Biomedical subjects

M Hartung

Publications and source records attributed to M Hartung.

At least 19 recordsLinked to original sources

PubMed2002

A star in a 15.2-year orbit around the supermassive black hole at the centre of the Milky Way.

Many galaxies are thought to have supermassive black holes at their centres-more than a million times the mass of the Sun. Measurements of stellar velocities and the discovery of variable X-ray emission have provided strong evidence in favour of such a black hole at the centre of the Milky Way, but have hitherto been unable to rule out conclusively the presence of alternative concentrations of mass. Here we report ten years of high-resolution astrometric imaging that allows us to trace two-thirds of the orbit of the star currently closest to the compact radio source (and massive black-hole candidate) Sagittarius A*. The observations, which include both pericentre and apocentre passages, show that the star is on a bound, highly elliptical keplerian orbit around Sgr A*, with an orbital period of 15.2 years and a pericentre distance of only 17 light hours. The orbit with the best fit to the observations requires a central point mass of (3.7 +/- 1.5) x 10(6) solar masses (M(*)). The data no longer allow for a central mass composed of a dense cluster of dark stellar objects or a ball of massive, degenerate fermions.

Journal Article↗

PubMed2002

Chemiluminescent immunoassay as a microtiter system for the detection of Salmonella antibodies in the meat juice of slaughter pigs.

Chemiluminescent immunoassay (CLIA) was applied in the screening of swine meat juice samples obtained from different laboratories in Germany, using the indirect enzyme linked immunosorbent assay (ELISA) as test for comparison. Out of the 1350 samples tested, 987 were found acceptable for validation of results. A good level of agreement between the two tests was obtained with a kappa value of 0.824 at 20% cut-off and 0.798 at 40% cut-off. At 20% and 40% cut-off levels, a sensitivity of 96.2% and 97.3%, respectively, and a specificity of 94.6% and 95.1%, respectively, were demonstrated between CLIA and ELISA. The detecting lipopolysaccharide (LPS) antigen was tested for specificity and a cross-reaction with two Escherichia coli and Yersinia strains was found when tested with ELISA. This reaction was not observed in CLIA, possibly because of the broader measurement spectrum of this test, which allows a more distinctive definition of immunologic reactions. The same explanation can be given for the increased number of meat juice samples which were positively detected only in ELISA but not in CLIA. Because of the wide detection range in CLIA, a normalization scheme was necessary to obtain reproducible results in this test system. The samples positively classified in screening were further tested for reciprocal titres in both test systems, and a higher correlation between screening and titration results was obtained for CLIA. Based on the results of this study, CLIA can be used as a reference method in detecting Salmonella antibodies in the meat juice of slaughter pigs.

Animals↗

PubMed2001

Analyses of spontaneous mutations of cloned gene 49 of phage T4.

Holliday structure resolving enzyme endonuclease VII (endo VII) of phage T4 is highly toxic for E. coli when expressed outside of the phage infection environment. As a consequence, plasmids with a mutated gene 49, the gene which encodes for endo VII, can be easily isolated and characterised. We have isolated and characterised 400 survivors from independent transformations with a plasmid carrying gene 49 under the control of the T7 promoter. The majority had mutated gene 49 by IS10 insertions which almost exclusively mapped to a distinct site. When this site was mutated other insertion sites were observed as well as an increase in other mutational events including large deletions. Neither of the observed insertion sites mapped matched the consensus IS10 sequence completely. Additionally when the level of expression of gene 49 was altered the distribution of mutations was changed suggesting that other elements apart from the target sequence are necessary for determining IS10 insertion. The expression of gene 49 in E. coli provides a particularly useful tool for the analysis of mutational events.

Bacteriophage T4↗

PubMed2000

Advances in light curing.

PURPOSE: To review and connect the scientific background of light curing with clinical requirements and new technical opportunities in order to conclude the best technology for next generation light curing units. RESULTS: Three conclusions are drawn for proper light curing: (1) A minimum dose of light is needed (wavelength dependent); (2) Internal stress can be reduced by giving the sample time to flow before gel point is reached; (3) An upper intensity limit has to be respected to limit temperature increase as well as light intensity dependent deactivation of activated photoinitiators. These conclusions can best be realized by using the softstart approach. A comparison of different light generation technologies shows that LEDs are most likely to shape the next generations of curing lights. Due to their superior power conversion rate as well as to their optimum spectral emission small and handy devices can be realized that work battery-powered and totally silent. The benefits for the dentist are improved reliability, handling, and hygiene.

