UV Pre-Treatment for Polycarbonate for Bonding LSR in a Multi-Component Injection Molding Process

In this study, the influence of UVC radiation and the influence of ozone on the surface energy of specimens made of polycarbonate were investigated. In an additional step, the peeling resistance of silicone flaps, which were overmolded, onto pre-treated PC plates of multicomponent specimens were analyzed. For this purpose, the samples were exposed to UVC radiation for different lengths of time, ranging from 5 s to 3 600 s. To further evaluate the influence of the ozone created by the UVC in the presence of oxygen, treatments were also performed in pure oxygen and nitrogen atmospheres. Contact angle measurements as well as analyses of the surface roughness were carried out to evaluate the effect of the treatment. Two phenomena were identified during the investigations. In room air and oxygen atmospheres, a short-term effect of UVC radiation was observed, which led to an increase in the surface energy, and, therefore, also to an increase in the wettability after an exposure time of only 10 s. In addition, a long-term effect was also found when tests were performed in a nitrogen atmosphere. This effect became visible after at least 60 s, and increased over the course of the duration exposure. The surface roughness of the polycarbonate plates increased up to about 60 % after 10 s of UVC exposure time in an air atmosphere, after 300 s of exposure to UVC radiation the roughness values had more than doubled. A modular injection molding tool was designed for the production of multi-component specimens. In this tool, a thermoplastic plate is molded on the one side, and is then automatically transferred by a robot system to be overmolded with silicone on the other side. The employed injection molding technique makes an intermediate treatment, such as surface activation of the thermoplastic plate, possible before it is overmolded. Also, the short-term and long-term effects of UVC treatment were able to be verified again for the peeling resistance of the material. These tests were only carried out for specimens treated in air.

Quo vadis? - Monitoring Campylobacter in Germany

Campylobacter is a poorly recognized foodborne pathogen, leading the statistics of bacterially caused human diarrhoea in Europe during the last years. In this review, we present qualitative and quantitative German data obtained in the framework of specific monitoring programs and from routine surveillance. These also comprise recent data on antimicrobial resistances of food isolates. Due to the considerable reduction of in vitro growth capabilities of stressed bacteria, there is a clear discrepancy between the detection limit of Campylobacter by cultivation and its infection potential. Moreover, antimicrobial resistances of Campylobacter isolates established during fattening of livestock are alarming, since they constitute an additional threat to human health. The European Food Safety Authority (EFSA) discusses the establishment of a quantitative limit for Campylobacter contamination of broiler carcasses in order to achieve an appropriate level of protection for consumers. Currently, a considerable amount of German broiler carcasses would not comply with this future criterion. We recommend Campylobacter reduction strategies to be focussed on the prevention of fecal contamination during slaughter. Decontamination is only a sparse option, since the reduction efficiency is low and its success depends on the initial contamination concentration.

Reversible mass exchange between two multicomponent systems of different temperatures

The concept of reversible work in nonequilibrium systems, which has been used for the derivation of thermal diffusion coefficients, is critically examined. For this purpose heat and mass exchange between two multicomponent systems of different temperatures and pressures is treated in detail. It is shown both by general considerations and by a specific example that calculating the reversible work--the work performed in case of reversible mass exchange--is essentially the same as calculating the dissipation function describing the corresponding irreversible process. Although the dissipation function is the starting point for the description of irreversible processes in nonequilibrium thermodynamics, it is not obvious how it could be used to obtain an expression for the thermal diffusion coefficient.

[Intersectoral collaboration of institutions in Germany and Europe in the field of food-borne zoonoses]

Prevention and control of food-borne zoonoses is given high priority in Germany and in the European Union. To implement targeted control measures, detailed data are necessary on human zoonoses and on the prevalence of zoonotic agents along the food chain. EU-wide legislations have been stipulated that allow collection and collation of relevant data across member states. The necessary structures have been established and are being constantly refined. In addition, surveillance systems and early warning systems have been improved or set up, respectively, to timely investigate and control food-borne outbreaks and to transnationally communicate food safety risks. For prevention and control to be effective, well-defined responsibilities and close collaboration of public health, veterinary public health and food safety authorities are needed. This report reviews the pertinent legislation, the established structures, and the collaboration of competent authorities in Germany and particularly in Europe. In the future, data quality and collaboration on national and EU levels will likely be further improved. Targeted control measures, particularly at primary production, are expected to lead to a sustainable reduction of the incidence of food-borne zoonoses.

