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Biomedical subjects

U Hentschel

Publications and source records attributed to U Hentschel.

At least 19 recordsLinked to original sources
PubMed2003

Microbial diversity of marine sponges.

The recent application of molecular microbial ecology tools to sponge-microbe associations has revealed a glimpse into the biodiversity of these microbial communities, that is considered just 'the tip of the iceberg'. This chapter provides an overview over these new findings with regard to identity, diversity and distribution patterns of sponge-associated microbial consortia. The sponges Aplysina aerophoba (Verongida), Rhopaloeides odorabile (Dicytoceratida) and Theonella swinhoei (Lithistida) were chosen as model systems for this review because they have been subject to both, cultivation-dependent and cultivation-independent approaches. A discussion of the microbial assemblages of Halichondriapanicea is presented in the accompanying chapter by Imhoff and Stöhr. Considering that a large fraction of sponge-associated microbes is not yet amenable to cultivation, an emphasis has been placed on the techniques centering around the 16S rRNA gene. A section has been included that covers the potential of sponge microbial communities for drug discovery. Finally, a 'sponge-microbe interaction model' is presented that summarizes our current understanding of the processes that might have shaped the community structure of the microbial assemblages within sponges.

Animals↗
PubMed2003

Sorbicillactone A: a structurally unprecedented bioactive novel-type alkaloid from a sponge-derived fungus.

This chapter deals with the discovery of sorbicillactone A, as an illustrative example of the fruitful cooperation within BIOTECmarin--its isolation and chemical characterization, and its biological activities. Sorbicillactone A was isolated from a strain of Penicillium chrysogenum cultured from a sample of the Mediterranean sponge Ircinia fasciculata; it possesses a unique bicyclic lactone structure, seemingly derived from sorbicillin. Among the numerous known sorbicillin-derived structures, it is the first found to contain nitrogen and thus the first representative of a novel type of 'sorbicillin alkaloids', apparently originating from a likewise remarkable biosynthesis. Furthermore, the compound exhibits promising activities in several mammalian and viral test systems, in particular a highly selective cytostatic activity against murine leukemic lymphoblasts (L5178y) and the ability to protect human T cells against the cytopathic effects of HIV-1. These properties qualify sorbicillactone A or one of its derivatives for animal and (hopefully) also future therapeutic human trials.

Alkaloids↗
PubMed2001

On the problem of establishing the subcellular localization of Dictyostelium retrotransposon TRE5-A proteins by biochemical analysis of nuclear extracts.

At first sight a protein that is enriched in extracts prepared from nuclei by means of biochemical methods can be considered to be a nuclear protein in vivo. Although this assumption will hold true for most of the analyzed proteins, it could also lead to false interpretations. We analyzed the subcellular distribution of endogenous and plasmid-borne proteins derived from the retrotransposon TRE5-A of Dictyostelium discoideum. In biochemical fractionation experiments the proteins encoded by TRE5-A open reading frame 1 (ORF1p) and the putative endonuclease encoded in ORF2 (ENp) were found in the detergent-insoluble material containing the nuclei. However, salt extraction of isolated nuclei did not considerably release the TRE5-A proteins. Instead, the TRE5-A proteins were strongly enriched in a fraction that contained the chromosomal DNA after removal of most cytoskeletal and histone proteins. These observations implied that ORF1p and ENp were both attached to chromatin in vivo, but this conclusion was disproved by the expression of genetic fusions of green fluorescent protein with either ORF1p or ENp. We show conclusive evidence that both fusion proteins were located as large aggregates of native protein in the cytoplasm of D. discoideum cells.

Animals↗
PubMed2001

Pathogenicity islands: the tip of the iceberg.

Pathogenicity islands represent distinct genetic elements encoding virulence factors of pathogenic bacteria. Pathogenicity islands belong to the class of genomic islands, which are common genetic elements sharing a set of unifying features. Genomic islands have been acquired by horizontal gene transfer. In recent years many different genomic islands have been discovered in a variety of pathogenic as well as non-pathogenic bacteria. Because they promote genetic variability, genomic islands play an important role in microbial evolution.

