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Biomedical subjects

G L Murphy

Publications and source records attributed to G L Murphy.

At least 73 records · Page 4Linked to original sources
PubMed1990

Interpretation of verb phrase anaphora: influences of task and syntactic context.

When listeners hear a sentence like "Will Carey do it?" they must find an interpretation of the phrase "do it", which is an anaphor replacing a full verb phrase (VP). To accomplish this task, listeners may use two sources of information: finding a recent VP that is syntactically appropriate, or using pragmatics to find a recent discourse event that plausibly completes the sentence. One theory of anaphor comprehension says that listeners use both sources of information in a competition for the best antecedent. Another theory says that listeners use only one of those sources, depending on the syntactic class of anaphor. Two experiments are reported, one using a reading time technique and one a sensicality judgement task. The experiments varied the distance of the antecedent from the anaphor, the material that intervened between the antecedent and anaphor, and the syntactic class of the anaphor. In the reading task, the results followed the predictions of the two-source competition theory, as a number of effects were observed, but none of them depended on the anaphor's syntactic class. In the judgement task, however, the type of anaphor did influence judgement time. The overall results suggest that there are important differences between simple comprehension tasks and metalinguistic judgements, and that past empirical conflicts may be explicable on this basis.

Adult↗
PubMed1990

Converging operations on a basic level in event taxonomies.

Research on object concepts has identified one level of abstraction as "basic" in cognition and communication. We investigated whether concepts for routine social events have a basic level by replicating the converging operations used to investigate object concepts. In Experiment 1, subjects were presented with event names from a taxonomy and were asked to list the actions comprising the event. Many more actions were listed at the middle than at the highest taxonomic level, without a further increase at the most specific level, paralleling the pattern of superordinate-, basic-, and subordinate-level object concepts. From these action lists, brief stories were composed for each event. In Experiment 2, subjects made pairwise similarity judgments on the stories. The mean similarity of events increased with specificity, as expected. But differentiation of categories (within-category similarity compared to between-category similarity) was highest for super-ordinates, contrary to results with object categories. In Experiment 3, subjects were fastest in recognizing actions as belonging to events named at the basic level. In Experiment 4, subjects predominantly chose basic-level terms to name stories. We conclude that event taxonomies do show basic-level structure, albeit a less sharply defined and less stable structure than in object taxonomies. The benefits and hazards of extending models of object concepts to other entities, such as social events, are discussed.

Adult↗
PubMed1989

Phase variation of gonococcal protein II: regulation of gene expression by slipped-strand mispairing of a repetitive DNA sequence.

Expression of outer membrane protein II (P.II) of Neisseria gonorrhoeae is subject to reversible phase variation at a rate of 10(-3)-10(-4)/cell/generation. The signal peptide coding regions of P.II genes contain variable numbers of tandem repeats of the sequence CTCTT. Changes in the number of CTCTT units, leading to frameshifting within the gene, are responsible for changes in P.II expression. Phase variation mediated by the CTCTT repeat also occurred in E. coli, as assayed with a P.II-alkaline phosphatase (phoA) gene fusion. Phase variation in both the gonococcus and E. coli was recA-independent, occurred at similar rates, and involved insertions or deletions of one or more repeat units. The characteristics of the phase variation process were consistent with a model in which expression of P.II genes is regulated by slipped-strand mispairing of the DNA in the CTCTT repeat region.

Bacterial Outer Membrane Proteins↗
PubMed1989

Thyroid function and immune reactivity during metamorphosis in Xenopus laevis, the South African clawed toad.

High plasma titers of thyroid and adrenocorticoid hormones are present during the metamorphosis of Xenopus laevis. Here we examine the influence of thyroid hormones on several features of immune reactivity during this period, e.g., the capacity of thymus-derived immunocytes to reduce (immune suppression) or amplify (helper function) antibody production. Further, we test whether thyroid hormone is able to modulate the expression of putative interleukin 2 (IL-2) receptors on lectin-activated adult Xenopus splenocytes, an aspect of helper function. Finally, we have tested the ability of thyroid hormones to affect larval antibody-producing cells directly. Our data suggest that all three functions (suppressor, helper, and antibody producing) are independent of thyroid function during metamorphosis. However, the anatomical distribution of two features of immune suppression, as well as the numbers of lectin-activated splenocytes able to bind anti-IL-2 receptor antibody, were changed by thyroid function. In vivo thyroid blockade by thiourea prevented the transition from the premetamorphic to the adult pattern of distribution of the two suppressor functions; triiodothyronine in vitro stimulated an increase in the numbers of cells able to bind an IL-2 receptor antibody.