ANKOM – a new instrument for the determination of fat in muscle and meat cuts – a comparison

Abstract. The objective of this study was to compare the new fat extraction equipment ANKOMXT15 Extractor with different chemical and physical methods which are widely used to determinate the fat content of different animal tissues. In total 23 pigs and 19 cattle were included in the investigations. Different cuts of the carcasses like longissimus muscle (MLD), head, belly and breast, feet, ham, neck, loin, tenderloin and subcutaneous fats were used for this comparison. The investigation compared following three chemical methods: classic Soxhlet method, automatic fat extraction (ANKOMXT15 Extractor), automatic fat extraction following hydrolysing (ANKOMHCL Hydrolysis System, ANKOMXT15 Extractor) and two physical methods: Infratec1255 Food and Feed Analyzer and FoodScan™ Lab (FOSS). For accurate statistical analysis the different cuts were ordered into three fat groups. The repeatability (θ) of the chemical methods was calculated, which ranged between 0.88–1.00. No significant differences were measured between the new tested device ANKOMXT15 Extractor and the Soxhlet method. The use of the ANKOMXT15 Extractor is recommended because of the high precision, low purchase and using costs, and shorter analyses time.

Non-invasive determination of body composition in pigs using a Norland XR-26 bone densitometer

Abstract. Non-invasive measurement of body composition provides advantages in growth studies compared to conventional techniques. The same individual can be measured several times, the measurement is faster, and the number of pigs required as well as the random effect of animal are reduced. The aim of the present study was to determine the composition of the half carcass and of the ham/shank region by a whole body dual-energy X-ray absorptiometry (DXA) scan of the live pig using a Norland XR-26. Accuracy and precision of DXA measurement were evaluated by regression analysis between DXA-derived values and chemical analysis as well as dissection. Pigs of different gender were used covering a wide range of body weights and body composition. Single regression analysis for lean and fat mass revealed a close relationship between half carcass DXA and chemical analysis (R² = 0.97 and R² = 0.91, respectively) as well as dissection (R² = 0.99 and R² = 0.98, respectively). The prediction accuracy (R²) was lower for the tissue percentages than for the respective tissue masses. The relationship between live pig DXA and reference methods was close for dissected lean meat (R² = 0.90) and adipose tissue mass (R² = 0.93). For chemical lean and fat mass, R² were slightly lower. Multiple regression analysis using one to four independent variables improved accuracy of prediction. The composition of ham and shank could be predicted more accurately than the half carcass composition.

Optical cell with periodic resistive heating for the measurement of heat, mass, and thermal diffusions in liquid mixtures

A new technique for the measurement of heat, mass, and thermal diffusions in liquids has been developed. Similar to laser induced dynamic gratings, a temperature grating is created in the sample. Thermal expansion transforms the temperature into a refractive-index grating, which is read by diffraction of a readout laser beam. In a multicomponent mixture an additional concentration grating is formed by thermal diffusion driven by the temperature gradients of the temperature grating. Differently to laser induced dynamic grating experiments we use Joule heating instead of optical heating. For that purpose we have built cuvettes which have a grating of transparent conducting strips on the inner side of one of their windows. If heated by an electric current a temperature grating will build up in the sample. Both the heat equation and the extended diffusion equation have been solved in two dimensions to allow for quantitative data analysis. Our apparatus and method of analysis have been validated by measurements of heat, mass, and thermal diffusions in pure and binary liquids. Heat diffusion can be correctly determined as was shown for pure toluene, pure dodecane, and the symmetric mixture of isobutylbenzene dodecane. Mass and thermal diffusions were studied in the three symmetric mixtures of dodecane, isobutylbenzene, and tetralin. The obtained diffusion and Soret coefficients agree with the literature values within the experimental errors. Uncompensated transient heating effects limit the resolution of the experimental technique.

Correlation between thermal diffusion and solvent self-diffusion in semidilute and concentrated polymer solutions

We have performed measurements of thermal diffusion coefficients DT and solvent self-diffusion coefficients Dss in semidilute to concentrated polymer solutions. Solutes of different glass transition temperatures and solvents of different solvent qualities have been used. The investigated systems are in detail: poly(dimethyl-siloxane) in toluene, tristyrene in toluene, polystyrene in toluene, polystyrene in tetrahydrofuran, polystyrene in benzene, and polystyrene in cyclohexane. The thermal diffusion data are compared to our data and literature data for solvent self-diffusion coefficients. In all systems the concentration dependence of DT closely parallels the one of Dss which may be viewed as a local probe for friction on a length scale of the size of one polymer segment. This identifies local friction as the dominating parameter determining the concentration dependence of DT. Solvent quality, in contrast, has no influence on DT.

