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Biomedical subjects

K E Johnson

Publications and source records attributed to K E Johnson.

At least 19 recordsLinked to original sources
PubMed2002

Comparison of pregnancy outcome in mares among methods used to evaluate and select spermatozoa for insemination.

An artificial insemination dose for mares consisting of 500 million progressively motile spermatozoa is considered "standard" by most clinicians. However, little information is available directly comparing pregnancy outcome among methods of evaluating and selecting spermatozoa for insemination. The objective of this study was to determine if the method of spermatozoal evaluation and selection influences fertility as measured by pregnancy outcome. Mares were inseminated with 100 or 500 million spermatozoa that were selected for progressive motility, normal morphology, hypoosmotic swelling or absolute number regardless for evaluation method or quality. Thirty-two breeding cycles were tested for each treatment group and at each spermatozoal dose. Pregnancy outcomes were 44 and 41%, 55 and 41%, 39 and 31%, and 45 and 41%, for the 100 and 500 million progressively motile, morphologically normal, hypoosmotic swelling positive and absolute number treatment groups, respectively. Pregnancy outcome did not differ among methods of spermatozoal evaluation and selection for artificial insemination in the 100 (P=0.52) or 500 (P=0.78) million spermatozoa groups. Also the total number of spermatozoa and the absolute number of progressively motile, morphologically normal or hypoosmotic swelling positive spermatozoa inseminated, were not closely associated with pregnancy outcome in the 100 (P=0.24, 0.29, 0.33 and 0.38, respectively) or 500 (P=0.20, 0.84, 0.50 and 0.74, respectively) million spermatozoa groups. In this study, we found that the method of spermatozoal evaluation did not offer an advantage for pregnancy when used to select spermatozoa for insemination at the doses tested. These results were surprising, as we expected there would be differences among the evaluation methods. Instead, we found that evaluating spermatozoa offered no advantage for pregnancy over simply inseminating with a specified number of spermatozoa not selected for any particular characteristic under the conditions of our experiment.

Animals↗
PubMed2002

The North-West Diabetes Foot Care Study: incidence of, and risk factors for, new diabetic foot ulceration in a community-based patient cohort.

AIMS: To determine the incidence of, and clinically relevant risk factors for, new foot ulceration in a large cohort of diabetic patients in the community healthcare setting. METHODS: Diabetic patients (n = 9710) underwent foot screening in six districts of North-west England in various healthcare settings. All were assessed at baseline for demographic information, medical and social history, neuropathy symptom score, neuropathy disability score, cutaneous pressure perception (insensitivity to the 10 g monofilament), foot deformities, and peripheral pulses. Two years later, patients were followed up via postal questionnaire to determine the incidence of new foot ulcers. Cox's proportional hazards regression analysis was used to determine the independent, relative risk of baseline variables for new foot ulceration. RESULTS: New foot ulcers occurred in 291/6613 patients who completed and returned their 2-year follow-up questionnaire (2.2% average annual incidence). The following factors were independently related to new foot ulcer risk: ulcer present at baseline (relative risk (95% confidence interval)) 5.32 (3.71-7.64), past history of ulcer 3.05 (2.16-4.31), abnormal neuropathy disability score (> or = 6/10) 2.32 (1.61-3.35), any previous podiatry attendance 2.19 (1.50-3.20), insensitivity to the 10 g monofilament 1.80 (1.36-2.39), reduced pulses 1.80 (1.40-2.32), foot deformities 1.57 (1.22-2.02), abnormal ankle reflexes 1.55 (1.01-2.36) and age 0.99 (0.98-1.00). CONCLUSIONS: More than 2% of community-based diabetic patients develop new foot ulcers each year. The neuropathy disability score, 10 g monofilament and palpation of foot pulses are recommended as screening tools in general practice.

Adolescent↗
PubMed2001

An active site tyrosine influences the ability of the dimethyl sulfoxide reductase family of molybdopterin enzymes to reduce S-oxides.

