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Biomedical subjects

G L Murphy

Publications and source records attributed to G L Murphy.

At least 19 recordsLinked to original sources
PubMed1999

Identification of immunogenic, surface-exposed outer membrane proteins of Pasteurella haemolytica serotype 1.

Pasteurella haemolytica serotype 1 (S1) is the bacterium most frequently recovered from the lungs of cattle that have succumbed to shipping fever pneumonia. P. haemolytica outer membrane proteins (OMPs) are important immunogens in the development of resistance to pneumonic pasteurellosis. The purpose of this study was to identify the repertoire of immunogenic, surface-exposed P. haemolytica (S1) OMPs, that could be important in the development of protective immunity. We determined surface exposure of OMPs by (1) their susceptibility to protease treatment and (2) their ability to adsorb out antibodies from bovine immune sera. For a comprehensive identification of immunogenic, surface-exposed OMPs, we used bovine antisera from calves that were resistant to experimental P. haemolytica challenge after (1) natural exposure to P. haemolytica, (2) vaccination with live P. haemolytica, or (3) vaccination with P. haemolytica OMPs. We identified 21 immunogenic, surface-exposed P. haemolytica OMPs. Most were recognized by all three immune sera. However, some were recognized by one or two of the three antisera. Our analyses identified surface-exposed, immunogenic proteins that were not identified in previous studies.

Animals↗
PubMed1999

Food for thought: cross-classification and category organization in a complex real-world domain.

Seven studies examined how people represent, access, and make inferences about a rich real-world category domain, foods. The representation of the category was assessed by category generation, category ratings, and item sortings. The first results indicated that the high-level category of foods was organized simultaneously by taxonomic categories for the kind of food (e.g., vegetables, meats) and script categories for the situations in which foods are eaten (e.g., breakfast foods, snacks). Sortings were dominated by the taxonomic categories, but the script categories also had an influence. The access of the categories was examined both by a similarity rating task, with and without the category labels, and by a speeded priming experiment. In both studies, the script categories showed less access than the taxonomic categories, but more than novel ad hoc categories, suggesting some intermediate level of access. Two studies on induction found that both types of categories could be used to make a wide range of inferences about food properties, but that they were differentially useful for different kinds of inferences. The results give a detailed picture of the use of cross-classification in a complex domain, demonstrating that multiple categories and ways of categorizing can be used in a single domain at one time.

Cognition↗
PubMed1999

Molecular cloning of the Pasteurella haemolytica pomA gene and identification of bovine antibodies against PomA surface domains.

The gene (pomA) encoding PomA, an OmpA-like major outer membrane protein of the bovine respiratory pathogen Pasteurella haemolytica, was cloned, and its nucleotide sequence was determined. The deduced amino acid sequence of PomA has significant identity with the sequences of other OmpA family proteins. Absorption of three different bovine immune sera with whole P. haemolytica cells resulted in a reduction of bovine immunoglobulin G reactivity with recombinant PomA in Western immunoblots, suggesting the presence of antibodies against PomA surface domains.

Amino Acid Sequence↗
PubMed1999

What is learned in knowledge-related categories? Evidence from typicality and feature frequency judgments.

When a category's features are tied together by integrative knowledge, subjects learn the category faster than when the features are not directly related. What do subjects learn about the category in such circumstances? Some research has suggested that the subjects can use the knowledge itself in performing the category learning task and, thus, do not learn the details of the category's features. Two experiments investigated this hypothesis by collecting feature frequency estimates after category learning. The results showed that integrative knowledge about a category did not decrease subjects' sensitivity to feature frequency--if anything, knowledge improved it. A third experiment found that integrative knowledge did reduce sensitivity to feature frequency in typicality ratings. The results suggest that knowledge does not inhibit the learning of detailed category information, though it may replace its use in some tasks.

Adult↗
PubMed1999

Induction with cross-classified categories.

One of the main functions of categories is to allow inferences about new objects. However, most objects are cross-classified, and it is not known whether and how people combine information from these different categories in making inferences. In six experiments, food categories, which are strongly cross-classified (e.g., a bagel is both a bread and a breakfast food), were studied. For each food, the subjects were told fictitious facts (e.g., 75% of breads are subject to spoilage from Aspergillus molds) about two of the categories to which it belonged and then were asked to make an inference about the food (e.g., how likely is a bagel to be subject to spoilage from Aspergillus molds?). We found no more use of multiple categories in these cases of cross-classification than in ambiguous classification, in which it is uncertain to which category an item belongs. However, some procedural manipulations did markedly increase the use of both categories in inferences, primarily those that focused the subjects' attention on the critical feature in both categories.

Adolescent↗
PubMed1999

The acquisition of category structure in unsupervised learning.

