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Biomedical subjects

H Meyer

Publications and source records attributed to H Meyer.

At least 217 records · Page 12Linked to original sources
PubMed1996

[Immunization with potential Salmonella enteritidis mutants-- 2. Investigations on the attenuation and immunogenicity for mice and young hens].

Adenine-amino acid auxotrophic Salmonella Enteritidis double mutants were investigated for their in vivo stability, attenuation und immunogenicity using NMRI-mice and SPF-chicks. All mutants used were stable in vivo and attenuated. Two mutants were selected for immunization experiments in chickens according to their protective ability after a single intraperitoneal immunization in NMRI-mice using a homologous and heterologous challenge. After two oral immunizations and homologous oral challenge with the S. Enteritidis wild type strain 6403Nalr, a significant difference (p < 0.01) was demonstrated between the mean caecal bacterial counts of immunized and control chicks. Examination of liver samples revealed a significantly lower degree of colonization of internal organs (p < 0.01) in immunized birds. There was no evidence of cross protection against S. Typhimurium using S. Enteritidis mutants.

Animals↗
PubMed1996

Mousepox outbreak in a laboratory mouse colony.

Mousepox was diagnosed in and eradicated from a laboratory mouse colony at the Naval Medical Research Institute. The outbreak began with increased mortality in a single room; subsequently, small numbers of animals in separate cages in other rooms were involved. Signs of disease were often mild, and overall mortality was low; BALB/cByJ mice were more severely affected, and many of them died spontaneously. Conjunctivitis was the most common clinical sign of disease in addition to occasional small, crusty scabs on sparsely haired or hairless areas of skin. Necropsy findings included conjunctivitis, enlarged spleen, and pale liver. Hemorrhage into the pyloric region of the stomach and proximal portion of the small intestine was observed in experimentally infected animals. In immune competent and immune deficient mice, the most common histologic finding was multifocal to coalescing splenic necrosis; necrosis was seen less frequently in liver, lymph nodes, and Peyer's patches. Necrosis was rarely observed in ovary, vagina, uterus, colon, or lung. Splenic necrosis often involved over 50% of the examined tissue, including white and red pulp. Hepatic necrosis was evident as either large, well-demarcated areas of coagulative necrosis or as multiple, random, interlacing bands of necrosis. Intracytoplasmic eosinophilic inclusion bodies were seen in conjunctival mucosae and haired palpebra. Ectromelia virus was confirmed as the causative agent of the epizootic by electron microscopy, immunohistochemistry, animal inoculations, serologic testing, virus isolation, and polymerase chain reaction. Serologic testing was of little value in the initial stages of the outbreak, although 6 weeks later, orthopoxvirus-specific antibody was detected in colony mice by indirect fluorescent antibody and enzyme-linked immunosorbent assay procedures. The outbreak originated from injection of mice with a contaminated, commercially produced, pooled mouse serum. The most relevant concern may be the unknown location of the source of the virus and the presence of a reservoir for this virus within the United States.

Animals↗
PubMed1996

In vivo and in vitro characterization of two camelpoxvirus isolates with decreased virulence.

Two camelpoxvirus (CPV) strains isolated from camels with generalized skin-disease were serially passaged on Vero cells. Various phenotypic properties were investigated in vitro and in vivo and compared with those of the corresponding wildtype strains. In many aspects no differences were observed. However, in a mouse model both passaged strains proved to be highly attenuated. In addition, both strains failed to replicate in a cell line derived from camel skin cells. Comparison of physical maps established for enzymes HindIII and Xhol revealed deletions accounting for a total of 22 kbp in one attenuated strain. In the second strain only minor alterations were noted.

Animals↗
PubMed1996

[Immunization with potential Salmonella enteritidis mutants--1. Production and in vitro characterization].

Production and in vitro characterization of potential vaccine strains are the first steps leading to an efficient Salmonella Enteritidis oral live vaccine for homologous immunization of poultry. The paper presents the results of the production of adenine-amino acid auxotrophic mutants using N-methyl-N'-nitro-N-nitrosoguanidine mutagenesis. The mutant strains were characterized using the following properties: auxotrophy, stability of mutation, reversion rate, generation time, metabolic properties, serotype, motility, plasmid content, phage type, SDS-PAGE patterns, as well as cell culture adhesion and invasion. Ten S. Enteritidis double auxotrophic mutants were obtained which are stable auxotrophically and where the risk of reversion was minimal. All strains were found to be plasmid-free. 5 mutants were selected for further investigations concerning their attenuation and immunological value.

Animals↗
PubMed1996

[Inhibition phenomena between Salmonella strains--a new aspect of salmonella infection control in poultry].

