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J Frey

Publications and source records attributed to J Frey.

At least 163 records · Page 9Linked to original sources
PubMed1994

Association of the CAMP phenomenon in Actinobacillus pleuropneumoniae with the RTX toxins ApxI, ApxII and ApxIII.

A non-hemolytic mutant of Actinobacillus pleuropneumoniae serotype 5 has a deletion spanning the entire apxI operon. Therefore it does not produce ApxI and is unable to secrete ApxII. This mutant also has lost the co-hemolytic CAMP effect which is characteristic of the species A. pleuropneumoniae. The CAMP effect is restored when the mutant is complemented in trans by the apxIBD genes cloned in a broad host range vector, thus permitting secretion of ApxII, or when the entire apxI operon is cloned in the mutant, thus restoring the original toxin phenotype ApxI+ ApxII+. When the toxins ApxI, ApxII or ApxIII individually are expressed and secreted from E. coli harboring recombinant plasmids containing the genes apxICA and apxIBD or apxIICA and apxIBD or apxIIICABD, respectively, the distinct CAMP phenomenon is produced by the recombinant strains. The CAMP phenomenon is strongest by the recombinant E. coli strain expressing the non-hemolytic ApxIII, somewhat less when ApxI is expressed, and weak when ApxII is expressed. In A. pleuropneumoniae the CAMP phenomenon is also strongest in those serotypes which express ApxIII. The CAMP phenomenon of A. pleuropneumoniae is assumed to be directly caused by any of the RTX-toxins ApxI, ApxII or ApxIII. A previously reported gene from A. pleuropneumoniae, named cfp or hlyX, which provides E. coli strains with a hemolytic character and a CAMP phenomenon, shows high similarity to the E. coli global regulation gene fnr, and which is able to complement a delta fnr mutant.(ABSTRACT TRUNCATED AT 250 WORDS)

Actinobacillus pleuropneumoniae↗
PubMed1994

Sequence analysis and transcription of the apxI operon (hemolysin I) from Actinobacillus pleuropneumoniae.

The DNA sequence of the entire apxI operon from Actinobacillus pleuropneumoniae serotype 1 reference strain 4074 has been determined. This 8292-bp fragment of the chromosomal DNA contains four open reading frames (ORFs) of the strongly hemolytic ApxI toxin. These ORFs correspond to the genes apxIC, apxIA, apxIB and apxID, encoding the activator, the structural toxin protein and the two secretion proteins, respectively. Each of the four ORFs is preceded by a consensus sequence for a putative ribosome-binding site (RBS). The region upstream from apxIC contains several sites that could act as promoters. The transcription start point (tsp) of the apxI operon in A. pleuropneumoniae has been determined by primer extension analysis and was found to be located 133-bp upstream from the translation start codon. The tsp is preceded by sequences matching the -10 and -35 consensus sequence of promoters from Escherichia coli. This is the first promoter identified in A. pleuropneumoniae. The same tsp was used when the expression of apxI was induced by a high concentration of free Ca2+ in the growth medium, as well as when the expression of apxI was not induced by growing the cells in medium depleted of free Ca2+ ions. However, the signal strength of the primer extension was approximately tenfold stronger in Ca(2+)-grown cells. The leader sequence of the transcript is unusually long and very A+U rich (75% A+U).

Actinobacillus pleuropneumoniae↗
PubMed1994

Immune response against the L-lactate dehydrogenase of Mycoplasma hyopneumoniae in enzootic pneumonia of swine.

The L-lactate dehydrogenase (LDH) of Mycoplasma hyopneumoniae, formerly named protein P36, belongs to the predominant immunogenic proteins in pigs which were naturally or experimentally infected with M. hyopneumoniae. The antigenic reaction against M. hyopneumoniae LDH has been shown to be species specific. Recombinant M. hyopneumoniae LDH, which was genetically engineered to contain six histidine residues at its C-terminal end, was expressed in E. coli and purified to a high degree using Ni-chelate affinity chromatography. The genetically engineered LDH still showed the same biochemical activity and immunological specificity as the wild-type LDH and was used as an antigen for a M. hyopneumoniae LDH ELISA. Using this assay, we showed that pigs experimentally infected with M. hyopneumoniae raised antibodies against LDH in two steps. An early, relatively weak anti-LDH response was detected between 5 to 10 weeks post-infection when clinical signs and lung lesions occur. This first minor raise of anti-LDH antibodies occurred simultaneously with the strong appearance of antibodies against an antigen consisting of membrane proteins of M. hyopneumoniae prepared with Tween 20 extraction. A second, strong raise in anti-LDH antibodies was observed from the twelfth week after infection, at a time when the disease signs and the infectious agent disappeared. The high anti-LDH titer persisted until 21 weeks post-infection, in contrast to the antibody titer against the membrane proteins which started to decrease after its peak at 12 weeks post-infection. A LDH-ELISA may also be useful for detecting past infections.