Dental Materials↗

PubMed1999

Simplified preparation of a specific S. enteritidis antigen for ELISA and other immunological techniques.

This study was conducted to prepare a specific S. enteritidis antigen (FG-Antigen) for the serological detection of S. enteritidis infections in chicken flocks. This antigen (FG-Antigen) consistent mainly of the flagellar fraction H:g and partly of the fimbrial fraction SEF14 from a S. enteritidis-phage type 4 strain. The initial steps followed in the preparation of this antigen were conducted based on a previously described procedure, which involved the application of heat at 60 degrees C. The purification process (filtration and concentration) enabled the exclusion of the cross-reaction causing LPS antigens from the preparation and allowed the retention of S. enteritidis-specific antigens composed of fimbria and H:g fractions. As a result, no cross-reaction with S. typhimurium nor with S. gallinarum was exhibited by the prepared FG-antigen. To characterize and determine its specificity, the following laboratory tests were conducted: indirect ELISA, immunoblotting and a SEF14 agglutination test. In these examinations, rabbit and chicken reference sera as well as chicken field sera and absorbed hyperimmune sera against H:g-carrying serovars were used.

Agglutination Tests↗

PubMed1999

Detection of antibodies to S. enteritidis in broilers by means of indirect ELISA and chemiluminescent immunoassay (CLIA).

This study was conducted to develop a serological detection system for the monitoring of broiler flocks for Salmonella enteritidis infections. A specific S. enteritidis antigen (FG-Antigen) was used to compare the sensitivity and the specificity of the chemiluminescent immunoassay (CLIA) with those of the indirect ELISA. This comparison was performed using a total of 578 sera, which, depending on the microbiological and vaccination history, were categorized into groups. Most of the serum samples which were classified as positive showed higher titers in CLIA than in ELISA. Using the prevalence of positive reactors, significant differences between Groups were additionally demonstrated. The absorbance values of the passively immunized group showed the highest and those of the Salmonella-negative group the lowest correlation-coefficient. Using the mean net absorbance of the prevalence group, the ELISA system exhibited a sensitivity of 100% and a specificity of 96.2%, while CLIA had a sensitivity and a specificity of 85.7% and 96.2%, respectively. ELISA and CLIA can be used in the examination of non vaccinated flocks for S. enteritidis-infections as alternative to the bacteriological culture method. CLIA is distinguished for its fast and convenient procedure as well as for its wider measurement spectrum, while the indirect ELISA is almost as efficient as CLIA and requires less investment.

Animals↗

PubMed1999

[Attempt to estimate the share of human Salmonella infections, which are attributable to Salmonella originating from swine].

On the basis of the data obtained in 1996 and 1997 in Germany on the frequency of detection of Salmonella and also of single Salmonella serovars in foods and infected humans, attempts were made to assess the relevance of Salmonella from swine as a source of human infection. Four assumptions considered as reasonable were made concerning the development of human salmonellosis. On the basis of these assumptions, a model for the estimation of the share of human Salmonella infections attributable to the swine population is proposed. According to this, ca. 20% of human cases of salmonellosis have been caused by Salmonella originating from swine.

Animals↗

PubMed1998

Cre mutants with altered DNA binding properties.

The recombinase Cre of bacteriophage P1 is a member of the family of site-specific recombinases and integrases that catalyze inter- and intramolecular DNA rearrangements. To understand how this protein specifically recognizes its target sequence, we constructed Cre mutants with amino acid substitutions in different positions of the presumptive DNA binding region. Here we present the results of in vitro DNA binding and in vivo recombination experiments with these Cre mutants. Most substitutions of presumptive DNA-binding amino acids in in vitro tests resulted either in the loss of target binding or in a broadening of target recognition specificity. Of the mutations resulting in a broadening of target specificity, one, N317A, results in a reduced recombination efficiency with the wild-type loxP target but recombines, in contrast to wild-type Cre, in in vivo experiments, with a symmetric variant of the wild-type target sequence. This target variant differs from wild-type loxP by the symmetric C to A replacement in position 6 of the inverted repeats. We propose a common multihelical DNA binding motif for the family of integrases and recombinases. This model implies a major structural rearrangement for the DNA binding region of lambda integrase, analogous to the structural rearrangements of the DNA binding motifs of other proteins when contacting their target DNA.

