response, we also report that shifting E. coli from 37°C to 15°C resulted in a temporary inhibition of initiation of translation, as evidenced by the transient decrease in polysomes accompanied by the transient increase in 70S monosomes. The accumulative data indicate that the inducing signal for the cold-shock response is the increase in the level of cold-unadapted non-translatable ribo-somes which are converted to cold-adapted translatable ribosomes by the association of cold-shock proteins such as RbfA. Therefore, the expression of the cold-shock response, and thus cellular adaptation to low temperature, is regulated at the level of translation. The data also indicate that cold-shock proteins can be translated by ribosomes under conditions that are not translatable for most mRNAs.
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  • 98
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    Molecular microbiology 21 (1996), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Chromosomally encoded systems present in a variety of bacteria appear to play a central role in determining the intrinsic level of resistance to many commonly used antibiotics. Work with the Gram-negative bacterium Escherichia coli has shown that there is significant similarity at the amino acid sequence level among the structural components of these resistance systems as well as among their genetic regulators. This review describes two of the better-studied regulatory systems, marRAB and soxRS, as well as two regulated multidrug-efflux systems, encoded by emrAB and acrAB, and focuses on conserved themes in their primary structures and environmental stimuli. The observed resistance to clinically important antibiotics appears to reflect an overlap with broad-ranged adaptive responses by free-living bacteria to noxious plant materials in their natural environment.
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  • 99
    ISSN: 1365-2958
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    Topics: Biology , Medicine
    Notes: Intracellular endosymbiotic bacteria inherent to ants of the genus Camponotus were characterized. The bacteria were localized in bacteriocytes, which are specialized cells of both workers and queen ants; these cells are intercalated between epithelial cells of the midgut. The bacteriocytes show a different morphology from the normal epithelial cells and carry a large number of the rod-shaped Gram-negative bacteria free in the cytoplasm. The bacteria were never observed in the neighbouring epithelial cells, but they were found intracellularly in oocytes, strongly indicating a maternal transmission of the bacteria. The 16S DNA encoding rrs loci of the endosymbionts of four species of the genus Camponotus derived either from Germany (C. herculeanus and C. ligniperdus), North America (C. floridanus) or South America (C. rufipes) were cloned after polymerase chain reaction (PCR) amplification using oligonucleotides complementary to all so far known eubacterial rrs sequences. The DNA sequences of the rrs loci of the four endosymbionts were determined, and, using various genus- and species-specific oligonucleotides derived from variable regions in the rrs sequences, the identity of the bacteria present in the bacteriocytes and the ovarian cells was confirmed by PCR and in situ hybridization techniques. Comparison of the 16S DNA sequences with the available database showed the endosymbiotic bacteria to be members of the γ-subclass of Proteobacteria. They formed a distinct taxonomic group, a sister taxon of the taxons defined by the tsetse fly and aphid endosymbionts. Within the γ-subclass, the cluster of the ant, tsetse fly and aphid endosymbionts are placed adjacent to the family of Enterobacteriaceae. The evolutionary tree of the ant endosymbionts reflects the systematic classification and geographical distribution of their host insects, indicating an early co-evolution of the symbiotic partners and a vertical transmission of the bacteria.
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  • 100
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    Molecular microbiology 21 (1996), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Some strains of enterotoxigenic Escherichia coli associated with human diarrhoeal disease produce a class of pili represented by those called CS1. For the assembly of the major-pilin subunit, CooA, into pili, each of four linked genes, cooB,A,C, and D, is required. In this study, we have determined the subcellular localization of CooB, C and D, and investigated the molecular interactions of these proteins using specific antisera. CooD appears to be an integral pilus protein because it co-purifies with, and is strongly associated with, CS1 pili. In keeping with its role as an assembly protein, the CooD minor pilin (when overexpressed in CS1-piliated strains) was detected in periplasmic inter-molecular complexes with the major-pilin subunit CooA. CooB is an assembly protein found exclusively in the periplasm of CS1-piliated strains. CooB also forms periplasmic intermolecular complexes with CooA, but does not constitute part of the final pilus structure. Immunoblot analysis of cell fractions showed that CooC is an outer membrane protein of CS1-piliated E. coli. Based on this information, we have proposed a model for CS1 -pilus assembly which is very similar to the model for polymerization of the PapA pilin of uropathogenic E. coli. As the assembly proteins of Pap and CS1 pili are structurally unrelated, this may represent a case of convergent evolution.
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