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Biomedical subjects

A Mayr

Publications and source records attributed to A Mayr.

At least 55 records · Page 3Linked to original sources
PubMed1997

Gas vesicle formation in halophilic Archaea.

Gas vesicles are intracellular, microbial flotation devices that consist of mainly one protein, GvpA. The formation of halobacterial gas vesicles occurs along a complex pathway involving 14 different gvp genes that are clustered in a genomic region termed the "vac region". Various vac regions found in Halobacterium salinarum (p-vac and c-vac), Haloferax mediterranei (mc-vac), and Natronobacterium vacuolatum (nv-vac) have been investigated. Except for the latter vac region, the arrangement of the gvp genes is identical. Single gvp genes have been mutated to study the effect on gas vesicle synthesis in transformants and to determine their possible function. Each vac region exhibits a characteristic transcription pattern, and regulatory steps have been observed at the DNA, RNA, and protein level, indicating a complex regulatory network acting during gas vesicle gene expression.

Archaeal Proteins↗
PubMed1997

The characterization of the nv-gvpACNOFGH gene cluster involved in gas vesicle formation in Natronobacterium vacuolatum.

The haloalkaliphilic archaeon Natronobacterium vacuolatum forms cylinder-shaped gas vesicles throughout the growth cycle when grown in media containing 15-25% NaCl. Cells cultivated in media containing 13% NaCl are, however, gas-vesicle-free. The major gas vesicle structural protein, nv-GvpA, was detected by an antiserum raised against the gas vesicles of Haloferax mediterranei; the antiserum reacted with an 8.3-kDa protein in samples containing cell extracts or purified gas vesicles of N. vacuolatum. The gene encoding nv-GvpA was isolated together with six additional gvp genes; these genes are arranged consecutively in a cluster as nv-gvpACNOFGH and are cotranscribed. Transcript analysis by primer extension revealed only one start site three nucleotides upstream of the nv-gvpA reading frame. This arrangement of gvp genes differs from that of the gas-vesicle-encoding genes in Halobacterium salinarium and Hf. mediterranei. The comparison of the deduced Gvp protein sequences indicated similarities with the respective halobacterial Gvp proteins, with GvpA exhibiting the highest degree of conservation (97-100%). The second gas vesicle structural protein, nv-GvpC, was 150-250 amino acids longer than all other halobacterial GvpC proteins and was much less conserved (48-73%). The expression of the nv-gvp genes was monitored in N. vacuolatum cells cultivated in 20 or 13% salt media. Northern and Western analyses showed that despite the lack of gas vesicles in cells grown in 13% salt medium, the gvpACNOFGH gene cluster was transcribed and GvpA protein was synthesized, suggesting that the absence of gas vesicles is not due to a lack of transcription.

Amino Acid Sequence↗
PubMed1997

Poxvirus preparation CONPIND initiates production of the major inflammatory mediators IL-1 alpha and TNF-alpha in human whole blood and in blood mononuclear cell cultures.

The poxvirus preparation CONPIND initiated the production of the two major inflammatory mediators interleukin-1 alpha (IL-1 alpha) and tumour necrosis factor-alpha (TNF-alpha) in whole blood and in blood mononuclear cell cultures of man at 37 degrees C within 12-48 h. The release of the cytokines followed a dose-efficacy curve. High levels of IL1-alpha (up to 810 pg/ml) and TNF-alpha (up to 533 pg/ml) were determined by sandwich enzyme-linked immunosorbent assay.

Adjuvants, Immunologic↗
PubMed1997

[Comparative investigations of practice-oriented methods for the detection of viruses in food with Aujeszky infection in swine as an example].

In order to detect contamination in foodstuffs originating from animals, three different diagnostic methods were tested in comparison: cultivation in permissive cell cultures, microparticle antigen capture system per FACS (MAS) and polymerase chain reaction (PCR). Assessment implied relevance for health, sensitivity and specificity. Aujeszky infection in swine served as a model. The blood and organs of healthy, but persistently infected as well as specifically diseased animals were examined. In addition, artificially Aujeszky-contaminated milk, black pudding and minced meat were included in the comparison of methods. Basically, all three methods of detecting contamination in raw foodstuffs originating from animals were useful. The virus detection in cell cultures as well as the efficacy of MAS were inhibited by meat products according to their preparation (e.g., virus protein denaturation). PCR turned out to be the only reliable method to confirm the contamination in foodstuffs. Using PCR, viral contamination in foodstuffs originating from healthy but persistently infected animals could be detected. Each of the three virus detection systems has various advantages and disadvantages. They are listed and discussed in detail. With regard to the relevance of health, virus detection in raw meat via cell culture remains the preferred method. Besides the detection of an individual virus, routine examinations of foodstuffs for unknown zoonotic virus contamination, sets based on permissive cell cultures, primer sets for the PCR as well as sets based on various monoclonal antibodies for MAS have to be developed and made available at the diagnostic laboratories.