Dimethyl sulfoxide reductase (DMSOR), trimethylamine-N-oxide reductase (TMAOR), and biotin sulfoxide reductase (BSOR) are members of a class of bacterial oxotransferases that contain the bis(molybdopterin guanine dinucleotide)molybdenum cofactor. The presence of a Tyr residue in the active site of DMSOR and BSOR that is missing in TMAOR has been implicated in the inability of TMAOR, unlike DMSOR and BSOR, to utilize S-oxides. To test this hypothesis, Escherichia coli TMAOR was cloned and expressed at high levels, and site-directed mutagenesis was utilized to generate the Tyr-114 --> Ala and Phe variants of Rhodobacter sphaeroides DMSOR and insert a Tyr residue into the equivalent position in TMAOR. Although all of the mutants turn over in a manner similar to their respective wild-type enzymes, mutation of Tyr-114 in DMSOR results in a decreased specificity for S-oxides and an increased specificity for trimethylamine-N-oxide (Me(3)NO), with a greater change observed for DMSOR-Y114A. Insertion of a Tyr into TMAOR results in a decreased preference for Me(3)NO relative to dimethyl sulfoxide. Kinetic analysis and UV-visible absorption spectra indicate that the ability of DMSOR to be reduced by dimethyl sulfide is lost upon mutation of Tyr-114 and that TMAOR does not exhibit this activity even in the Tyr insertion mutant.

Amino Acid Sequence↗
PubMed2001

Impact of varying levels of expertise on decisions of category typicality.

Experts on domains of basic level object categories possess extensive knowledge of features used to both individuate and categorize groups of similar members. Two studies were conducted to determine the impact of high knowledge on intermediate and advanced experts' typicality decisions for basic and subordinate level category exemplars, and to investigate whether the pattern of influence of factors (in particular, central tendency and subjective familiarity) remained fixed throughout the continuum of expertise. Example goodness increased as a function of the level of specificity of the category for which typicality was rated. Subjective familiarity was the principal determinant of typicality for individuals with high knowledge, whereas central tendency was related to typicality when knowledge was not particularly high. Advanced and intermediate experts produced similar ratings of typicality, indicating that individuals' decisions of typicality do not change markedly once intermediate levels of competency have been attained. The incorporation of knowledge effects into models of semantic memory, as well as interactions among knowledge, psychological factors, and environmental factors in determining typicality, are discussed.

Adult↗
PubMed2001

Using immunohistochemistry to study plant metabolism: the examples of its use in the localization of amino acids in plant tissues, and of phosphoenolpyruvate carboxykinase and its possible role in pH regulation.

To understand many aspects of the metabolism of complex plant structures such as leaves, fruit and roots it is important to understand how metabolic processes are compartmentalized between tissues. The aim of this article is to show how immunohistochemistry, in conjunction with biochemical and physiological studies, is useful in understanding both the function of an enzyme in a tissue and metabolic processes occurring in plant tissues. This is illustrated by two examples. Firstly, the use of immunohistochemisty in the localization of amino acids in plant tissues is described. Secondly, the use of immunohistochemistry in understanding the function of an enzyme in a tissue and the metabolic processes occurring within the tissue is described. To illustrate this the example of phosophoenolpyruvate carboxykinase (PEPCK), an enzyme which is present in many plant tissues in which its function is unknown, is used. Evidence is provided that PEPCK may play a role in pH regulation in tissues active in the metabolism of nitrogen.

Amino Acids↗
PubMed2000

The CXCR4 agonist ligand stromal derived factor-1 maintains high affinity for receptors in both Galpha(i)-coupled and uncoupled states.

The alpha chemokine receptor CXCR4 and its only characterized chemokine ligand, stromal cell-derived factor-1 (SDF-1), are postulated to be important in the development of the B-cell arm of the immune system. In addition, CXCR4 is a critical coreceptor in support of viral entry by T-cell line tropic strains (X4) of the Human Immunodeficiency Virus Type 1 (HIV-1), viral variants which predominate in some infected individuals in end stage disease. SDF-1 can block X4-tropic HIV-1 infection of CD4+ target cells in vitro, and allelic variants of the human gene encoding SDF-1 in vivo correlate with delayed disease progression. Therefore, CXCR4 may be an appropriate target for therapeutic intervention in acquired immunodeficiency syndrome (AIDS), and knowledge of the pharmacology of SDF-1 binding to its cognate receptor will be important in the interpretation of these experiments. We report here a Kd derived using a competition binding assay of 4.5 nM for CXCR4 endogenously expressed on peripheral blood monocytes and T-cells. This affinity is similar to that which SDF-1 exhibits when binding to endogenous CXCR4 on an established immortal Jurkat T-cell line as well as recombinant CXCR4 transfected into Chinese Hamster Ovary (CHO) cells. We also demonstrate that the determined affinity of SDF-1 for CXCR4 is reflective of its ability to induce a CXCR4-mediated signal transduction in these different cell types. Furthermore, using Bordetella pertussis toxin, we observe that high affinity binding of SDF-1 to CXCR4 is independent of the G-protein coupled state of the receptor, as uncoupling of G-protein did not lead to the appearance of measurable low affinity SDF-1 binding sites. Moreover, binding affinity and receptor number were unaffected by uncoupling for both recombinant and endogenously expressed CXCR4. Thus, SDF-1 is novel among agonist ligands of G protein-coupled receptors in that it appears to have equal affinity for both the G protein-coupled and uncoupled states of CXCR4.

