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Biomedical subjects

L Baumann

Publications and source records attributed to L Baumann.

At least 19 recordsLinked to original sources
PubMed2007

Skin ageing and its treatment.

The effects of chronic sun exposure on skin are readily apparent when skin not typically exposed to the sun and skin regularly exposed to the sun are compared. While the sun is not the only aetiological factor in the dynamic process of skin ageing, it is the primary exogenous cause among several internal and environmental elements. Thus, photo-ageing, the main focus of this article, is a subset of extrinsic skin ageing. The influence of the sun in extrinsic skin ageing, as well as its role in potentially altering the normal course of intrinsic (also known as natural or cellular) ageing, is discussed. Telomeres, the specialized structures found at the ends of chromosomes, are believed to be integral to cellular ageing as well as in the development of cancer. The ageing process, both intrinsic and extrinsic, is also believed to be influenced by the formation of free radicals, also known as reactive oxygen species. The loss of collagen is considered the characteristic histological finding in aged skin. Wrinkling and pigmentary changes are directly associated with photo-ageing and are considered its most salient cutaneous manifestations. Such photodamage represents the cutaneous signs of premature ageing. In addition, deleterious consequences of chronic sun exposure, specifically various forms of photo-induced skin cancer, are also linked to acute and chronic sun exposure. The only known strategies aimed at preventing photo-ageing include sun avoidance, using sunscreens to block or reduce skin exposure to UV radiation, using retinoids to inhibit collagenase synthesis and to promote collagen production, and using anti-oxidants, particularly in combination, to reduce and neutralize free radicals.

Antioxidants↗
PubMed2001

Degenerative minimalism in the genome of a psyllid endosymbiont.

Psyllids, like aphids, feed on plant phloem sap and are obligately associated with prokaryotic endosymbionts acquired through vertical transmission from an ancestral infection. We have sequenced 37 kb of DNA of the genome of Carsonella ruddii, the endosymbiont of psyllids, and found that it has a number of unusual properties revealing a more extreme case of degeneration than was previously reported from studies of eubacterial genomes, including that of the aphid endosymbiont Buchnera aphidicola. Among the unusual properties are an exceptionally low guanine-plus-cytosine content (19.9%), almost complete absence of intergenic spaces, operon fusion, and lack of the usual promoter sequences upstream of 16S rDNA. These features suggest the synthesis of long mRNAs and translational coupling. The most extreme instances of base compositional bias occur in the genes encoding proteins that have less highly conserved amino acid sequences; the guanine-plus-cytosine content of some protein-coding sequences is as low as 10%. The shift in base composition has a large effect on proteins: in polypeptides of C. ruddii, half of the residues consist of five amino acids with codons low in guanine plus cytosine. Furthermore, the proteins of C. ruddii are reduced in size, with an average of about 9% fewer amino acids than in homologous proteins of related bacteria. These observations suggest that the C. ruddii genome is not subject to constraints that limit the evolution of other known eubacteria.

Amino Acids↗
PubMed2000

Secondary endosymbionts of psyllids have been acquired multiple times.

Previous studies have established that psyllids (Hemiptera, Psylloidea) contain primary endosymbionts, designated as Carsonella ruddii, which cospeciate with the psyllid host. This association appears to be the consequence of a single infection of a psyllid ancestor with a bacterium. Some psyllids may have additional secondary (S-) endosymbionts. We have cloned and sequenced the 16S-23S ribosomal RNA genes of seven representative psyllid S-endosymbionts. Comparison of the S-endosymbiont phylogenetic trees with those of C. ruddii indicates a lack of congruence, a finding consistent with multiple infections of psyllids with different precursors of the S-endosymbionts and/or possible horizontal transmission. Additional comparisons indicate that the S-endosymbionts are related to members of the Enterobacteriaceae as well as to several other endosymbionts and insect-associated bacteria.

Animals↗
PubMed2000

Reduced risk of hay fever and asthma among children of farmers.

BACKGROUND: The prevalence of atopic diseases is on the rise. Traditional lifestyles may be associated with a reduced risk of atopy. OBJECTIVES: To test the hypothesis that children living on a farm have lower prevalences of atopic diseases. To identify differences in living conditions between farmers and other families which are associated with the development of atopic conditions. DESIGN: Cross-sectional survey among children entering school (aged 5-7 years). A written questionnaire including the ISAAC core questions and asking for exposures on a farm and elsewhere was administered to the parents. SETTING: School health entry examination in two Bavarian districts with extensive farming activity. SUBJECTS: 10 163 children. MAIN OUTCOME MEASURES: The prevalence of doctor's diagnoses and symptoms of hay fever, asthma and eczema as assessed by parental report. RESULTS: Farmers' children had lower prevalences of hay fever (adjusted odds ratio = 0. 52, 95% CI 0.28-0.99), asthma (0.65, 0.39-1.09), and wheeze (0.55, 0. 36-0.86) than their peers not living in an agricultural environment. The reduction in risk was stronger for children whose families were running the farm on a full-time basis as compared with families with part-time farming activity. Among farmers' children increasing exposure to livestock was related to a decreasing prevalence of atopic diseases (aOR = 0.41, 95% CI 0.23-0.74). CONCLUSIONS: Factors related to environmental influences on a farm such as increased exposure to bacterial compounds in stables where livestock is kept prevent the development of allergic disorders in children.