Amino Acid Sequence↗
PubMed1994

Repetitive plasmid sequences generate DNA fingerprinting patterns in mammals.

Bacterial plasmids with stringently regulated copy numbers have directly repeated DNA sequences, termed iterons, in the vicinity of their replication origins. These sequences bind a specific protein exerting a key role in the initiation of plasmid replication. Plasmids P1, pSC101 and RFS1010 have different iteron sequences and belong to three different incompatibility groups. Used as DNA probes each of these plasmids generates specific patterns in mammals similar to those obtained by the DNA fingerprinting technique. The iteron-containing regions were identified as the part of the plasmids responsible for those patterns by using polymerase chain reaction (PCR) amplified DNA segments that contained the iteron regions as probes.

Animals↗
PubMed1994

RTX toxin genotypes and phenotypes in Actinobacillus pleuropneumoniae field strains.

Actinobacillus pleuropneumoniae serotype reference strains and 204 A. pleuropneumoniae field strains representing all 12 serotypes and both biovars 1 and 2, obtained from laboratories from various countries worldwide, were analyzed for the presence of the toxin genes apxIC, apxIA, apxIB, apxID, apxIIC, apxIIA, apxIIIC, apxIIIA, apxIIIB, and apxIIID by DNA-DNA hybridization with specific gene probes. Expression of the toxins ApxI, ApxII, and ApxIII was assessed by immunoblot analysis with monoclonal antibodies. The results show that the patterns of apx genes and those of the expressed Apx toxins in biovar 1 field strains are the same as those of the genes and toxins of corresponding serotype reference strain. We found only three strains which had certain apx genes missing compared with the genes in their serotype reference strains. Analysis of the expression of the three toxins showed that nearly all strains expressed their apx genes and produced the same Apx toxins as their serotype reference strain. We found only one strain that did not produce ApxI, although it contained the apxICABD genes, and one strain which did not express ApxII but which contained apxIICA. Several field strains which initially showed that their serotype did not correspond to the apx gene profile of the reference strain and which had an unexpected virulence for the given serotype revealed that their initial serotyping was erroneous. We show that the apx gene profiles are inherent to a given serotype. The method cannot differentiate between all 12 serotypes. However, it allowed us to distinguish five groups of toxin gene patterns which showed pathological, toxicological, and epidemiological significance. None of the biovar 2 strains contained apxIII genes. The apxI and apxII genes in the biovar 2 strains, however, were the same as those found in the serotype reference strains of biovar 1.

Actinobacillus pleuropneumoniae↗
PubMed1994

Baseline silent cerebral infarction in the Asymptomatic Carotid Atherosclerosis Study.

BACKGROUND AND PURPOSE: In a group of patients with high-grade asymptomatic carotid artery stenosis, we prospectively determined the prevalence and radiological characteristics of clinically asymptomatic brain infarction evident on computed tomography. Risk factors and extent of carotid disease were also determined. METHODS: Patients randomized into the Asymptomatic Carotid Atherosclerosis Study (ACAS) underwent a neurological history, a detailed stroke/transient ischemic attack questionnaire, and a detailed neurological examination. Computed tomography scans were examined by standardized criteria developed as part of a quality-control program supervised by a neuroradiologist. The presence, location, and size of all cerebral infarctions evident by computed tomography were determined. RESULTS: Among 1132 patients, 848 had no history of stroke or transient ischemic attack. One hundred twenty-six patients (15%) had a silent infarct; 95 (11%) had one, 24 (3%) had two, and 7 (1%) had three or more infarcts. The infarct size was small and deep for 117 patients (72%), less than one-half lobe for 45 (28%), and one-half to less than one lobe for 1 (0.5%). The silent infarcts were evenly distributed ipsilaterally and contralaterally to the study artery but were significantly more frequent in the right hemisphere (P < .05). Factors associated with silent infarction were abnormal gait (P < .001), abnormal deep tendon reflexes or plantar responses (P = .038), but not degree of carotid stenosis. Silent infarction was less frequent among this totally asymptomatic cohort (15%) compared with those with transient ischemic attacks (34/139, 25%; P < .001). CONCLUSIONS: Silent infarction in the setting of asymptomatic carotid stenosis is not uncommon, but silent infarctions are rarely sizable. The clinical significance of silent cerebral infarction in patients with asymptomatic carotid artery stenosis has yet to be established.