Animals↗
PubMed2000

Quantitative determination of a chemically modified hammerhead ribozyme in blood plasma using 96-well solid-phase extraction coupled with high-performance liquid chromatography or capillary gel electrophoresis.

Versatile bioanalytical assays to detect chemically stabilized hammerhead ribozyme and putative ribozyme metabolites from plasma are described. The extraction protocols presented are based on serial solid-phase extractions performed on a 96-well plate format and are compatible with either IEX-HPLC or CGE back-end analysis. A validation of both assays confirmed that both the HPLC and the CGE methods possess the required linearity, accuracy, and precision to accurately measure concentrations of hammerhead ribozyme extracted from plasma. These methods should be of general use to detect and quantitate ribozymes from other biological fluids such as serum and urine.

Animals↗
PubMed2000

The effect of an interactive experience on music majors' perceptions of music for deaf students.

The purpose of this study was to examine the effect of an interactive experience on music majors' perceptions of music experiences for deaf students. Twenty-three members of a pre-existing college brass ensemble served as subjects, and a 1-hour interactive concert/presentation for 10 deaf elementary children served as the independent variable. The interactive experience was designed to provide social, musical, and educational interactions between the college musicians and the deaf children. A pretest-posttest design was utilized, and the dependent variable was a questionnaire designed to examine the subjects' perceptions regarding music for deaf students, including how prepared, comfortable, and willing they felt to provide music experiences for deaf students. Results reveal that this single interactive experience had a significant effect on the subjects' perceptions of the value of music in the education of deaf children (p <.05). Although the pretest and posttest scores indicate that the subjects felt apprehensive about their preparedness to work with deaf students, the subjects felt significantly more positive about their preparedness following the interaction (p <.001). An analysis of open comments indicates that the subjects perceived the experience as (a) very positive, (b) increasing their knowledge and perception of music for deaf students, (c) helping them better relate to the deaf population, (d) promoting interest in similar experiences and in gaining more information, and (e) eliciting a feeling that future teachers should have similar experiences. Quotes from the subjects are given, and implications for teacher training/music therapy programs are discussed.

Adult↗
PubMed2000

An analysis of trends, perceptions, and use patterns of electronic medical records among US family practice residency programs.

BACKGROUND AND OBJECTIVES: This study intended to quantify electronic medical record (EMR) use in family practice residencies, associate program characteristics with EMR use, and identify perceptions and issues about the use of EMRs. METHODS: A survey was mailed to all 454 US family practice residency programs, with a 72% response rate. The survey, which was pretested and revised, was designed to identify benefits, problems, perceptions, and trends regarding the use of EMRs. RESULTS: Fifty-five of 329 programs (17%) were using an EMR, while 10 (3%) had used an EMR but discontinued. Programs in the South reported the highest EMR use (21%, 21/99), and those in the North Central region reported the lowest use (11%, 11/102). EMR use was highest in university settings (19%, 15/81), programs offering fellowships (26%, 24/92), new programs (36%, 18/48), and programs that require research (22%, 20/91). Of the 329 programs that responded, 43% (143 programs) reported having information systems (IS) committees. Of the 55 programs currently using EMRs, 78% had at least one full-time equivalent IS technician. Of programs that discontinued use, software inadequacy was the most frequently cited reason (40%, 4/10). Programs that had never used EMR systems (n = 264) were more likely than those that had used EMRs (n = 65) to favorably perceive EMRs with respect to 1) meeting program requirements (44% versus 34%), 2) documenting improved patient care (65% versus 43%), 3) providing a reliable research database (94% versus 55%), and 4) documenting resident experience (92% versus 53%). Of the 264 (80%) programs that had never used an EMR, 172 (65%) plan to implement one. CONCLUSIONS: EMR use is low among US family practice residency programs, but some success in implementation of EMRs has been achieved. Based on the responses to this survey, use will likely increase from 55 of 329 programs (17%) to 153 of 329 (47%) by 2000.

Family Practice↗
PubMed1998

Blastomeres show differential fate changes in 8-cell Xenopus laevis embryos that are rotated 90 degrees before first cleavage.