Animals↗
PubMed2001

Isolation and phylogenetic analysis of bacteria with antimicrobial activities from the Mediterranean sponges Aplysina aerophoba and Aplysina cavernicola.

The aim of this study was to isolate bacteria with antimicrobial activities from the marine sponges Aplysina aerophoba and Aplysina cavernicola. The obtained 27 isolates could be subdivided into eight phylogenetically different clusters based on comparative sequence analysis of their 16S rDNA genes. The sponge isolates were affiliated with the low (Bacillus) and high G+C Gram-positive bacteria (Arthobacter, Micrococcus), as well as the alpha-Proteobacteria (unknown isolate) and gamma-Proteobacteria (Vibrio, Pseudoalteromonas). One novel Bacillus species was identified and two species were closely related to previously uncharacterized strains. Isolates with antimicrobial activity were numerically most abundant in the genera Pseudoalteromonas and the alpha-Proteobacteria. The sponge isolates show antimicrobial activities against Gram-positive and Gram-negative reference strains but not against the fungus Candida albicans. A general pattern was observed in that Gram-positive bacteria inhibited Gram-positive strains while Gram-negative bacteria inhibited Gram-negative isolates. Antimicrobial activities were also found against clinical isolates, i.e. multi-resistant Staphylococcus aureus and Staphylococcus epidermidis strains isolated from hospital patients. The high recovery of strains with antimicrobial activity suggests that marine sponges represent an ecological niche which harbors a hitherto largely uncharacterized microbial diversity and, concomitantly, a yet untapped metabolic potential.

Journal Article↗
PubMed2000

Symbiosis and pathogenesis: evolution of the microbe-host interaction.

Symbiotic and pathogenic bacteria have in common that they live in or on host organisms or host cells. To make a successful living in eukaryotic hosts, bacteria must possess the traits to recognize a given host and establish adherence. When the bacterial location is internal or intracellular, they must further have the ability to invade, to establish a niche, and finally to multiply within a host. The underlying mechanisms which allow this form of existence show similarities between symbiotic and pathogenic bacteria. The final outcome, however, may result in a wide spectrum of consequences for the host ranging from the acquisition of novel metabolic pathways to damage or death. Despite the vastly different forms of interactions, symbiotic and pathogenic bacteria have in common that they are adapted to a particular environmental niche represented by the host organism or compartment thereof. This contribution reviews the evolutionary forces which have shaped the microbial-host interactions. Particular emphasis is placed on the genetic and molecular mechanisms that drive bacterial evolution in response to the selective pressures of the host environment.

Animals↗
PubMed2000

Common molecular mechanisms of symbiosis and pathogenesis.

Traditionally, symbiotic and pathogenic interactions were considered different manifestations of the bacteria-host interaction. However, the molecular mechanisms that mediate communication between and cellular modulation of the involved partners are quite similar. With this review we aim to contribute to a reduction of the traditional gap between symbiosis and pathogenesis research.

Animals↗
PubMed2000

Fluorometric analysis of DNA unwinding (FADU) as a method for detecting repair-induced DNA strand breaks in UV-irradiated mammalian cells.

Fluorometric analysis of DNA unwinding (FADU assay) was originally designed to detect X-ray-induced DNA damage in repair-proficient and repair-deficient mammalian cell lines. The method was modified and applied to detect DNA strand breaks in Chinese hamster ovary (CHO) cells exposed to ionizing radiation as well as to UV light. Exposed cells were allowed to repair damaged DNA by incubation for up to 1 h after exposure under standard growth conditions in the presence and in the absence of the DNA synthesis inhibitor aphidicolin. Thereafter, cell lysates were mixed with 0.15 M sodium hydroxide, and DNA unwinding took place at pH 12.1 for 30 min at 20 degrees C. The amount of DNA remaining double-stranded after alkaline reaction was detected by binding to the Hoechst 33258 dye (bisbenzimide) and measuring the fluorescence. After exposure to X-rays DNA strand breaks were observed in all cell lines immediately after exposure with subsequent restitution of high molecular weight DNA during postexposure incubation. In contrast, after UV exposure delayed production of DNA strand break was observed only in cell lines proficient for nucleotide excision repair of DNA photoproducts. Here strand break production was enhanced when the polymerization step was inhibited by adding the repair inhibitor aphidicolin during repair incubation. These results demonstrate that the FADU approach is suitable to distinguish between different DNA lesions (strand breaks versus base alterations) preferentially induced by different environmental radiations (X-rays versus UV) and to distinguish between the different biochemical processes during damage repair (incision versus polymerization and ligation).