Adrenal Cortex Hormones↗
PubMed1989

Categorizing objects in isolation and in scenes: what a superordinate is good for.

Many studies have shown that subjects are faster at categorizing objects into "basic" concepts than into more general superordinate concepts. However, all of these studies have used a categorization task in which single, isolated objects are identified. There is good reason to believe that superordinate concepts are typically used to refer to collections of objects rather than to individual objects. For example, people more often use the term furniture to refer to a number of pieces of furniture rather than to name a single piece. This suggest that superordinate concepts include information about multiple objects and their common relations, particularly the typical scenes in which such objects appear. Four experiments examined this possibility by investigating whether the basic concept advantage will decrease or reverse itself when subjects are asked to categorize an object as part of a scene. The results showed that the basic-superordinate difference did decrease when subjects categorized objects in scenes. Furthermore, when an object was placed in an inappropriate scene, there was more interference for superordinate identifications. The results suggest qualitative differences in the representations of superordinate and basic concepts.

Adult↗
PubMed1988

Recombination among protein II genes of Neisseria gonorrhoeae generates new coding sequences and increases structural variability in the protein II family.

Expression of Neisseria gonorrhoeae Protein II (P.II) is subject to phase variation and antigenic variation. The P.II proteins made by one strain possess both unique and conserved antigenic determinants. To study the mechanism of antigenic variation, we cloned several P.II genes, using as probes a panel of monoclonal antibodies (MAbs) specific for unique determinants. The DNA sequences of three P.II genes showed that they shared a conserved framework, with two short hypervariable (HV) regions being responsible for most of the differences among them. We demonstrated that unique epitopes recognized by the MAbs were at least partially encoded by one of the HV regions. Moreover, we found that reassortment of the two HV regions among P.II genes occurs, generating increased structural and antigenic variability in the P.II protein family.

Antigens, Bacterial↗
PubMed1987

Chlorinated fatty acid distribution in Mycobacterium convolutum phospholipids after growth on 1-chlorohexadecane.

The composition of phospholipids from Mycobacterium convolutum R22 was determined after growth at two temperatures (20 and 30 degrees C) with 1-chlorohexadecane as the substrate. Comparisons were made with the phospholipids of cells grown on n-hexadecane. Phosphatidylinositolmannosides and phosphatidylethanolamine (PE) were the major phospholipids in n-hexadecane-grown cells. In 1-chlorohexadecane-grown cells, phosphatidylinositolmannosides were approximately half of the total phospholipids, with lesser amounts of PE and cardiolipin (CL). The relative level of PE was greater at 20 degrees C (versus that at 30 degrees C) after growth on either substrate. A determination was made of structure and positional distribution of constituent fatty acid in both CL and PE. The relative amount of unsaturated fatty acid was higher at 20 degrees C. There were two C16:1 fatty acids (C16:1 delta 9 and C16:1 delta 11), and these had positional preferences in both CL and PE. The positional sites of chlorinated fatty acids differed in both CL and PE at the two temperatures. The results confirm that microorganisms can specifically distribute chlorinated fatty acids into cellular phospholipids.

Alkanes↗
PubMed1987

Distribution of specific DNA sequences among pathogenic and commensal Neisseria species.

Several traits, including pili and the outer membrane proteins P.II and H.8, have been associated with pathogenic Neisseria species. We examined several Neisseria species for DNA sequence homology to cloned pilin, P.II, and H.8 genes. Strains of Neisseria gonorrhoeae and N. meningitidis showed hybridization to all of these genes. Commensal strains showed little hybridization to any of these genes. Strains of N. lactamica and N. cinerea showed intermediate patterns of hybridization. Generally, organisms that expressed a given trait showed DNA homology to the corresponding cloned gene. However, we observed pili on some commensal strains that did not show hybridization to the cloned gonococcal pilin gene.

Bacterial Outer Membrane Proteins↗
PubMed1985

Category differentiation in object recognition: typicality constraints on the basic category advantage.

When people are asked to decide whether an object is in a given category, they generally respond faster when the category is at the basic level (e.g., car) than when it is at the superordinate level (e.g., vehicle) or the subordinate level (e.g., sedan). Basic categories have shorter and more frequent names, are learned earlier, and are usually more highly differentiated than other categories (they are both specific and distinctive), but it is not clear which of these factors is responsible for the faster response to basic categories. In three experiments with natural language categories, we found evidence that objects can be identified fastest as members of differentiated categories, even when such categories have longer names and are learned later than less differentiated categories. Specifically, we argued that atypical subordinate categories (e.g., racing car) are highly differentiated and should therefore be responded to as fast as basic categories in object recognition. The results supported this view and also ruled out the hypothesis that objects are necessarily identified as members of basic categories before further identification. We discuss the implications of these findings for the use of category names as definite descriptions in discourse.