To study the mechanisms of dorsal axis specification, the alteration in dorsal cell fate of cleavage stage blastomeres in axis-respecified Xenopus laevis embryos was investigated. Fertilized eggs were rotated 90 degrees with the sperm entry point up or down with respect to the gravitational field. At the 8-cell stage, blastomeres were injected with the lineage tracers, Texas Red- or FITC-Dextran Amines. The distribution of the labeled progeny was mapped at the tail-bud stages (stages 35-38) and compared with the fate map of an 8-cell embryo raised in a normal orientation. As in the normal embryos, each blastomere in the rotated embryos has a characteristic and predictable cell fate. After 90 degrees rotation the blastomeres in the 8-cell stage embryo roughly switched their position by 90 degrees, but the fate of the blastomeres did not simply show a 90 degrees switch appropriate for their new location. Four types of fate change were observed: (i) the normal fate of the blastomere is conserved with little change; (ii) the normal fate is completely changed and a new fate is adopted according to the blastomere's new position: (iii) the normal fate is completely changed, but the new fate is not appropriate for its new position; and (4) the blastomere partially changed its fate and the new fate is a combination of its original fate and a fate appropriate to its new location. According to the changed fates, the blastomeres that adopt dorsal fates were identified in rotated embryos. This identification of dorsal blastomeres provides basic important information for further study of dorsal signaling in Xenopus embryos.

Animals↗
PubMed1998

The effectiveness of a magnetized water oral irrigator (Hydro Floss) on plaque, calculus and gingival health.

The purpose of this study was to evaluate the effects of a magnetized water oral irrigator on plaque, calculus and gingival health. 29 patients completed this double-blind crossover study. Each patient was brought to baseline via an oral prophylaxis with a plaque index < or = 1 and a gingival index < or = 1. Subjects used the irrigator for a period of 3 months with the magnet and 3 months without the magnet. After each 3 month interval, data were collected using the plaque index, gingival index, and accretions index. The repeated measures analysis on plaque, gingival and calculus indices yielded a statistically-significant period effect for PlI (p=0.0343), GI (p=0.0091), and approached significance for calculus (p=0.0593). This meant that the effect of irrigation resulted in a decrease of all indices over time. Therefore, the treatment effect on each index was evaluated using only the measurements obtained at the end of the first period (i.e., assuming a parallel design). Irrigation with magnetized water resulted in 64% less calculus compared to the control group. The reduction was statistically significant (p< or =0.02). The reduction by 27% in gingival index was not statistically significant. The reduction in plaque was minimal (2.2%). A strong positive correlation between the plaque index and the Watt accretion index was observed. The magnetized water oral irrigator could be a useful adjunct in the prevention of calculus accumulation in periodontal patients, but appears to have minimal effect on plaque reduction. The results indicated a clinical improvement in the gingival index, but this was not a statistically significant finding.

Analysis of Variance↗
PubMed1998

Impact of intuitive theories on feature recruitment throughout the continuum of expertise.

Expertise in object domains involves both the perceptual learning of the differentiating and higher order features that are indicative of concepts and the elaboration of intuitive theories. Triad-similarity judgments, feature-salience ratings, and verbal protocols were used to investigate the effects of theories on the recruitment of features across different categorization contexts, as well as the degree to which expert categorization skills transferred to less familiar domains. Whereas novices considered features that indicated overall similarity to be more perceptually salient than were modified parts that indicated taxonomic relations, experts found them equally salient. Experts' theories were instrumental in directing feature recruitment in contexts involving identification, image generation, and similarity decisions. Experts' theories also supported the transfer of categorization skills to related, less familiar domains. The relation of mutual dependence between perceptual learning and theory development throughout the continuum of expertise is considered.

Adult↗
PubMed1998

The cost of inpatient endometriosis treatment: an analysis based on the Healthcare Cost and Utilization Project Nationwide Inpatient Sample.