Adult↗
PubMed1994

Fluoxetine suppresses human cataplexy: a pilot study.

We evaluated fluoxetine in six patients with poorly controlled cataplexy by beginning patients on a single 20 mg dose without any change in their current medications. Once benefit occurred, we discontinued or reduced other anticataplectic medication. Reduction in the number of cataplectic episodes per week after 20 weeks of treatment constituted the basis for efficacy determination. Patients experienced a mean reduction of 92% (a mean drop in frequency of 21.7 to 1.7 episodes per week). Although fluoxetine-induced headache occurred in one patient, the other five reported no side effects at the doses used. The results of this pilot study demonstrate that fluoxetine safely and effectively suppresses cataplexy and reduces the need for other, less desirable, anticataplectic agents.

Aged↗
PubMed1994

Biological functions of human Fc gamma RIIa/Fc gamma RIIc in B cells.

The human immunoglobulin receptor IIa (FcRIIa) was transfected into the FcR- mouse B cell line IIA1.6 to study its role in mediating endocytosis of human IgG complexes as well as its possible function in inhibiting the attenuated increased calcium level in B cells after antigen receptor cross-linking. Using FcRIIa mutants with truncated cytoplasmic domains we show that the region within the cytoplasmic region necessary for endocytosis differs from that necessary for the abrogation of the elevated calcium level in B cells induced after antigen receptor cross-linking. Deletion of 14 amino acids at the carboxy terminus led to a slow internalization of FcRIIa bound human IgG, whereas the mutant lacking 30 amino acids completely failed to mediate IgG uptake. The mutant lacking 14 amino acids at the carboxy terminus is not tyrosine phosphorylated in the course of receptor-mediated IgG uptake. This suggests that phosphorylation of FcRIIa is not necessary to mediate this function. FcRIIa cross-linking leads to a rapid transient rise in the intracellular calcium concentration due to calcium release from intracellular stores. Using the FcRIIa mutants we could further show that the signal delivered by FcRIIa is strongly dependent on the last 14 amino acids of the cytoplasmic tail. Analyses of the tyrosine phosphorylation of FcRIIa revealed that the calcium release mediated by FcRIIa cross-linking is dependent on tyrosine phosphorylation. In contrast, inhibition of the antigen receptor (sIgG) induced rise in intracellular calcium concentration by FcRIIa-sIgG co-cross-linking was not impaired when 30 amino acids were deleted at the carboxy terminus. FcRIIa wild type was rapidly phosphorylated when co-cross-linked with sIgG, but phosphorylation is not a prerequisite to inhibit calcium influx induced by sIgG cross-linking. These results show that distinct regions within the cytoplasmic tail of FcRIIa are necessary for the various signals transmitted to the cell.

Amino Acid Sequence↗
PubMed1993

[The place of percutaneous transluminal angioplasty in the management of obliterative vascular diseases of the lower extremities. Femoro-popliteal arterial angioplasty].

Authors treated 331 patients having symptoms of femoropopliteal stenoses or occlusions with transluminal angioplasty from 1983. They performed 186 dilatations and 189 recanalizations. Procedures were preceded by medicinal preparation. The primary technical success rate was 94.6% after dilatation, and 79.9% after recanalisation. In case of stenosis the success rate did not show significant connection with the length of the dilated segment but in case of occlusion longer than 6 cm the success rate decreased. After procedure 87.2% of the patients became asymptomatic, or improved. 21 (5.6%) complications (7 inguinal hematomas, 6 emboles, 6 thromboses, one perforation of arterial wall) occurred and twelve of them required surgical intervention. One patient died after angioplasty due to cardiac failure. Authors are of the opinion that femoropopliteal occlusions and stenoses shorter than 6 cm should be treated by angioplasty. They suggest making balloon catheter dilatation for multiple stenoses even they are longer than 6 cm.