Animals↗
PubMed1999

Coordinate intracellular expression of Salmonella genes induced during infection.

Salmonella typhimurium in vivo-induced (ivi) genes were grouped by their coordinate behavior in response to a wide variety of environmental and genetic signals, including pH, Mg2+, Fe2+, and PhoPQ. All of the seven ivi fusions that are induced by both low pH and low Mg2+ (e.g., iviVI-A) are activated by the PhoPQ regulatory system. Iron-responsive ivi fusions include those induced under iron limitation (e.g., entF) as well as one induced by iron excess but only in the absence of PhoP (pdu). Intracellular expression studies showed that each of the pH- and Mg2+-responsive fusions is induced upon entry into and growth within three distinct mammalian cell lines: RAW 264.7 murine macrophages and two cultured human epithelial cell lines: HEp-2 and Henle-407. Each ivi fusion has a characteristic level of induction consistent within all three cell types, suggesting that this class of coordinately expressed ivi genes responds to general intracellular signals that are present both in initial and in progressive stages of infection and may reflect their responses to similar vacuolar microenvironments in these cell types. Investigation of ivi expression patterns reveals not only the inherent versatility of pathogens to express a given gene(s) at various host sites but also the ability to modify their expression within the context of different animal hosts, tissues, cell types, or subcellular compartments.

Animals↗
PubMed1999

Emotional stability and facial activity as predictors for pain tolerance.

40 subjects were given the Cold Pressor Test. There were large individual differences in the time subjects were willing to keep their hands immersed in the cold water. Predictors indicated for these differences were sex, emotional stability, and facial activity during the test. Emotional stability was measured by means of questionnaire scales and facial activity by ratings on the basis of videotapes.

Adolescent↗
PubMed1999

[Psychodynamic personality markers of psychotherapists in relation to therapy outcome].

In the Berlin psychotherapy study data were collected not only from the patients but also from the therapists. Thus, the influence of personality variables of the therapists on the multidimensionally registered therapy success could be studied. To this end a nonlinear k-sets canonical analysis was applied resulting in a sample-specific optimal scaling. The relationship pattern of the two sets of variables found was satisfactory as regards the internal criteria of the programme as well as its clinical meaningfulness. The results can be used in similar studies for specifying therapist-related hypotheses.

Adult↗
PubMed1997

Bacterial infection as assessed by in vivo gene expression.

In vivo expression technology (IVET) has been used to identify > 100 Salmonella typhimurium genes that are specifically expressed during infection of BALB/c mice and/or murine cultured macrophages. Induction of these genes is shown to be required for survival in the animal under conditions of the IVET selection. One class of in vivo induced (ivi) genes, iviVI-A and iviVI-B, constitute an operon that resides in a region of the Salmonella genome with low G+C content and presumably has been acquired by horizontal transfer. These ivi genes encode predicted proteins that are similar to adhesins and invasins from prokaryotic and eukaryotic pathogens (Escherichia coli [tia], Plasmodium falciparum [PfEMP1]) and have coopted the PhoPQ regulatory circuitry of Salmonella virulence genes. Examination of the in vivo induction profile indicates (i) many ivi genes encode regulatory functions (e.g., phoPQ and pmrAB) that serve to enhance the sensitivity and amplitude of virulence gene expression (e.g., spvB); (ii) the biochemical function of many metabolic genes may not represent their sole contribution to virulence; (iii) the host ecology can be inferred from the biochemical functions of ivi genes; and (iv) nutrient limitation plays a dual signaling role in pathogenesis: to induce metabolic functions that complement host nutritional deficiencies and to induce virulence functions required for immediate survival and spread to subsequent host sites.