Thermal diffusion of dilute polymer solutions: The role of solvent viscosity

We have performed measurements of the thermal diffusion coefficient D(T) in the dilute limit on polystyrene in cyclo-octane, cyclohexane, benzene, toluene, tetrahydrofuran, ethyl acetate, and methyl ethyl ketone and of poly(dimethyl-siloxane) in toluene. These data have been combined with literature data to test various theoretical predictions. The viscosity is identified as the dominating and only relevant solvent parameter. On the polymer side, the size or mass of an effective correlated segment determines the strength of the Soret effect. Large and heavy effective segments, as found in stiffer chains, lead to higher D(T).

The role of heat-conducting walls in the measurement of heat and mass transport in transient grating experiments

We present a two-dimensional model to account for the role of heat-conducting walls in the measurement of heat transport and Soret-effect--driven mass transport in transient holographic grating experiments. Heat diffusion into the walls leads to non-exponential decay of the temperature grating. Under certain experimental conditions it can be approximated by an exponential function and assigned an apparent thermal diffusivity D(th, app)<D(th, s), where D(th,s) is the true thermal diffusivity of the sample. The ratio D(th, app)/D(th, s) depends on only three dimensionless parameters, d/l(s), kappa(s)/kappa(w), and D(th, s)/D(th, w). d is the grating period, l(s) the sample thickness, kappa(s) and kappa(w) the thermal conductivities of sample and wall, respectively, and D(th,w) the thermal diffusivity of the wall. If at least two measurements are performed at different d /l(s), both D(th,s) and kappa(s) can be determined. Instead of costly solving PDEs, D(th,s) can be obtained by finding the zero of an analytic function. For thin samples and large grating periods, heat conduction into the walls plays a predominant role and the concentration grating in binary mixtures is no longer one-dimensional. Nevertheless, the normalized heterodyne diffraction efficiency of the concentration grating remains unaffected and the true thermal and collective diffusion coefficient and the correct Soret coefficient are still obtained from a simple one-dimensional model.

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.

Mast-, Schlachtleistung und Fleischqualität verschiedener Schweinerassen bei Stall- und Freilandhaltung (Kurzmitteilung)

Abstract. Title of the paper: Fattening, slaughter performance and meat quality of different pig breeds in indoor or outdoor housing (short communication) Relationships between outdoor housing and some meat quality parameters were investigated. Studies were carried out with the pig breeds Schwerfurter Fleischrasse, Deutsches Sattelschwein und Duroc. Fattening, slaughter performances and meat quality were compared by indoor or outdoor housing. Between different breeds in most parameters there were significant differences. Regarding the influence of outdoor housing with grazing the study showed improve results by meat quality parameters only in meat colour and water keeping.

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.

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.

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.

Verlauf von biochemischen Kennwerten im Blut von Schweinen mit unterschiedlicher Fettansatzleistung

Abstract. Title of the paper: Level of the metabolic substances in blood in relation to the development of pigs with different capacity for lipid deposition 28 German Saddle Back pigs (DS) and 30 German Landrace pigs (DL) were used to determine the concentrations of 16 Substrates and enzymes in the blood plasma during the growing-finishing period. Blood samples were taken from veno cava cranialis all two weeks 24 hours after Myostress injection. For the characterization of breed differences the results were represented as means in relation to the whole trial period and to live weight classes of the pigs. The concentrations of protein, urea, Creatinine, LDL + VLDL cholesterol, GGTP and AP were significantly different between DS and DL both for whole trial period and for most of live weight classes. For urea acid, lactate, triglycerides, HDL cholesterol, ALAT and LDH breed differences were mainly small. The breed differences for the concentrations of glucose, total cholesterol, ASAT and CK were statistically significant in some live weight classes, only.

[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.

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.

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.

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.

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.

[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.

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.

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.

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.

[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)

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.

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.