Bacteriophage P1↗

PubMed1997

Effect of body composition, feed intake, and ambient temperature on heat production of Vietnamese Sway-back pigs.

From theoretical considerations animals with a higher protein-fat ratio in the body should have a higher maintenance energy requirement (MEm). The literature on this problem shows a non-uniform picture with deviating results. From the results of a series of experiments it is possible to compare the heat production (HP) of male and female animals of the Vietnamese Sway-back breed pigs which vary quite widely in their body composition. The protein-fat ratio was 1.2 for the male and 0.2 for the female animals. In the experiments 4 male and 4 female animals in the live weight range of 20-33 kg and 33-42 kg, respectively, were involved. The HP measurements were carried out in climatized respiration chambers on two levels of energy intake at ambient temperatures of 6 degrees C, 12 degrees C, 18 degrees C, 24 degrees C, 30 degrees C, and 35 degrees C. The dependence of HP on the ambient temperature has been described by a cubic regression function. Thermoneutral temperatures are lower in the female animals caused by the better insulation effect of the backfat. The difference in HP which was expected by the large difference in body composition, was not found. The absolute protein mass determined the correlation to HP. Certainly the difference increased after lowering the ambient temperature. The influence of different factors on HP is discussed.

Animals↗

PubMed1996

[Prevalence of motile salmonellae in egg-laying hens at the end of the laying period].

A total of 3504 hens of the layer-type from 122 flocks (belonging to 89 farms), each with more than 10,000 animals, were culturally examined at the time of slaughter. Of these hens, 2112 (60.3%) from 74 flocks (60.7%) were obtained from 21.3% of the laying-hen farms in a selected region of Lower Saxony in Germany. The other hens came from the remaining part of Lower Saxony and seven other German states (Brandenburg, Mecklenburg Vorpommern, North Rhine Westphalia, Schleswig Holstein, Saxony, Saxony Anhalt, and Thuringia). After arrival at the slaughter house, a random sample of 29 layers was collected from each of the flocks, and liver and spleen, as well as cecal samples, were separately cultured for each bird. Motile salmonellae could be proved in 365 (10.4%) layers from 67 flocks (54.9%). In the selected region, 48 out of 74 flocks (64.9%) and 289 out of 2112 layers (13.7%) were Salmonella-positive. However, the isolation frequency of salmonellae did not differ significantly between flocks of brown and white layers. These Salmonella (S.) isolates could be serologically assigned to 6 different serovars, namely S. enteritidis (SE), S. infantis (SI), S. livingstone (SL), S. typhimurium (ST), S. indiana (SID) and S. cerro; only one isolate of serogroup D1 was incompletely serotyped. SE was detected in 5.8% of the hens from 47.5% of the tested flocks, of which 4.6% of the animals and 32.8% of the flocks came from the selected region in Lower Saxony. The SE isolates were classified into 12 different lysotypes. In 41 out of 58 SE-positive flocks (70.7%), the isolates belonged to lysotype (lt) 4, in 12 flocks (20.7%) to lt 8, in 5 flocks (8.6%) to lt 7, and in 3 flocks (5.2%) to lt 11. A total of 190 (93.1%) out of 204 isolates of the serovar SE carried plasmids. All the plasmid-positive SE-strains harboured the serovar-specific 37 MD virulence-plasmid, nine of them (4.4%) in conjunction with a second and eight strains (3.9%) with a second and a third smaller plasmid.

Animals↗

PubMed1994

Nonhomologous DNA end joining of synthetic hairpin substrates in Xenopus laevis egg extracts.