Four experiments examined the extent to which prior knowledge influences the acquisition of category structure in unsupervised learning conditions. Prior knowledge is general knowledge about a broad domain that explains why an object has the features it does. Category structure refers to the statistical regularities of features within and across categories. Subjects viewed items and then divided them up into the categories that seemed most natural. Each item had one feature that was related to prior knowledge and five features that were not. The results showed that even this small amount of prior knowledge helped subjects to discover the category structure. In addition, prior knowledge enhanced the learning of many of the category's features, and not just the features that were directly relevant to the knowledge. The results suggest that prior knowledge may help to integrate the features of a category, thereby improving the acquisition of category structure.

Adult↗
PubMed1998

A molecular and serologic survey of Ehrlichia canis, E. chaffeensis, and E. ewingii in dogs and ticks from Oklahoma.

Polymerase chain reaction and Southern hybridization were used to survey for the presence of Ehrlichia canis, Ehrlichia chaffeensis, and Ehrlichia ewingii in blood samples of 65 dogs that harbored ticks from northcentral and northeastern Oklahoma. Dog blood samples were also examined for antibodies against E. canis and E. chaffeensis, using an immunofluorescent antibody test. Ten of 65 dogs (15.4%) examined were positive for Ehrlichia spp. by PCR. Four (6.2%) were positive for E. ewingii, 2 (3.1%) for E. canis, and 4 (6.2%) for E. chaffeensis. Seven dogs (10.8%) were seropositive for E. canis or E. chaffeensis. Ticks collected from PCR-positive dogs were examined by PCR for the presence of Ehrlichia DNA. Several groups of ticks were PCR-positive for E. ewingii or E. canis. E. canis was detected in Rhipicephalus sanguineus, which is considered the major vector for that organism. E. ewingii was detected in a larger variety of ticks, including the only known vector Amblyomma americanum, as well as in Dermacentor variabilis and R. sanguineus. Results suggest that Ehrlichia spp. which are canine and human pathogens circulate in dogs in Oklahoma and in several tick species that feed on dogs.

Animals↗
PubMed1998

Development of a non-radioactive DNA probe and in situ hybridization for detection of Anaplasma marginale in ticks and cattle.

A non-radioactive DNA probe was developed for detection of Anaplasma marginale in ticks and cattle. The probe was labeled with digoxigenin 11-dUTP by polymerase chain reaction. The probe was tested on bovine blood and was found to be a sensitive and specific detection method for A. marginale in cattle. The DNA probe was then adapted for in situ hybridization (ISH) of A. marginale in Dermacentor andersoni and D. variabilis ticks infected either as nymphs or adults. One-half of each tick was studied with ISH while the other half was examined with light and electron microscopy. In male ticks infected as adults, tick gut cells first became infected with A. marginale while ticks fed on an infected calf, and they remained infected as they transmission fed on a second, susceptible calf. At the onset of transmission feeding, salivary glands became infected with A. marginale. During transmission feeding infection was also observed in interstitial, reproductive, skeletal muscle, fat body and Malpighian tubule tissue, resulting in a generalized A. marginale infection. When adult ticks that acquired infection as nymphs were examined with ISH and microscopy, gut tissues of both D. andersoni and D. variabilis became infected with A. marginale. However, salivary gland infection was seen only in D. variabilis, even though both species of ticks transmitted A. marginale to susceptible calves. A. marginale was not seen with ISH or microscopy in hemocytes collected from both species of ticks and, thus, hemocytes do not appear to play a role in the development of A. marginale in ticks.

Anaplasma↗
PubMed1998

Alignment and category learning.

Recent research shows that similarity comparisons involve an alignment process in which features are placed into correspondence. In 6 studies, the authors showed that alignment is involved in category learning as well. Within a category, aligned matches (feature matches occurring on the same dimension) facilitate learning more than nonaligned matches do (matches on different dimensions), although nonaligned matches still facilitate learning relative to nonmatches. Analogously, feature matches that cross category boundaries hurt learning more if they occur on the same versus a different dimension, and cross-category feature matches on different dimensions hurt learning relative to nonmatching features. Representational assumptions of category learning models must be modified to account for the differences between aligned and nonaligned feature matches.

Humans↗
PubMed1998

Genetic and immunologic analyses of PlpE, a lipoprotein important in complement-mediated killing of Pasteurella haemolytica serotype 1.