Yersinia in effluents from the food-processing industry

Yersinia enterocolitica and Yersinia pseudotuberculosis are current sources of pathogenic strains in humans and animals. Yersiniae infections occur throughout the world, but are most prevalent in regions with moderate and subtropical climates. In Australia, Central Europe and North America, cases of human infections with Yersinia enterocolitica now rank in third place. The food-processing industry may influence the epidemiological situation in different ways. Effluents which contaminate the environment may originate from slaughterhouses; e.g. from sewage contaminated with faeces from the lairage or contaminated effluents from the actual slaughter areas. The carcasses may serve as carriers of the organisms to the food-processing plants where they eventually contaminate the processed foods. Rodents and pests may also be carriers. Pathogenic Y. enterocolitica and Y. pseudotuberculosis strains mainly occur in swine and pork. The ability to multiply under refrigeration and in vacuum-packaged products means that pathogenic Y. enterocolitica can cause foodborne diseases. If a plant harbours any pathogenic Yersiniae, transfer of the contaminant to the sewage is possible. Although pathogenic Yersiniae from infected animals can survive in sewage and in surface waters, the role of properly treated sewage in the transmission of yersiniosis seems to be of minor importance. If the recommendations for modern slaughter techniques are properly followed, the spread of pathogens in the slaughterhouses and, subsequently, into other food-processing plants can be minimised.

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.

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.

Suppression of a hind limb flexion withdrawal reflex by microinjection of glutamate or morphine into the periaqueductal gray in the rat

Microinjection into the midbrain periaqueductal gray (PAG) or lateral reticular formation (LRF) of the neuronal excitant glutamate produces analgesia, and suppresses the responses of a fraction of spinal dorsal horn neurons to noxious heat applied to ventral hind paw skin. Microinjection of morphine into the PAG also produces analgesia, but has been reported to frequently facilitate, as well as to suppress or have no effect, on nociceptive spinal neurons. In anesthetized rats, we tested whether (a) glutamate microinjections into PAG or LRF, and (b) morphine microinjections into PAG, affected the isometric force of hind limb withdrawal elicited by the same noxious heat stimuli on the hind paw as used in single-unit studies of dorsal horn neurons. Glutamate (0.5 M; 0.1-0.5 microliter) microinjected at 9/12 PAG and 8/10 LRF sites suppressed the reflex, and had no effect or facilitated the reflex from the remaining sites. Morphine (5 micrograms in 0.5 microliter) microinjected at each of 10 PAG sites suppressed the reflex in a naloxone-reversible manner. Suppression usually began shortly after morphine, peaked at 20-40 min, and lasted greater than 60 min. The integrated flexion reflex thus appears to be more susceptible to chemical midbrain stimulation under these experimental conditions, compared to previous studies of single dorsal horn neurons.

Sequential changes in the nucleoli of human spermatogonia with special reference to rDNA location and transcription

The nucleoli of human spermatogonia were studied using electron microscopy, silver staining, radioautography and in situ hybridization. In all types of A spermatogonia, nucleoli were consistently located at the periphery of the nucleus and contained a single fibrillar center associated with the nuclear envelope. In B spermatogonia, nucleoli were centrally located in the nuclei and showed several fibrillar centers or were found to disintegrate. Nucleolar morphology was found to be a good, though not an unequivocal indicator of spermatogonial type. The observed changes in nucleolar morphology reflect the differentiation of spermatogonia: the nucleolar disintegration seen in B spermatogonia corresponds to a pre-leptotene cessation of rDNA transcription. In radioautographs following 3H-uridine uptake, the label was consistently found over the dense fibrillar component, except in the B spermatogonia with disintegrating nucleoli, where no uptake could be detected. In situ hybridization demonstrated that the distribution of rDNA did not correspond to the site of the fibrillar center but to the dense fibrillar component. Compared with radioautographs, this finding clearly established that transcribed units of rDNA were located in the dense fibrillar component. Silver staining was strongly positive in fibrillar centers and in the dense fibrillar component. In Ap spermatogonia the silver deposit was often localized at the edge of the fibrillar threads. The relationships between silver-stained proteins and transcribed and nontranscribed portions of ribosomal genes are reevaluated.

The excitation of cutaneous nerve endings in a neuroma by capsaicin

Spontaneous electrophysiological activity and excitation by capsaicin of regenerating sensory fibers has been studied using 1 to 20-week-old neuromas induced in rats by ligating and transecting the saphenous nerve. Overall, spontaneous activity occurred in 12% of fibers, and capsaicin at concentrations up to 1.0 microM excited 3.8% of all the A delta-plus C-fibers examined. There was a slight increase in the incidence of spontaneous activity, but not excitation by capsaicin, with increasing age of the neuromas. The responses to capsaicin were similar to those seen with normal saphenous nerve endings, including bursting discharges and desensitization with repeated applications. The results are considered in the context of the requirements for reexpression of normal sensory capacities on regenerating sensory nerve endings.