Processes of DNA end joining are assumed to play a major role in the elimination of DNA double-strand breaks (DSB) in higher eucaryotic cells. Linear plasmid molecules terminated by nonhomologous restriction ends are the typical substrates used in the analysis of joining mechanisms. However, due to their limited structural variability, DSB ends generated by restriction cleavage cover probably only part of the total spectrum of naturally occurring DSB termini. We therefore devised novel DNA substrates consisting of synthetic hairpin-shaped oligonucleotides which permit the construction of blunt ends and 5'- or 3'-protruding single-strands (PSS) of arbitrary sequence and length. These substrates were tested in extracts of Xenopus laevis eggs known to efficiently join linear plasmids bearing nonhomologous restriction termini (Pfeiffer and Vielmetter, 1988). Sequences of hairpin junctions indicate that the short hairpins are joined by the same mechanisms as the plasmid substrates. However, the bimolecular DNA end joining reaction was only detectable when both hairpin partners had a minimal duplex stem length of 27bp and their PSS-tails did not exceed 10nt.

Animals↗

PubMed1994

Salmonella enteritidis phage types in Germany.

In order to monitor the epidemiological situation of S. enteritidis in Germany, in 1990-91 1138 isolates from more than 180 locations in West Germany were phage typed. 1124 strains (98.8%) from all sources were typeable, belonging to 21 different phage types (PT). PT4 strains were isolated most frequently (70.8%). In addition, PT7, 25, 34 and 8 were of epidemiological relevance with incidences of 7.2 to 4.5%. The comparison of data shows that in Germany, like in other parts of Europe, PT4 predominates. This phage type is, however, infrequent in North America, where PT8 has the highest incidence.

Animals↗

PubMed1994

Localization of rDNA transcription sites in nucleoli of human Sertoli cells: an EM quantitative autoradiographic study using 3H-uridine.

The sites of rDNA transcription within human Sertoli cell nucleoli have been localized using EM autoradiography after a 45-min pulse of 3H-uridine and an exposure time of 6 months. Two successive quantitative image analyses, one derived from the 50% probability circle method and the other from the cross-fire method, allowed us to estimate the radioactivity incorporated within each nucleolus compartment. This study demonstrated that rDNA transcription occurred mainly at the border between fibrillar centers and dense fibrillar components and to a lesser extent within the dense fibrillar component. The other Sertoli cell nucleoli compartments did not incorporate 3H-uridine and therefore were not involved in rDNA transcription.

Autoradiography↗

PubMed1993

[Occurrence of enteritis-causing salmonellae in food and in domestic animals in 1991].

The control of salmonellae in foods and animals in Germany, 1991, is based on voluntary contributions of veterinary institutions, e. g. governmental investigation centres, universities, agricultural institutions and slaughter-house laboratories. The results of questionnaire-based evaluations are presented (s. a. HARTUNG, 1993 a). Also reported were 101 outbreaks involving 2272 cases of salmonellosis (fig. 1), of which 92% were caused by S. enteritidis. 46% of the cases were caused by egg and egg-containing meals, 24% by bakery products, often containing raw eggs. From poultry meat the organism was only isolated in less than 1% of the known cases. Meat and meat products (10%) and milk (5%) were further sources of infection. Summarizing it can be assumed that in 70% of the cases the cause of foodborne salmonellosis were meals prepared with raw eggs. The mean salmonella rate in routine food investigations was 0.88% (tab. 1). Poultry had a salmonella rate of 13% and eggs, incl. egg-containing dishes, a rate of 1%. All other food groups were contaminated with salmonella at the level of the mean rate (meat and meat products) or less (fish and milk and their products: 0.1%). The mean salmonella rate in diagnostic examinations of domestic animals was 5.77% (tab. 2). Cattle and chicken showed salmonella rates at the level of the mean rate, whereas pig, sheep, goats and equines showed much lower levels. On the other hand "other poultry" (9.5%) and especially chicks (13%) had higher levels of salmonella.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Human ribosomal RNA gene repeats are localized in the dense fibrillar component of nucleoli: light and electron microscopic in situ hybridization in human Sertoli cells.