Pasteurella haemolytica serotype 1 is the bacterium most commonly associated with bovine shipping fever. The presence of antibodies against P. haemolytica outer membrane proteins (OMPs) correlates statistically with resistance to experimental P. haemolytica challenge in cattle. Until now, specific P. haemolytica OMPs which elicit antibodies that function in host defense mechanisms have not been identified. In this study, we have cloned and sequenced the gene encoding one such protein, PlpE. Analysis of the deduced amino acid sequence revealed that PlpE is a lipoprotein and that it is similar to an Actinobacillus pleuropneumoniae lipoprotein, OmlA. Affinity-purified, anti-PlpE antibodies recognize a protein in all serotypes of P. haemolytica except serotype 11. We found that intact P. haemolytica and recombinant E. coli expressing PlpE are capable of absorbing anti-PlpE antibodies from bovine immune serum, indicating that PlpE is surface exposed in P. haemolytica and assumes a similar surface-exposed conformation in E. coli. In complement-mediated killing assays, we observed a significant reduction in killing of P. haemolytica when bovine immune serum that was depleted of anti-PlpE antibodies was used as the source of antibody. Our data suggest that PlpE is surface exposed and immunogenic in cattle and that antibodies against PlpE contribute to host defense against P. haemolytica.

Amino Acid Sequence↗
PubMed1998

Characterization of a Pasteurella haemolytica A1 mutant deficient in production of three membrane lipoproteins.

OBJECTIVE: To determine whether a Pasteurella haemolytica A1 mutant that is unable to produce membrane lipoproteins has reduced susceptibility to complement-mediated killing, and to characterize the mutant strain. SAMPLE POPULATION: 12 sera from cattle resistant to P haemolytica challenge exposure after vaccination with P haemolytica or its antigens, or after natural exposure. PROCEDURES: Complement-mediated killing assays were performed, using wild-type and mutant strains and, as antibody source, various immune sera from cattle that were resistant to P haemolytica challenge exposure. Antibody response to whole-cell antigens produced by mutant and wild-type strains, production of outer membrane proteins and iron-regulated outer membrane proteins by the 2 strains, and growth of the 2 strains in various media were analyzed. RESULTS: Compared with wild-type P haemolytica, the lipoprotein mutant strain had increased susceptibility to bovine complement-mediated killing. Aside from the lipoproteins that are not produced by the mutant, immunoblot analysis did not reveal differences between immunoreactive antigens that are produced by the 2 strains. Some iron-regulated, outer membrane proteins, which usually are only produced by P haemolytica under iron-deficient conditions, were produced constitutively by the mutant. The mutant grew to a lower final cell density and at a lower rate under conditions likely to reflect those encountered in vivo. CONCLUSIONS: Lack of 3 membrane lipoproteins resulted in enhanced susceptibility to bovine complement-mediated killing. Site-specific mutagenesis of genes encoding P haemolytica membrane lipoproteins alters production of iron-regulated outer membrane proteins by P haemolytica. Growth characteristics of the mutant suggested that it may have reduced capacity for survival in vivo.

Animals↗
PubMed1997

Characterization of a new isolate of Ehrlichia platys (Order Rickettsiales) using electron microscopy and polymerase chain reaction.

A mixed-breed pup approximately 3 months old obtained in north central Oklahoma by the Laboratory Animal Resources Unit of Oklahoma State University presented with platelet inclusions. The dog developed severe thrombocytopenia (< 10,000 microliters-1) following the appearance of inclusions. Blood films were monitored daily and when about 75% of platelets had inclusions, samples were collected in EDTA and processed for electron microscopic (EM) studies and polymerase chain reaction (PCR). EM studies on glutaraldehyde-fixed buffy coat revealed rickettsia-like inclusions in numerous platelets. Serologic examination, using Ehrlichia platys antigen, showed high titre suggestive of E. platys infection. PCR primers derived from a highly variable region of the 16S rRNA gene sequence of E. platys were used to specifically amplify that region of the parasite's DNA. Sequencing of the PCR product obtained by general Ehrlichia primers showed one nucleotide difference from the published sequence for E. platys which suggests possible strain variation of this intracellular parasite. Our results indicate that PCR may be a useful tool in the diagnosis of E. platys infection and that, like other Ehrlichia spp., E. platys isolates may vary.

Animals↗
PubMed1997

Outer membrane proteins of bovine Pasteurella multocida serogroup A isolates.

The outer membrane proteins (OMPs) of P. multocida serotypes A3 (7 isolates), A4 (2 isolates), A3,4 and A2 (one isolate each) obtained from pneumonic cattle (10 isolates) and from one pig isolate were investigated to identify potential immunogens. SDS-PAGE of P. multocida OM isolated by SDG centrifugation of spheroplasts revealed eight major OMPs. Outer membranes isolated by sarcosyl extraction or SDG had similar protein composition on Coomassie blue-stained SDS-PA gel and on immunoblots. Two major OMPs (M(r)s of 35 and 46 kDa at 100 degrees C) demonstrated heat modifiability with apparent M(r)s of 30 and 34 kDa at 37 degrees C, respectively. The N-terminal aa sequences of these heat modifiable proteins revealed homology with E. coli OmpA and Hib P1 proteins, respectively. Protease treatment of whole cells followed by western immunoblots using bovine convalescent sera identified several immunogenic, surface-exposed and conserved OMPs among the eleven P. multocida isolates examined. The whole organism SDS-PAGE profiles of the eleven P. multocida isolates differed such that six patterns were seen. These patterns could potentially be used as a typing system for P. multocida bovine isolates based on the molecular weights of whole cell proteins. The above observations have potentially important implications relative to the immunity to infection.