Ribosomal DNA is located and transcribed in the dense fibrillar component of human Sertoli cell nucleoli

The distribution of rDNA and the uptake of tritiated uridine was investigated in nucleoli of human Sertoli cells. The nucleolar components in these cells are spatially arranged in a highly ordered and invariable way and can be recognized in both light and electron microscopy. The pattern of distribution of rDNA and the pattern of uridine uptake in these nucleoli correspond to the distribution of the dense fibrillar component but cannot be correlated to the shape and size of the fibrillar centers in these cells. It therefore can be concluded that the dense fibrillar component, and not the fibrillar centers, is the site of rDNA location and transcription in nucleoli of human Sertoli cells.

[Malignant diseases of the inner nose--epidemiology and occupational medicine aspects]

Squamous cell carcinomas are the most frequent malignancies of the inner nose, followed by adenocarcinomas, adenoid cystic carcinomas, and other malignant neoplasms. Carcinomas of the nose can be recognized as occupational diseases if there has been a professional exposition to ionizing rays, certain arsenic compounds, hexavalent chrome compounds, nickel, oak or beech wood dust. The sources of danger relevant in industrial medicine are indicated. At present, adenocarcinomas induced by dust of wood are of special significance: 16 out of 22 carcinomas of the nose recognized as occupational diseases between 1978 and 1986 are due to oak and beech wood dust.

[Effect and side effects of oral morphine, lormetazepam and placebos as premedication]

In 60 patients undergoing a curettage in thiopentone induced inhalation anaesthesia with enflurane and N2O/O2 = 2:1, the effects of oral premedication (2 h before anaesthesia) with 30 mg morphine (MST 30) (n = 21), 1 mg lormetazepam (Noctamid) (n = 19) and placebo (n = 21) on psychological (anxiety, depression and asthenia), physiological (blood pressure, heart and respiratory rate) and pain parameters (visual analogue scale, analgesic consumption) were investigated. The study design was single blind, randomized. Before premedication the three groups did not differ in one parameter and so were comparable. MST 30 had a significantly better anxiolytic, Lormetazepam a significantly better antidepressive effect than the compared substance. There were no differences in blood pressure and heart rate. In contrast to lormetazepam and placebo after MST 30 there was no increase in the respiratory rate which can be explained by the anxiolytic stress reducing effect. There was no difference in peri- and intraoperative pain parameters, probably due to the type of surgery. Nausea and vomiting occurred more frequently after MST 30, but there was no significance. A higher rate was probably prevented by the application of transdermal scopolamine the day before surgery. The indication of analgesics (opiates) for premedication is discussed taking the controversy into account. The results of this study show that oral morphine (MST 30) has an anxiolytic effect, one of the most important effects a premedication should have. Further studies should investigate in which types of surgery the analgesic effect of MST 30 is peri- and intraoperatively relevant, so that advantages compared to e.g. Flunitrazepam, Midazolam or Lormetazepam in a higher dosage could be expected.

[Midazolam and pethidine/promethazine for intramuscular premedication]

The main reason for premedication is the reduction of preoperative stress. Despite the proven fact that benzodiazepines best reduce preoperative stress, combinations of opioids and neuroleptic drugs are preferred for premedication by many on reviewing the journal Der Anaesthesist. This double-blind study was performed to investigate midazolam and meperidine/promethazine for intramuscular premedication. Method. 60 patients undergoing minor gynecological surgery were randomly assigned to receive either 5-7.5 mg midazolam or 50-75 mg meperidine and 25-50 mg promethazine intramuscularly 30-90 min before surgery. Anxiety, depression, and asthenia were assessed by the patient before and after premedication but before induction of anesthesia using visual analogue scales and a nominal scale. Sedation was assessed by an observer. Heart rate and blood pressure were the physiological stress parameters. Parameters of acceptance and side effects were registered perioperatively. Results. Midazolam had a significantly better anxiolytic and antidepressive effect. There were no differences in the other parameters except for adverse effects. Meperidine/promethazine produced significantly more side-effects than midazolam. The parameters of acceptance assessed the day after surgery were comparable. Conclusions. We conclude from these results that anesthesiologists still premedicate with meperidine/promethazine because the patients accept this premedication very well when asked the day after surgery. Nevertheless, premedication with midazolam provides significantly better anxiolytic and antidepressive effects with significantly less side-effects. Therefore, midazolam should be preferred to meperidine/promethazine for intramuscular premedication.