Agriculture↗
PubMed1999

Genetic characterization of plasmids containing genes encoding enzymes of leucine biosynthesis in endosymbionts (Buchnera) of aphids.

The prokaryotic endosymbionts (Buchnera) of aphids are known to provision their hosts with amino acids that are limiting in the aphid diet. Buchnera from the aphids Schizaphis graminum and Diuraphis noxia have plasmids containing leuABCD, genes that encode enzymes of the leucine biosynthetic pathway, as well as genes encoding proteins probably involved in plasmid replication (repA1 and repA2) and an open reading frame (ORF1) of unknown function. The newly reported plasmids closely resemble a plasmid previously described in Buchnera of the aphid Rhopalosiphum padi [Bracho AM, Martínez-Torres D, Moya A, Latorre A (1995) J Mol Evol 41:67-73]. Nucleotide sequence comparisons indicate conserved regions which may correspond to an origin of replication and two promoters, as well as inverted repeats, one of which resembles a rho-independent terminator. Phylogenetic analyses based on amino acid sequences of leu gene products and ORF1 resulted in trees identical to those obtained from endosymbiont chromosomal genes and the plasmid-borne trpEG. These results are consistent with a single evolutionary origin of the leuABCD-containing plasmid in a common ancestor of Aphididae and the lack of plasmid exchange between endosymbionts of different aphid species. Trees for ORF1 and repA (based on both nucleotides and amino acids) are used to examine the basis for leu plasmid differences between Buchnera of Thelaxes suberi and Aphididae. The most plausible explanation is that a single transfer of the leu genes to an ancestral replicon was followed by rearrangements. The related replicon in Buchnera of Pemphigidae, which lacks leuABCD, appears to represent the ancestral condition, implying that the plasmid location of the leu genes arose after the Pemphigidae diverged from other aphid families. This conclusion parallels previously published observations for the unrelated trpEG plasmid, which is present in Aphididae and absent in Pemphigidae. Recruitment of amino acid biosynthetic genes to plasmids has been ongoing in Buchnera lineages after the infection of aphid hosts.

Animals↗
PubMed1999

Detection of messenger RNA transcribed from genes encoding enzymes of amino acid biosynthesis in Buchnera aphidicola (endosymbiont of aphids).

The aphid Schizaphis graminum is dependent on Buchnera aphidicola, a prokaryotic endosymbiont. One of the functions of the endosymbiont is the synthesis of essential amino acids for the aphid host. Previously we have found that B. aphidicola has many of the genes that encode enzymes of amino acid biosynthesis. Using reverse transcriptase and the polymerase chain reaction, we have detected messenger RNA corresponding to genes involved in the synthesis of tryptophan, isoleucine, valine, leucine, and histidine.

Amino Acids, Essential↗
PubMed1998

Sequence analysis of a 34.7-kb DNA segment from the genome of Buchnera aphidicola (endosymbiont of aphids) containing groEL, dnaA, the atp operon, gidA, and rho.

Buchnera aphidicola is a prokaryotic endosymbiont of the aphid Schizaphis graminum. From past and present nucleotide sequence analyses of the B. aphidicola genome, we have assembled a 34. 7-kilobase (kb) DNA segment. This segment contains genes coding for 32 open reading frames (ORFs), which corresponded to 89.9% of the DNA. All of these ORFs could be identified with homologous regions of the Escherichia coli genome. The order of the genes with established functions was groELS-trmE-rnpA-rpmH-dnaA-dnaN-gyrB-atpCDGAH FEB-gidA-fdx-hscA- hscB-nifS-ilvDC-rep-trxA-rho. The order of genes in small DNA fragments was conserved in both B. aphidicola and E. coli. Most of these fragments were in approximately the same region of the E. coli genome. The latter organism, however, contained many additional inserted genes within and between the fragments. The results of the B. aphidicola genome analyses indicate that the endosymbiont has many properties of free-living bacteria.

Algal Proteins↗
PubMed1998

Characterization of ftsZ, the cell division gene of Buchnera aphidicola (endosymbiont of aphids) and detection of the product.