Amino Acid Sequence↗
PubMed1997

The effects of prior processing episodes on basic-level superiority.

Four experiments were conducted to investigate the effects of prior processing episodes on people's preference for categorizing objects at the basic level (e.g. dog) relative to their preference for categorizing at the superordinate (e.g. animal) and the subordinate (e.g. Dalmation) levels. The prior processing episode in Experiment 1 was designed to induce subjects to activate representations at the superordinate level, and those in the remaining experiments were designed to induce subjects to differentiate objects at the subordinate level. After the prior processing episodes, subjects performed either a free naming or a picture categorization task that required them to decide whether an illustrated object belonged to a specified category. Results showed that prior processing episodes modestly reduced the superiority of basic level to superordinate level and subordinate level in categorization but not in free naming. The results suggest that the basic-level advantage is subject to the effects of context, but the effects are not as strong as the context effects on other aspects of categorization behaviour (e.g. rating typicality of a category member). Hence, the preference for the basic level is a somewhat more stable, invariant aspect of conceptual representation. Possible determinations of this stability are discussed.

Cognition↗
PubMed1997

Purification and partial characterization of the OmpA family of proteins of Pasteurella haemolytica.

This study was conducted to partially characterize and identify the purity of two major outer membrane proteins (OMPs) (with molecular weights of 32,000 and 35,000 [32K and 35K, respectively]) of Pasteurella haemolytica. The 35K and 32K major OMPs, designated Pasteurella outer membrane proteins A and B (PomA and PomB, respectively), were extracted from P. haemolytica by solubilization in N-octyl polyoxyl ethylene. The P. haemolytica strain used was a mutant serotype A1 from which the genes expressing the 30-kDa lipoproteins had been deleted. PomA and PomB were separated and partially purified by anion-exchange chromatography. PomA but not PomB was heat modifiable. The N-terminal amino acid sequences of the two proteins were determined and compared with reported sequences of other known proteins. PomA had significant N-terminal sequence homology with the OmpA protein of Escherichia coli and related proteins from other gram-negative bacteria. Moreover, polyclonal antiserum raised against the E. coli OmpA protein reacted with this protein. PomA was surface exposed, was conserved among P. haemolytica biotype A serotypes, and had porin activity in planar bilayers. No homology between the N-terminal amino acid sequence of PomB and those of other known bacterial proteins was found. Cattle vaccinated with live P. haemolytica developed a significant increase in serum antibodies to partially purified PomA, as shown by enzyme-linked immunosorbent assays, and to purified PomA and PomB, as detected on Western blots and by densitometry.

Amino Acid Sequence↗
PubMed1997

Use of a nonradioactive DNA probe for detection of Anaplasma marginale infection in field cattle: comparison with complement fixation serology and microscopic examination.

A sensitive Anaplasma marginale-specific 409-base pair DNA probe was developed in a previous study for detection of A. marginale infection in experimentally infected cattle with a test that employed slot-blot and in situ hybridization. To test the suitability of the probe to detect A. marginale in the blood of naturally infected carrier cattle, slot-blot hybridization was used to determine the infection rate of A. marginale in cattle from 3 geographic areas in Oklahoma. For comparison, blood samples from the same cattle were also examined by light microscopy and were tested by the complement fixation test. For the DNA hybridization assay, the probe was labeled with digoxigenin 11-dUTP by polymerase chain reaction (PCR). DNA was extracted from blood using the QIAamp blood kit and then applied to a nylon membrane and hybridized with the probe. The study herds consisted of 31 beef cows in Harper County, OK, and 42 and 70 dairy cows from Payne and Pittsburg counties, OK, respectively. In the 3 herds, 80.6%, 92.8%, and 57.1% of the cows were positive for A. marginale as assessed with the DNA hybridization assay. In contrast, only 25.8% and 2.86% were complement fixation positive in 2 herds, and no complement fixation positives were found in 1 herd. Uncountable parasitemia that was too low to accurately determine (< 0.01%) from 29.0%, 4.8%, and 11.4% of the samples, respectively, was demonstrated by microscopic examination. All samples positive by complement fixation and microscopic examination had positive probe reactions in the DNA hybridization assay. Therefore, the PCR-mediated nonradioactive DNA probe described here may be useful in epidemiologic investigations and in identification of carrier cattle. This assay could be adapted for use in diagnostic laboratories because it is sensitive, specific, nontoxic, quickly executed, and inexpensive.

Anaplasma↗