Adhesins, Bacterial↗
PubMed1997

Therapeutic alliance and transference: an exploratory study of their empirical relationship.

Transference and the formation of a therapeutic alliance were studied in 126 patients from the Berlin psychotherapy project. The working hypothesis was that the internalized mother and father image would have an influence on the therapeutic alliance. The therapist rated the development of the therapeutic alliance at two points in time. When the parents' images and the therapist image were compared by using difference and similarity measures, four mother and four father types could be constructed of which some showed significant differences in the formation of therapeutic alliance. The introduction and the discussion are focused on the question as to what extent the psychoanalytic assumptions of transference can be useful in empirical therapy research for the construction of new variables and the explanation of social interactions between the two partners.

Adult↗
PubMed1996

Basic cultural values and differences in attitudes towards health, illness and treatment preferences within a psychosomatic frame of reference.

BACKGROUND: Regarded from a biopsychosocial point of view, a culturally determined differential impact of values, lifestyles and attitudes can be expected on health and illness concepts, exerting a potential influence on the general satisfaction with the health care system as well as on subjective treatment preferences. METHODS: 57 men and 63 women between 16 and 86 years of age in the Netherlands and 45 men and 39 women aged between 15 and 78 years in Japan took part in the study. Questions to the subjects were not exclusively restricted to medical care but comprised the potential relationship between health and illness on the one hand, and lifestyles, values, attitudes and treatment preferences on the other. On the basis of previous experience with data from the Dutch sample 27 questions were selected and, using the whole sample, submitted to a factor analysis. Furthermore subjective health and illness attributions were compared by means of a projective technique. RESULTS: The factor analysis resulted in five dimensions: relaxation, work, hedonistic goals versus social status, family life versus career making, alternative versus conventional medical care, with three significant differences between the two countries and two significant gender effects. The projective technique revealed two cultural differences in illness attributions. CONCLUSIONS: The implications of these results for possible health promotion campaigns and a differential choice of health-care strategies are discussed from within a psychosomatic frame of reference. It is hypothesized that the revealed differences can also be useful for attempts at a group-specific increase of acceptance and compliance of certain treatments.

Adolescent↗
PubMed1996

The contribution of nitrate respiration to the energy budget of the symbiont-containing clam Lucinoma aequizonata: a calorimetric study

Heat production and nitrate respiration rates were measured simultaneously in the gill tissue of Lucinoma aequizonata. This marine bivalve contains chemoautotrophic, intracellular, bacterial symbionts in its gill tissue. The symbionts show constitutive anaerobic respiration, using nitrate instead of oxygen as a terminal electron acceptor. An immediate increase in heat production was observed after the addition of nitrate to the perfusion medium of the calorimeter and this was accompanied by the appearance of nitrite in the effluent sea water. The nitrate-stimulated heat output was similar under aerobic and anaerobic conditions, which is consistent with the constitutive nature of nitrate respiration. The amount of heat released was dependent on the concentration of nitrate in the perfusion medium. At nitrate concentrations between 0.5 and 5 mmol l-1, the total heat production was increased over twofold relative to unstimulated baseline values. A mean (±s.e.m.) experimental enthalpy of -130±22.6 kJ mol-1 nitrite (N=13) was measured for this concentration range.

Journal Article↗
PubMed1996

Defensive and affective-emotional reactions to war: the Abkhazian war as reflected in people's subjective reactions.

Differences in defensive and affective-emotional reactions of 108 male Georgian subjects who had been confronted with the consequences of the Abkhazian war in different ways (nonwounded soldiers, wounded soldiers, and civilian controls) were significant between groups on all defense scales and four of the 12 Gottschalk-Gleser scales. The results are discussed from a perspective with war forming for all three groups an important life event which differentially determined their psychological reactions.

Adaptation, Psychological↗