Buchnera aphidicola, the endosymbiont of the aphid Schizaphis graminum, contains the gene ftsZ, which codes for a protein involved in the initiation of septum formation during cell division. With immunological techniques, this protein has been detected in cell-free extracts of the endosymbiont. Nucleotide sequence determination of a 6.4-kilobase B. aphidicola DNA fragment has indicated that, as in E. coli, ftsZ is adjacent to genes coding for other cell division proteins as well as genes involved in murein synthesis (murC-ddlB-ftsA-ftsZ). Although B. aphidicola ftsZ is expressed in E. coli, it cannot complement E. coli ftsZ mutants. High levels of B. aphidicola FtsZ results in the formation of long filamentous E. coli cells, suggesting that this protein interferes with cell division. The presence of FtsZ indicates that in this, as well as in many other previously described properties, B. aphidicola resembles free-living bacteria.

Amino Acid Sequence↗
PubMed1998

Endosymbionts (Buchnera) from the aphids Schizaphis graminum and Diuraphis noxia have different copy numbers of the plasmid containing the leucine biosynthetic genes.

The prokaryotic endosymbiont (Buchnera) of the aphid Schizaphis graminum contains 24 copies of a plasmid that has genes encoding enzymes of the leucine biosynthetic pathway while the endosymbiont of the related aphid Diuraphis noxia has only one copy of this plasmid. These results, in conjunction with similar results for the trpEG-containing plasmids, suggest that D. noxia has a reduced demand for endosymbiont-derived essential amino acids.

Animals↗
PubMed1998

The endosymbiont (Buchnera) of the aphid Diuraphis noxia contains all the genes of the tryptophan biosynthetic pathway.

Previously it has been shown that the prokaryotic endosymbiont (Buchnera) of the aphid Diuraphis noxia contains a plasmid consisting of one copy of the gene for anthranilate synthase (trpEG) and seven trpEG pseudogenes. In the present communication we show that this endosymbiont contains the remaining genes of the tryptophan biosynthetic pathway [trpDC(F)BA] which appear to be functional in that they code for the complete enzyme proteins and are not pseudogenes. As in the case of Buchnera from other endosymbionts, these genes appear to be organized as one transcription unit and are located on the endosymbiont chromosome.

Animals↗
PubMed1998

Buchnera aphidicola (Aphid endosymbiont) contains genes encoding enzymes of histidine biosynthesis.

Buchnera aphidicola is an endosymbiont of aphids. One of its functions appears to be the synthesis of essential amino acids for the aphid host. A 12.8-kilobase B. aphidicola DNA fragment has been cloned and sequenced. It contains genes encoding all of the enzymes required for the biosynthesis of the essential amino acid histidine. The order of the genes, hisGDCBHAFI, is the same as that found in Escherichia coli and is consistent with their constituting a single transcription unit. The DNA fragment also contained genes involved in aromatic amino acid biosynthesis (aroC), the oxidative pentose pathway (gnd), and 2'-deoxyribonucleotide metabolism (dcd), as well as a tRNA synthase (metG).

Animals↗
PubMed1998

Absence of phospholipase A2 activity in genital Mycoplasma hominis.

The clinical relevance of vaginal colonization with Mycoplasma hominis (M hominis) as a cause of prematurity is doubtful. One of the possible pathways which could explain the role of M hominis in the induction of preterm labour is an increased synthesis of prostaglandins by a phospholipase A2 activity. The aim of this study was to prove whether M hominis secrets proteins with a PLA2 activity and to test whether there are strain differences in the enzyme activity between M hominis isolated from women with normal pregnancy and those with preterm labour. Using specific radio-immunoassay we could not measure any PLA2 activity in the supernatant of all investigated M hominis strains. We exclude the mechanism of induction of preterm labour by M hominis via an increased prostaglandin synthesis. Our findings make a relation between vaginal colonization with M hominis and prematurity unlikely.

Female↗
PubMed1997

Evolution of the tryptophan biosynthetic pathway in Buchnera (aphid endosymbionts): studies of plasmid-associated trpEG within the genus Uroleucon.

Aphids obtain tryptophan from prokaryotic endosymbionts assigned to the genus Buchnera. The rate-limiting enzyme in tryptophan biosynthes, anthranilate synthase, is encoded by the genes trpE and trpG. In Buchnera within the family Aphididae, trpEG is plasmid-borne, apparently as an adaptation to overproduce tryptophan for hosts. To explore the evolution of these plasmids, sequences for trpEG, the upstream region containing the plasmid origin of replication, and chromosomal trpB were obtained for Buchnera of three species in the aphid genus Uroleucon and analyzed together with sequences for six other aphid species. Phylogenies based on trpB and trpEG agree with each other and with previous views of aphid phylogeny. Synonymous substitutions are about twice as high for plasmid-borne genes as for chromosomal genes in the same lineages, suggesting higher mutation rates for genes on plasmids. Nonsynonymous rates for trpEG are accelerated within Buchnera of Uroleucon, indicating a change in selection intensity within this genus. Accelerated evolution within Uroleucon also seems to characterize the upstream region containing the putative origin of replication.