Freshly hatched chickens show a very high susceptibility to Salmonella infections and control measures are therefore frequently focused on the period shortly after hatching. Experimental investigations using one strain against itself, differentiated by different antibiotic resistance markers, have shown that colonisation with Salmonella prevents the establishment of subsequently inoculated challenge organisms in the chicken gut. The inhibition effect lasts for several days and is detectable even when a challenge dose of 10(8) organisms is used. It is dependent of the breed of bird. Chickens colonised with Salmonella shed a subsequently inoculated challenge strain with significant lower numbers for several weeks than do non colonised control birds. The phenomenon is strain specific but not serovarspecific as has been shown in investigations using different strains of the same and other serovars for colonisation and challenge. The phenomenon shows a large variability between strains. Using other Enterobacteriaceae strains comparable inhibition against Salmonella was not observed. One important topic for further investigation is the capability of Salmonella live vaccines given orally to establish a protection effect, based on the inhibition phenomenon in the first few days of live, developing into a long-lasting immunity when birds reach immunological maturity.

Animals↗
PubMed1995

gp13 (EHV-gC): a complement receptor induced by equine herpesviruses.

Equine herpesviruses type 1 (EHV-1) and type 4 (EHV-4) induce a complement receptor protein on the surface of infected cells capable of binding to the third component of complement (C3). The protein mediating the binding to the C3 component of complement was identified as glycoprotein 13 (gp13, EHV-gC), as expression of the cloned viral gene under the control of a CMV promoter induced C3 binding activity at the transfected cell surface. Comparable to glycoprotein C (gC) from herpes simplex virus type 1 (HSV-1-gC), glycoprotein III from pseudorabiesvirus (gIII, PRV-gC) and bovine herpesvirus-1 (gIII, BHV-1-gC), gp13 derived from EHV-infected cell lysates bound to C3 fixed to solid phase, showing preferential binding to the appropriate host complement component. Similar to wild-type isolates, a highly attenuated vaccine EHV-1 strain also displayed complement receptor activity despite apparent differences of the gp13 gene in restriction enzyme digest pattern and reactivity with monoclonal antibodies. In addition, other structural proteins were altered in the vaccine strain as compared to wild-type strains, which might contribute to its attenuated phenotype. In contrast to the situation observed with HSV-1-gC, the interaction of gp13 (EHV-gC) with horse complement was not inhibited by polyanionic substances like heparin or dextran sulfate. These results suggest structural differences in the particular binding mechanism of the respective viral envelope proteins.

Animals↗
PubMed1995

A seroepidemiological survey for orthopox virus in the red fox (Vulpes vulpes).

703 blood samples from red foxes (Vulpes vulpes) were investigated to determine the prevalence of antibody against an orthopox virus (vaccinia virus strain Elstree). A blocking-ELISA based on a neutralizing monoclonal antibody was used. In this assay 46 sera (6.5%) were positive with titers of 1:2 to 1:16. ELISA-results were confirmed by the plaque reduction test with 44 of the 46 sera reacting positively. The specificity of antibodies in 21 selected sera was also demonstrated by Western blot analysis.

Animals↗
PubMed1995

Characterization of camelpoxvirus isolates from Africa and Asia.

Five orthopoxvirus isolates of camels from different geographic regions of Africa and Asia were analysed with respect to their biological and genomic attributes. The behaviour of the isolates in various cell cultures, the type of pock lesions on the chorioallantoic membrane of embryonated chicken eggs, and the respective ceiling temperatures were determined. Additionally, physical maps for restriction endonucleases HindIII and XhoI were established. The data obtained from biological assays and DNA analyses demonstrated minor differences between the five isolates. However, these findings confirm previous reports suggesting that orthopoxviruses of camels constitute a separate species within the genus Orthopoxvirus.

Africa↗
PubMed1995

Nuclear localization of the human cytomegalovirus tegument protein pp150 (ppUL32).