Animals↗
PubMed1996

A monoclonal blocking-ELISA for detection of orthopoxvirus antibodies in feline sera.

A double sandwich blocking-ELISA using a genus-specific neutralizing monoclonal antibody (MAb) against the vaccinia virus 32 kD adsorption protein (D8L open reading frame: ORF) was developed to detect orthopoxvirus (OPV) antibodies in sera. A collection of 2173 feline serum samples was examined in an epidemiological study. The blocking-ELISA revealed 44 (2%) sera with positive titres of 1:2-1:256. ELISA results were confirmed by the plaque-reduction test. A close correlation between titres of both assays could be observed (r = 0.986). In general, the sensitivity of the blocking ELISA was two to four times higher. Neutralizing OPV-antibodies were found in nine sera with ELISA-titres > 1:4. Antibody specificity to OPV was also demonstrated by Western blotting analysis with selected feline sera. The epidemiographical distribution of the ELISA-positive sera and case histories of 37 seropositive cats available from the referring veterinarians are demonstrated. The blocking-ELISA enables a rapid serological diagnosis and can be used in veterinary and human medicine. It allows OPV-antibody screening in human and other animal species.

Animals↗
PubMed1996

Immunoreactive cytokines within primates.

Peripheral blood mononuclear cells of primates (man, orang utan, gorilla, baboon), rodents (mouse, rat), carnivores (cat, dog), artiodactyls (cattle, goat, pig) and perissodactyls (horse) were isolated and stimulated with mitogens (5 micrograms/ml LPS, 5 micrograms/ml PHA) at 37 degrees C. Cytokines immunoreactive to monoclonal antibodies (mAb) directed to human cytokines (TNF-alpha, IL-1 alpha, IL-2, IL-6, IFN-gamma) could be detected by enzyme-linked immunosorbent assay (ELISA) in the case of primates only. The mAb used did not recognize cytokines of the other mammalian species investigated. The results demonstrate the close relationship within the primates from the immunophysiological point of view.

Animals↗
PubMed1995

[Determination of Escherichia coli Shiga-like toxins by means of the MTT bioassay].

Tissue culture cells' metabolism and viability are measured by the mitochondrial reduction rate of a yellow tetrazolium salt (MTT) to blue formazan crystals in the MTT-bioassay. Thus the MTT-bioassay is a standardizable and reproducible bioassay for measuring cytotoxicity or cytostimulation. It is shown that the MTT-bioassay is also very suitable for determining bacterial cytotoxins using Escherichia coli's Shiga-like toxins as example. 177 strains of E. coli, isolated from carcasses and organs of cattle, are classified biochemically and tested for cytotoxin production by means of the MTT-bioassay. One of these strains is recognized as producer of Shiga-like toxin 2. 4 Enterohemolysin-producing strains of E. coli are cultivated from a feces sample of a diarrhoeic nubian ibex and identified as Shiga-like toxin 1 producers by help of the MTT-bioassay.

Animals↗
PubMed1995

Mallory-Weiss syndrome in a patient with hemophilia A and chronic liver disease.

Eighty percent of hemophiliacs exposed to plasma products are seropositive to hepatitis B and an even higher percentage are seropositive to hepatitis C. Post-transfusion hepatitis is followed by cirrhosis in up to 25% of the cases. In the wake of portal hypertension, the development of oesophageal varices entails the risk of life-threatening hemorrhage. We report on a patient with moderate hemophilia A (factor VIII:C 4-11%) who suffered from massive hematemesis, melaena and evolving shock after excessive alcohol ingestion. The diagnosis of Mallory-Weiss syndrome and the differential diagnosis of bleeding oesophageal varices as well as prognostic consequences are discussed.