Animals↗
PubMed1997

Buchnera aphidicola (endosymbiont of aphids) contains nuoC(D) genes that encode subunits of NADH dehydrogenase.

A two-kilobase DNA fragment from Buchnera aphidicola, the endosymbiont of aphids, was cloned and sequenced. One open reading frame was detected, coding for a putative protein of 600 amino acids. The N-terminal portion of this protein corresponded to NuoC, while the C-terminal portion corresponded to NuoD. These proteins are constituents of the membrane-associated NADH dehydrogenase. Our results suggest that these two proteins are fused in Buchnera aphidicola, a result consistent with their previously postulated spatial association.

Amino Acid Sequence↗
PubMed1996

The tryptophan biosynthetic pathway of aphid endosymbionts (Buchnera): genetics and evolution of plasmid-associated anthranilate synthase (trpEG) within the aphididae.

The bacterial endosymbionts (Buchnera) from the aphids Rhopalosiphum padi, R. maidis, Schizaphis graminum, and Acyrthosiphon pisum contain the genes for anthranilate synthase (trpEG) on plasmids made up of one or more 3.6-kb units. Anthranilate synthase is the first as well as the rate-limiting enzyme in the tryptophan biosynthetic pathway. The amplification of trpEG on plasmids may result in an increase of enzyme protein and overproduction of this essential amino acid, which is required by the aphid host. The nucleotide sequence of trpEG from endosymbionts of different species of aphids is highly conserved, as is an approximately 500-bp upstream DNA segment which has the characteristics of an origin of replication. Phylogenetic analyses were performed using trpE and trpG from the endosymbionts of these four aphids as well as from the endosymbiont of Schlechtendalia chinensis, in which trpEG occurs on the chromosome. The resulting phylogeny was congruent with trees derived from sequences of two chromosome-located bacterial genes (part of trpB and 16S ribosomal DNA). In turn, trees obtained from plasmid-borne and bacterial chromosome-borne sequences were congruent with the tree resulting from phylogenetic analysis of three aphid mitochondrial regions (portions of the small and large ribosomal DNA subunits, as well as cytochrome oxidase II). Congruence of trees based on genes from host mitochondria and from bacteria adds to previous support for exclusively vertical transmission of the endosymbionts within aphid lineages. Congruence with trees based on plasmid-borne genes supports the origin of the plasmid-borne trpEG from the chromosomal genes of the same lineage and the absence of subsequent plasmid exchange among endosymbionts of different species of aphids.

Amino Acid Sequence↗
PubMed1996

Ribosomal protein S1 (RpsA) of Buchnera aphidicola, the endosymbiont of aphids: characterization of the gene and detection of the product.

Buchnera aphidicola is a prokaryotic endosymbiont found in specialized cells of the aphid Schizaphis graminum. Many of the previously cloned B. aphidicola genes are preceded by a poor ribosome-binding site. Ribosomal protein S1 (RpsA) allows the translation of messenger RNAs that lack or have a poor ribosome binding site. We have cloned and sequenced a 4.5-kilobase (kb) B. aphidicola DNA fragment containing four open reading frames corresponding to aroA-rpsA-himD-tpiA. The deduced amino acid sequence of B. aphidicola RpsA was 75% identical to that of the Escherichia coli protein. The major difference was in the number of basic amino acids, which were present in higher numbers in B. aphidicola RpsA. Antiserum to E. coli RpsA was prepared and used to detect B. aphidicola RpsA in cell-free extracts of aphids. During the first 12 days of aphid growth there is a slight decrease in the amount of RpsA per unit of aphid weight. The three additional genes found on the 4.5-kb DNA fragment encoded for proteins involved in aromatic amino acid biosynthesis (aroA), DNA bending (himD), and carbohydrate metabolism (tpiA). The presence of these genes in B. aphidicola is additional evidence of its similarity to free-living bacteria.

Amino Acid Sequence↗
PubMed1996

Linear atrophoderma of Moulin: a disease which follows Blaschko's lines.

Linear atrophoderma of Moulin is a distinctive disease pattern characterized by hyperpigmented atrophoderma and described originally in 1992. It follows the lines of Blaschko, and occurs without preceding inflammation, subsequent induration or scleroderma. The lesions usually develop during childhood or adolescence, and the prognosis is good. The differential diagnoses include linear dermatoses, e.g. linear scleroderma, epidermal naevi, inflammatory linear verrucous epidermal naevus, lichen striatus, Blaschkitis acuta, reticulate hyperpigmentation of Iijima and linear lupus erythematosus. Diagnosis is made clinically and histologically. We report a 22-year-old woman with a 17 year history of linear atrophoderma which involved the right arm and trunk.

Adult↗