The distribution of the human ribosomal gene repeat within human Sertoli cell nucleoli was investigated with the help of DNA-DNA in situ hybridization at the light and electron microscopic level. Probes from both the transcribed part of the gene repeat and the "non-transcribed" spacer were found to hybridize predominantly to the dense fibrillar component of nucleoli. It therefore can be concluded that the dense fibrillar component of nucleoli is the major site of the intranucleolar location of the ribosomal DNA. This holds true not only for the dense fibrillar component adjacent to fibrillar centers, but also for the dense fibrillar component remote from the fibrillar centers.

Cell Nucleolus↗

PubMed1991

Nucleoli, nucleolar chromosomes and ribosomal genes in the human spermatocyte.

The formation and development of nucleoli and their connections with the nucleolar chromosomes were studied in human spermatocytes using electron microscopy, silver staining of nucleolus organizer regions (NORs), high resolution autoradiography and in situ hybridization in order to localize rRNA genes and their transcription in the different stages of meiotic prophase I. At leptotene, new nucleoli were formed, consisting of a fibrillar centre surrounded by a cap of dense fibrillar component. Following [3H]uridine uptake, label was found only over the dense fibrillar component. In situ hybridization revealed rDNA mainly in the dense fibrillar component and in the chromatin. During zygotene, nucleoli increased in size. The fibrillar centre was connected with the secondary constriction region of the nucleolar bivalent and was partially surrounded by dense fibrillar component. This shell of dense fibrillar component merged into a fibrillo-granular mesh that extended away from the fibrillar centre. Autoradiography following [3H]uridine uptake again showed the label overlaying the dense fibrillar component and the proximal part of the fibrillo-granular strands. With in situ hybridization in both the light and electron microscope, signal was mainly found in the dense fibrillar component. A small quantity of label was observed in the peripheral region of the fibrillar centre and in the adjacent chromatin. From early to late pachytene segregation of nucleolar components occurred, with a reduction in the dense fibrillar component that formed a narrow rim around the fibrillar centre with small extensions along the granular component. [3H]uridine incorporation progressively decreased. In situ hybridization showed signal located mainly in the dense fibrillar component and in the chromatin corresponding to the condensed short arm of the nucleolar bivalent. Our results indicate that the majority of rDNA is located and transcribed in the dense fibrillar component; only a small amount is present in the peripheral part of the fibrillar centre and may be transcribed there. Moreover, from leptotene to zygotene, rDNA unravels from the nucleolar chromosome into the nucleolar dense fibrillar component. From zygotene to late pachytene a progressive return to the condensed acrocentric short arm is observed.

Autoradiography↗

PubMed1991

Crossed immunoelectrophoresis applied to representative strains from 11 different Pasteurella species under taxonomic aspects.

Crossed immunoelectrophoresis evaluated on a numerical basis revealed a close antigenic relationship between species of the genus Pasteurella. By cluster analysis, 4 groups on similarity levels between 87% and 72% S could be separated which were connected by a minimum level of 69.5% S. One subgroup included all biovars or subspecies consisting of strains with mucoid growth. Another feature governing the antigenic relationship seemed to be the host range of Pasteurella species. Despite a considerable number of cross-reacting antigens, representative strains of the genera Haemophilus and Actinobacillus were clearly separated from Pasteurella. Similarly, "Pasteurella" haemolytica and Taxon 16 strains tested did not belong to this genus. An Escherichia coli strain showed a higher number of cross-reacting antigens, confirming known antigenic relationship among Gram-negative bacterial species.

Animals↗

PubMed1991

Transcribed and nontranscribed parts of the human ribosomal gene repeat show a similar pattern of distribution in nucleoli.

The distribution pattern of the transcribed and nontranscribed parts of human ribosomal RNA genes were visualized simultaneously in the same cells by nonautoradiographic in situ hybridization. DNA probes labeled with either digoxigenin or biotin were detected in the same cells by different fluorescence systems. The signals from both the transcribed and nontranscribed parts showed a similar distribution pattern. This finding is not compatible with the conclusion, suggested by earlier studies, that the transcribed and nontranscribed parts of the rRNA genes are located at different sites within the nucleoli or in different nucleolar components.

Cell Nucleolus↗