Aged↗
PubMed1993

Analysis of hemolysin operons in Actinobacillus pleuropneumoniae.

Among the twelve different serotypes of Actinobacillus pleuropneumoniae, the causative agent of swine pleuropneumonia, a strongly active hemolysin I (HlyI) is produced by serotypes which are particularly virulent, and less active hemolysin II (HlyII) is produced by all serotypes except type 10. In the serotypes 1, 5a, 5b, 9, 10 and 11, which produce HlyI, the hemolysin (hly) operon consists of a structural hlyIA gene, encoding pre-HlyI, an activator gene, hlyIC, necessary for the activation of pre-Hly to active Hly, and two genes, hlyIB and hlyID, involved in Hly secretion. These genes are clustered in the order, hlyICABD. This is characteristic to RTX toxin (repeats in the structural toxin) operons. The HlyII operons in all serotypes producing HlyII consist only of the pre-HlyII-encoding gene, appA, and its activator gene, appC. The serotypes, which produce HlyII, but not HlyI, contain a truncated HlyI operon, with the promoter, hlyIB and hlyID, and a small segment of the C terminus of hlyIA. This partial HlyI operon might have been formed by deletion of hlyIC and most of hlyIA. In serotype 3, which produces HlyII, but no HlyI, and which releases only minute amounts of this Hly into the growth medium, none of the hlyI genes and consequently no Hly secretion genes were found. The above results postulate that HlyII is secreted via the products of hlyIB and hlyID, and explain the low amount of HlyII secreted by serotype 3. Cloning and analysis of the structural genes encoding pre-HlyI and pre-HlyII among the different serotypes revealed differences in the hlyIA genes which are highly similar in the serologically related serotypes 1, 9 and 11, and differ from the serotypes, 5a, 5b and 10. The hlyIIA genes, in contrast, seem to be conserved in all serotypes.

Actinobacillus pleuropneumoniae↗
PubMed1993

A cyclophilin-related protein involved in the function of natural killer cells.

Natural killer cells are non-major histocompatibility complex-restricted large granular lymphocytes that can recognize and destroy tumor cells without prior stimulation. A 150-kDa molecule on the surface of human natural killer cells was identified as a component of a putative tumor-recognition complex. We report here the isolation of cDNAs coding for the 150-kDa tumor-recognition molecule from human and mouse cDNA libraries. The amino terminus of the predicted protein contains a large hydrophobic region followed by a domain that is highly homologous to cyclophilin/peptidylprolyl cis-trans isomerase. The remainder of the protein is extremely hydrophilic and contains three homologous positively charged clusters. There are also three regions that contain extensive arginine- and serine-rich repeats. Comparison of the human and mouse predicted amino acid sequences revealed > 80% homology.

Amino Acid Isomerases↗
PubMed1993

Iterons of stringently controlled plasmids and DNA fingerprinting.

DNA probes which detect polymorphic, repetitive sequences in a variety of genomes have been developed using different approaches. Naturally occurring plasmids, with repeated units termed iterons near or within their origins (ori) or replication, could be of interest for the development of probes, possibly even revealing novel minisatellite families in mammals involved in replicational processes. We used the plasmids P1, pSC101 and RSF1010 or their PCR amplified ori regions as probes in Southern blot hybridisations with mammalian DNA. At low stringency they generated reproducible fingerprint-like patterns. A bovine genomic library was screened at the same stringency with the PCR-amplified ori region of P1 containing the five times repeated core sequence 5'-ATGTGTGNTGNNGGG-3' to generate a probe for cattle DNA with higher specificity.

Animals↗
PubMed1993

The disulfide bridges of the immunoglobulin-like domains of Fc gamma RIIIB are essential for efficient expression and biological activity.