Adult↗
PubMed1995

[Present state of preclinical research on the efficacy and safety of para immunity inducers from poxviruses. A study of the literature].

The investigations on the "systemic level" after parenteral application of pox-inducers to man and animal have proved the preparations to be harmless and surprisingly effective with regard to certain indications. The clinical data correlate to laboratory parameters to serve as proof for the efficacy. The challenge models (VSV, Aujeszky) verify a dosis-efficacy relationship. The evaluation of the efficacy of the pox-inducers in isolated blood- and liver-cells respectively cell cultures (cellular "in vitro" level) provide a unified picture: increase of the phagocytosis, of the NK-cells and the thymidinkinase activity in liver cells. The investigations on the "cytokine release" illustrate that pox-inducers promote the release respectively the production of diverse cytokines important for the regulation of the immune system. This has been proved for interferon alpha and gamma, the interleukin 1, 2 and 12 as well as for CSF and TNF. To conclude, a regulative effect is ascribed to the poxvirus inducers in the network of paraspecific defence in regard to stimulating as well as inhibiting effects. The endogenous medication by way of pox-inducers (paramunization) is diametrically opposed to the exogenous application of cytokines.

Animals↗
PubMed1994

More than one component of the Newcastle disease virus particle is capable of interferon induction.

The interferon (IFN)-inducing capacities of intact NDV virions, beta-propiolactone-inactivated particles and several structural components were compared, using human PBML as the IFN producing cells. Intact and inactivated virions as well as the nucleocapsid fraction did not differ significantly in their IFN-inducing capacity. In contrast, genomic RNA as well as M protein fraction and envelopes induced IFN titres to a level of about 10% of those achieved with virions. NDV-induced IFN production could be blocked specifically by incubation with polyclonal anti-NDV-monoclonal antibodies (mAbs) and with two of three anti-HN-mAbs, but not with anti-NDV-mAbs directed against the F, M or NP protein. In addition, IFN induction by fixed MDBK cells, expressing NDV surface proteins after infection with NDV Ulster, was inhibited by one of two anti-F-mAbs. The results suggest that the induction of IFN synthesis in human PBML is a complex process involving not only the HN protein but also the uncleaved F protein precursor, a component of the M protein fraction and--once having entered the cell--the genomic RNA.

Animals↗
PubMed1994

Identification of CD34+ cord blood cells and their subpopulations in preterm and term neonates using three-color flow cytometry.

Three-color flow cytometry was used to identify CD34+ cord blood (CB) hematopoietic progenitors of preterm (n = 13) and term (n = 18) neonates. The frequency of CD34+ CB cells gated on the lymphocyte fraction in term neonates is about half the frequency of preterm neonates (mean 1.84 +/- 0.8 vs. 3.49 +/- 1.8, p < 0.005). The difference of absolute CD34+ cells between the 2 groups did not reach statistical significance (premature 169 +/- 161 vs. mature 108 +/- 62.6 x 10(6) cells/l). The proportion of myeloid lineage-committed CD34+ cells coexpressing the CD33 antigen in preterm neonates does not significantly differ from that found in term neonates. However, in preterm neonates a higher fraction of erythroid lineage-committed CD34+ cells coexpresses the CD71 antigen as compared with term neonates (mean 28.7 +/- 14.1 vs. 11.4 +/- 5.7, p < 0.001). The positive correlation between gestational age and the ratio of myeloid/erythroid lineage-specific progenitor cells (r = 0.61, n = 31, p < 0.0005) suggests gestational changes in lineage commitment of CD34+ cells.

Antigens, CD↗
PubMed1994

[Experiences with immunization against orthopox viruses of humans and animals using vaccine strain MVA].

Immunizations against orthopox virus infections require a replicating, but safe vaccinia virus. The strain MVA is well suited concerning this matter. Human beings and animals can be vaccinated without any risk. The virus propagated in cell culture is non-virulent and lost its contagiosity. Multiplication in vaccinated men and animals is limited and excretion does not happen. As known for other attenuated virus strains, there must be a minimal effective virus concentration in the vaccine, which is 10(7.5) TCID50 per ml for MVA. To achieve a solid basic immunity which endures for a minimal of one year, two parenteral applications of MVA at intervals of at least 3 weeks are necessary.

Animals↗