OBJECTIVE: To determine the prevalence and cost of endometriosis-related hospitalizations based on the Nationwide Inpatient Sample (NIS) from the Healthcare Cost and Utilization Project (HCUP-3). STUDY DESIGN: Retrospective analysis based on nationwide clinical practice data. PATIENTS AND METHODS: Data were obtained for 1991 and 1992 from the HCUP-NIS database, which was a 20% sample of all US hospital discharges. ICD-9 codes (236.0, 617.0 to 617.9) were used to identify females, aged 15 to 54, with endometriosis as a diagnosis. The distribution of endometriosis admissions by admission type, length of stay (LOS), mean total charge, specific types of endometriosis, principal procedures, and other diagnosed diseases was described. RESULTS: In 1991 and 1992, 37,273 (22.6/1000) and 38,834 (23.7/1000) hospital admissions, respectively, were for endometriosis (as any diagnosis). The average LOS and total hospital charges for endometriosis as the primary diagnosis were 3.8 days and $6,597 for 1991, and 3.5 days and $7,450 for 1992. Most endometriosis admissions occurred in females aged 35 to 49. About 87% of the endometriosis hospitalizations were routine admissions. The most common diagnosis was endometriosis of the uterus (51%); the most common procedure was a total abdominal hysterectomy (55%-60%). Older and African-American patients had the longest LOS and the highest total charges. The estimated total hospitalization costs, as represented by hospital charges, for women with endometriosis as the primary diagnosis in the United States were $504 million for 1991 and $579 million for 1992. CONCLUSION: Endometriosis-related hospitalization is a major burden on healthcare systems.

Adolescent↗
PubMed1997

Fates of the blastomeres of the 32-cell stage Pleurodeles waltl embryo.

Cell fate of the blastomeres at the 32-cell stage in the Pleurodeles waltl embryo was analyzed by injection of rhodamine or fluorescein lysinated-dextran (RLDx or FLDx). At the tailbud stage, the progeny of each blastomere contributed to more than one germ layer with unequal distribution along the anteroposterior and dorsoventral axis. Such a regionalized positioning of the descendants of the 32-cell blastomeres was found in the neuroectoderm, the epidermis, the notochord, the somites, the lateral plate, and the endoderm, but not in the head mesenchyme, the pronephros, or the blood islands. Results of double labeling of juxtaposed blastomeres showed that cell mixing and rearrangement take place during organ formation. Results are compared with those of the 32-cell stage fate map in Xenopus and Rana and reveal the more restricted fate of 32-cell stage blastomeres in Pleurodeles germ layers.

Animals↗
PubMed1997

Development of children's understanding of basic-subordinate inclusion relations.

Four studies focused on developmental differences in the representation of basic-subordinate inclusion relations. Tests of comprehension and production of category names, induction, and responses to direct questions pertaining to inclusion revealed a marked developmental gap between the production of subordinate category names and complete understanding of basic-subordinate inclusion relations. However, even 3-year-olds showed rudimentary knowledge of the asymmetry of inclusion. Discrepancies between children's performance on categorization tasks involving familiar and unfamiliar subordinate categories suggest that understanding of the logical nature of inclusion relations is constructed through the integration of categorical knowledge from familiar domains. Interactions among the knowledge base, pragmatic sensitivity, and information processing efficiency in the development of inclusion are discussed.

Age Factors↗
PubMed1997

Effects of varying levels of expertise on the basic level of categorization.

Six experiments were conducted on the effects of expertise on basic-level categorization. Individuals with varying levels of knowledge about songbirds generated lists of attributes, named objects, identified and discriminated among object silhouettes, verified category membership at 4 hierarchical levels, and visually identified songbirds primed either by species-specific, related, or unrelated birdsong. Results indicated that the original basic level never lost its privileged status. Expertise increased access to categorical information at the subordinate level for intermediate exports and at both the subordinate and sub-subordinate levels for advanced experts, causing these sublevels to function as basic. Throughout the continuum of expertise, conceptual knowledge interacted with perception. Accordingly, experts attended to different and more subtle perceptual features than novices.

Animals↗
PubMed1996

Immunocytochemical localization of growth factors and their receptors in human pre-embryos and Fallopian tubes.

We utilized indirect immunocytochemistry to demonstrate the presence of growth factors and their receptors in human pre-embryos and Fallopian tubes. In pre-embryos, only transforming growth factor-alpha (TGF-alpha) and the intracellular domain of epidermal growth factor receptor (EGFR) were found at the 4-cell stage. In 8- to 14-cell pre-embryos, TGF-alpha, the intracellular and extracellular domains of EGFR, and insulin-like growth factor-I and its receptor were found. Antibodies against TGF-alpha stained all Fallopian tube specimens, while the extracellular domains of EGFR was only found in specimens from patients with either blood type A or AB. These results suggest a cross-reactivity between the extracellular domain of the EGFR and blood group antigens. Our novel demonstration of growth factor receptor staining in human pre-embryos shows that growth factor receptor localization is dependent on the developmental stage of human pre-embryos. We have also established a potentially important link between the Fallopian tube which secretes growth factors and the localization of growth factor receptors in pre-embryos. These findings are compatible with the hypothesis that tubal secretions are embryotrophic for the early development of the pre-embryo.

Adult↗