The immunoglobulin G receptor Fc gamma RIIIB belongs to the immunoglobulin superfamily as two extracellular domains show homology to the immunoglobulin domains. Since some residues in these domains, such as the two cysteines, are supposed to form an intrachain disulfide bridge are so commonly conserved, they may be of importance for correct folding. Site-directed mutagenesis and expression in BHK21 confirmed this supposition for the Fc gamma RIIIB. Replacing both cysteines in the first and/or second domain by serines reduced the surface expression level by 50%, whereas the ligand binding capability was 20-30% of that seen in cells expressing the wild-type receptor. Replacing one of the four cysteines resulted in the loss of surface expression. Exchanging the conserved tryptophan in the first domain by phenylalanine only slightly affected the ligand binding (25%), whereas the surface expression remained unchanged.

Animals↗
PubMed1993

DNA sequence determination and biochemical analysis of the immunogenic protein P36, the lactate dehydrogenase (LDH) of Mycoplasma hyopneumoniae.

The DNA sequence of the gene encoding the early and specific immunogenic protein P36 of Mycoplasma hyopneumoniae has been determined. Comparison of the DNA sequence and the deduced amino acid sequence of P36 with known genes and proteins in data banks indicated that P36 is a L-lactate dehydrogenase (LDH) (EC 1.1.1.27). Biochemical analysis of protein P36 expressed from the cloned gene in Escherichia coli confirmed that P36 has L-lactate dehydrogenase activity. Protein P36 of M. hyopneumoniae therefore is termed LDH and its gene ldh. M. hyopneumoniae LDH was shown to contain the typical domains of LDH of other bacterial species. Immunologically however, we have shown that polyclonal antibodies against M. hyopneumoniae LDH do not cross-react with related LDH and show high specificity for M. hyopneumoniae. The ldh gene is preceded by several typical -10 sequences found in promoters of prokaryotes, but lacks the -35 sequence. Sequences rich in A+T, however, precede the -10 boxes, suggesting that factors involved in transcription initiation and their regulation may be different in M. hyopneumoniae compared to other bacterial species, but the putative ribosome binding site seems to be conserved.

Amino Acid Sequence↗
PubMed1993

Actinobacillus pleuropneumoniae RTX-toxins: uniform designation of haemolysins, cytolysins, pleurotoxin and their genes.

The three different pore-forming RTX-toxins of Actinobacillus pleuropneumoniae are reviewed, and new and uniform designations for these toxins and their genes are proposed. The designation ApxI (for Actinobacillus pleuropneumoniae RTX-toxin I) is proposed for the RTX-toxin produced by the reference strains for serotypes 1, 5a, 5b, 9, 10 and 11, which was previously named haemolysin I (HlyI) or cytolysin I (ClyI). This protein is strongly haemolytic and shows strong cytotoxic activity towards pig alveolar macrophages and neutrophils; it has an apparent molecular mass in the range 105 to 110 kDa. The genes of the apxI operon will have the designations apxIC, apxIA, apxIB, and apxID for the activator, the structural gene and the two secretion genes respectively. The designation ApxII is proposed for the RTX-toxin which is produced by all serotype reference strains except serotype 10 and which was previously named App, HlyII, ClyII or Cyt. This protein is weakly haemolytic and moderately cytotoxic and has an apparent molecular mass between 103 and 105 kDa. The genes of the apxII operon will have the designations apxIIC for the activator gene and apxIIA for the structural toxin gene. In the apxII operon, no genes for secretion proteins have been found. Secretion of ApxII seems to occur via the products of the secretion genes apxIB and apxID of the apxI operon. The designation ApxIII is proposed for the nonhaemolytic RTX-toxin of the reference strains for serotypes 2, 3, 4, 6 and 8, which was previously named cytolysin III (ClyIII), pleurotoxin (Ptx), or macrophage toxin (Mat).(ABSTRACT TRUNCATED AT 250 WORDS)

Actinobacillus pleuropneumoniae↗
PubMed1993

Family transitions and developmental processes in panic-disordered patients.

Although there is increasing evidence for a familial role in panic disorder, little research exists on the family interaction patterns and relational stressors that may contribute to this disorder. Using DSM-III-R criteria, 52 families were classified into Panic Disorder, Major Depressive Disorder, and Nonclinical Control groups. A semi-structured interview and self-report measures were then used to examine family processes. MANOVA results were highly significant, suggesting that, compared to depressed and nonclinical control families, panic-disordered families had unresolved life-cycle issues, were enmeshed, used triangulation, and failed to resolve conflicts. These findings suggest that dysfunctional family processes may be involved in the expression and maintenance of panic disorder.

Adaptation, Psychological↗