The human cytomegalovirus (HCMV) basic phosphoprotein pp150, encoded by the UL32 gene, together with the two other major phosphoproteins, pp65 (ppUL83) and pp71 (ppUL82) and several minor structural proteins, form the tegument around the viral nucleocapsid. Experiments were undertaken to locate the area of assembly of tegument proteins pp150 and pp65 and nucleocapsids in fibroblasts, in order to assess the functional role of these two structural proteins in HCMV morphogenesis. Whereas pp150 expression starts during the cytoplasmic maturation of HCMV, pp65 is expressed in the early and late phases of HCMV gene transcription. Western blot analysis of isolated cell fractions showed that pp150 is initially (48 h post-infection) localized in the nucleus, associated either with the nuclear membrane or with viral assembly regions, and later (72 h post-infection) in the cytoplasm. By indirect immunofluorescence, pp150 and pp65 could be detected in nuclear subcompartments and were strongly associated with the nuclear membrane. Using immunogold analysis by electron microscopy, pp65 was exclusively detected within the matrix of cytoplasmic and extracellular dense bodies and of dense body-like structures in the nucleoplasm. These were localized in close contact with hypertrophic nucleoli, in the proximity of developing nucleocapsids and in special patches at the inner nuclear membrane. Positive immunostaining of pp150 was observed at the surface of developing nucleocapsids concentrated within viral assembly regions in the nucleoplasm. Additionally, the tegument of cytoplasmic and extracellular virions was stained, whereas dense bodies or nuclear dense body-like structures did not react. Thus, the acquisition of the tegument protein pp150 seems to start in special nuclear subcompartments of the HCMV-infected fibroblasts.

Cell Fractionation↗
PubMed1995

Investigations on preileal digestion of starch from grain, potato and manioc in horses.

In this study preileal starch digestibility of starchy feeds (oats, corn, barley, potatoes, manioc) was determined in seven jejunofistulated horses. The grains were fed whole (oats, corn), rolled (oats, barley), crushed, ground and expanded (corn); the potatoes were fresh, the manioc rolled. Ground corn was also fed in combination with amylase. The feeds were fed partly isolated or in combination with alfalfa meal or hay (Table 1). At least four horses with a cannula in the terminal jejunum were used for each diet. Two meals per day were offered at 12 h intervals. The starch intake was mostly about 2 g/kg bw/meal, except one period with oats (3.9 g starch/kg bw) and with expanded corn (1.4 g/kg bw). Jejunal chyme was postprandially collected 11 times (from 1st to the 11th h after the morning meal for 15 min). Starch was determined polarimetrically. The preileal digestibility of starch was calculated by the marker method (chronic oxide 0.25% DM) and by estimating the total jejunoileal chyme flow during 12 h postprandially extrapolating the sample volume from the 15 min sampling periods. The results of both methods agreed quite well. Preileal digestibility of oat starch (80-90%) was (independent of doses or preparation or of the combination with hay, Table 4) significantly higher than that of whole or crushed corn (30%) or barley (26%). Grinding of corn significantly increased preileal digestibility to 51%, expanding to 90%. The addition of amylase improved digestion of ground corn by 10% (absolute). The preileal digestibility of potato or manioc was less than 10%. Individual factors in the horse (chewing intensity, amylase activity) had also considerable influence on preileal starch digestibility.

Animals↗
PubMed1995

Experimental oral infection of specific pathogen-free laying hens and cocks with Salmonella enteritidis strains.

A total of 105 specific pathogen-free (SPF) laying hens and eight cocks were orally infected with strains of Salmonella enteritidis. The organs of these animals were examined bacteriologically for up to 6 weeks post infectionem (p.i.). One-half of the eggs laid on a single day were examined 1 day after laying, and the other half 28 days after laying. The siderophore, ferrioxamine E, was added to the pre-enrichment medium. A high correlation was found to exist between colonization of the caecum by salmonellas and the level of contamination of the egg shell. No correlation was found between the contamination of the egg shell and that of the egg content. The strains used for infection were not recovered from any yolk out of a total of 938 eggs. S. enteritidis was isolated from the albumen in four cases (0.4%). Storage of the eggs for 28 days after laying resulted in a decrease in the frequency of salmonella detection on the egg shell and in the egg content. The strains used for infection could be isolated from various sections of the sexual organs for up to 2 weeks p.i. S. enteritidis was most frequently found in the ovary and rarely in the oviduct, but never in the pre-ovulatory mature follicles. In the groups that included salmonella-infected cocks, the salmonella detection frequency did not increase either for the egg content or for the organs of the laying hens. It seems that primary vertical transmission of salmonellas occurs, in rare cases, as a result of an infection of the albumen but not of the yolk.

Animals↗
PubMed1995

Infection model for hatching chicks infected with Salmonella enteritidis.

A total of six different strains of Salmonella enteritidis (phage type 4) were used for the artificial infection of the egg yolk and albumen of SPF hatching eggs. An artificial yolk infection with low infection doses of S. enteritidis resulted in a considerable multiplication of salmonellas in the egg after a short time and a rapid embryonic death. After inoculation of 10(3) cfu of different S. enteritidis strains into the albumen, living day-old chicks infected with salmonellas were hatched. This model corresponds to a primary vertical transmission of salmonellas and permits the investigation of problems concerning the pathogen/host relationship.

Animals↗