Discrimination Learning↗
PubMed1985

Comparison of environmental radiation dosimetry and gamma-ray spectroscopy.

During the period 1975-1980, direct radiation dose rates were measured at 16 fixed locations in the vicinity of the Joseph M. Farley Nuclear Plant, Houston County, AL, by exposure of TLDs which were read quarterly. The average quarterly dose rates using LiF chips varied widely over the 6-yr period and were divided into 2 distinct population groups of 4 and 2 yr each, corresponding to the vendor labs supplying and reading the TLDs. The simultaneous exposure of CaSO4:Dy TLDs for 2 yr gave a third set of values which fell between the 2 LiF groups. During the period December 1976-November 1980, simultaneous pressurized ion chamber (PIC) and in situ Ge(Li) gamma-ray spectroscopy measurements were made at the same locations at approx. 6-month intervals. The PIC exposure rate values were relatively constant for each location except for 1 measurement at the end of a long dry period broken by showers of rain. The average PIC dose rate values were in good agreement with the average 2-yr LiF TLD values. Also, good agreement resulted from converting the in situ radioactivity values to dose rates using conversion values previously published. Using the in situ Ge(Li) gross gamma count rates, and a new equation developed by the authors for calculating exposure rate, resulted in excellent agreement with both individual and average PIC values. The natural radioactivity and fallout 137Cs in the soil showed little variation for a specific site, but varied widely between some sites. With the event of rain at the end of a long dry period, there was a large increase in 214Bi and 214Pb activity detected. Short half-life manmade radionuclides were seen for a few months following several atmospheric nuclear tests by the People's Republic of China.

Alabama↗
PubMed1984

Assimilation of chlorinated alkanes by hydrocarbon-utilizing fungi.

The fatty acid compositions of two filamentous fungi (Cunninghamella elegans and Penicillium zonatum) and a yeast (Candida lipolytica) were determined after the organisms were grown on 1-chlorohexadecane or 1-chlorooctadecane. These organisms utilized the chlorinated alkanes as sole sources of carbon and energy. Analyses of the fatty acids present after growth on the chlorinated alkanes indicated that 60 to 70% of the total fatty acids in C. elegans were chlorinated. Approximately 50% of the fatty acids in C. lipolytica were also chlorinated. P. zonatum contained 20% 1-chlorohexadecanoic acid after growth on either substrate but did not incorporate C18 chlorinated fatty acids.

Alkanes↗
PubMed1983

Incorporation of chlorinated alkanes into fatty acids of hydrocarbon-utilizing mycobacteria.

The cellular fatty acid composition of Mycobacterium vaccae JOB5 and Mycobacterium convolutum R22 was examined after growth on n-alkanes and compared with the fatty acids of the organisms after growth on 1-chlorohexadecane and 1-chlorooctadecane. Growth on n-alkanes resulted in normal fatty acid profiles. Mass spectral analyses indicated that, after growth on the terminally chlorinated n-alkanes, 75 to 86% of the fatty acids in M. convolutum and ca. 55% of the fatty acids in M. vaccae contained chlorine. Neither organism could utilize chloroacetate or 3-chloropropionate as sole source of carbon and energy. When these compounds were added to a growth medium with n-hexadecane as substrate, there was no evidence that chlorinated fatty acids were produced. Terminally chlorinated n-alkanes can be added to the list of n-alkanes, alkenes, and cyclohexylalkane derivatives that can be directly incorporated into cellular fatty acids of hydrocarbon-utilizing organisms.

Acetates↗
PubMedDate not supplied

Naturally occurring Ehrlichia chaffeensis infection in coyotes from Oklahoma.

A nested polymerase chain reaction assay was used to determine the presence of Ehrlichia chaffeensis, E. canis, and E. ewingii DNA in blood samples of free-ranging coyotes from central and northcentral Oklahoma. Of the 21 coyotes examined, 15 (71%) were positive for E. chaffeensis DNA; none was positive for E. canis or E. ewingii. Results suggest that E. chaffeensis infections are common in free-ranging coyotes in Oklahoma and that these wild canids could play a role in the epidemiology of human monocytotropic ehrlichiosis.

Animals↗