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Biomedical subjects

B King

Publications and source records attributed to B King.

At least 73 records · Page 4Linked to original sources
PubMed1996

Mg coordination by amino acid side chains is not required for assembly and function of the special pair in bacterial photosynthetic reaction centers.

A conserved histidine serves as the axial ligand to the Mg of bacteriochlorophylls in the photosynthetic reaction center (RC) and many other photosynthetic systems. The histidine axial ligands to each and both bacteriochlorophylls of the special-pair primary electron donor of the Rhodobacter sphaeroides RC have been replaced with glycine to create a cavity. In each case, RCs assemble and a normal special-pair comprised of Mg-containing bacteriochlorophylls is formed, as judged by many different spectroscopic and functional probes (e.g., absorption and Stark spectra, *P decay kinetics, P+Q(A)- recombination rate, and the redox potential of P). In contrast with heme proteins, where this strategy has been exploited to introduce exogenous organic ligands that can greatly affect the functional properties of the protein [DePillis, G. D., Decatur, S. M., Barrick, D., & Boxer, S. G. (1994) J. Am. Chem. Soc. 116, 6981-6982], addition of exogenous imidazole, pyridine, and ethanethiol has no measurable effect on the functional properties of the special pair in these cavity mutants. FT-Raman spectroscopy is used to provide more detailed information on local interactions around the special pair. Data in the core-size marker mode and carbonyl stretching region suggest that an adventitious ligand replaces histidine as the axial ligand to bacteriochlorophylls in the cavity mutants. We speculate that this ligand is water. Furthermore, the position of the core-size marker mode changes when the cavity mutant RCs are incubated with exogenous ligands such as imidazole, pyridine, or ethanethiol, suggesting that the axial ligand to the special pair BChls can be exchanged in the cavity mutants. Interestingly the temperature dependence of P+Q(A)- recombination kinetics is very similar in the cavity mutants and WT, suggesting that the axial ligands to the special pair are not significant contributors to the solvent reorganization energy for this reaction. These results lead to the surprising conclusion that the nature of the axial ligand to the special pair has little influence on the properties of the macrocycle, and that axial coordination from the protein by histidine is not required for bacteriochlorophyll binding or for efficient electron transfer in the RC.

Amino Acids↗
PubMed1996

Fast spin echo magnetic resonance imaging: clinical application in screening for acoustic neuroma.

The advent of magnetic resonance imaging has greatly improved our ability to diagnose acoustic tumors, but it is a relatively expensive imaging modality. In the present climate of medical cost restraints, methods that reduce costs but maintain quality are extremely desirable. We report a new magnetic resonance imaging technique that uses fast spin echo without gadolinium. It provides ultrahigh-resolution images of the internal auditory canal and cerebellopontine angle. The sensitivity of this technique for the detection of acoustic tumors is equivalent to conventional gadolinium-enhanced magnetic resonance imaging, but the global cost is comparable with that of brain stem audiometry. In our practice fast spin echo magnetic resonance imaging has replaced brain stem audiometry as a screening modality to evaluate most acoustic tumor suspects. Also, the intricate detail of the internal auditory canal anatomy provided by this technique is useful in planning surgical removal of acoustic tumors.

Adult↗
PubMed1996

A reliability and validity study of the McMaster Quality of Life Scale (MQLS) for a palliative population.

The McMaster Quality of Life Scale (MQLS) was developed to measure the quality of life in a palliative patient population. This paper describes the tool and its psychometric properties. Palliative stage patients could assess their condition using this tool (r = 0.84; 95% Cl 0.76-0.94). Although ratings by different raters (patient, family, staff) were correlated, systematic differences were found by source of rating, which suggests that proxy rating (substituting family or staff ratings for a patient rating) should be avoided. The MQLS was sensitive to changes in the patient's quality of life. Neither age nor sex of patient influenced total score obtained. Persons close to death rated their quality of life as being poorer than those who were alive at the end of the data collection period. People who needed to have the MQLS read to them rated their quality of life somewhat lower than patients who could complete the task by themselves. Staff-rated MQLS scores correlated significantly with the staff-rated Spitzer Quality of Life Index. This study suggests the MQLS is a reliable and valid measure of quality of life during the palliative phase.

Adult↗
PubMed1996

Low-cost high-resolution fast spin-echo MR of acoustic schwannoma: an alternative to enhanced conventional spin-echo MR?

PURPOSE: To determine whether unenhanced high-resolution T2-weighted fast spin-echo MR imaging provides an acceptable and less expensive alternative to contrast-enhanced conventional T1-weighted spin-echo MR techniques in the diagnosis of acoustic schwannoma. METHODS: We reviewed in a blinded fashion the records of 25 patients with pathologically documented acoustic schwannoma and of 25 control subjects, all of whom had undergone both enhanced conventional spin-echo MR imaging and unenhanced fast spin-echo MR imaging of the cerebellopontine angle/internal auditory canal region. The patients were imaged with the use of a quadrature head receiver coil for the conventional spin-echo sequences and dual 3-inch phased-array receiver coils for the fast spin-echo sequences. RESULTS: The size of the acoustic schwannomas ranged from 2 to 40 mm in maximum dimension. The mean maximum diameter was 12 mm, and 12 neoplasms were less than 10 mm in diameter. Acoustic schwannoma was correctly diagnosed on 98% of the fast spin-echo images and on 100% of the enhanced conventional spin-echo images. Statistical analysis of the data using the kappa coefficient demonstrated agreement beyond chance between these two imaging techniques for the diagnosis of acoustic schwannoma. CONCLUSIONS: There is no statistically significant difference in the sensitivity and specificity of unenhanced high-resolution fast spin-echo imaging and enhance T1-weighted conventional spin-echo imaging in the detection of acoustic schwannoma. We believe that the unenhanced high-resolution fast spin-echo technique provides a cost-effective method for the diagnosis of acoustic schwannoma.

Adult↗
PubMed1995

Murine embryonic yolk sac cells promote in vitro proliferation of bone marrow high proliferative potential colony-forming cells.

To examine the influence of the hematopoietic microenvironment on hematopoietic cell proliferation and differentiation during the yolk sac phase of hematopoiesis, we have recently established cell lines from embryonic yolk sac visceral endoderm (YSE) and mesoderm (YSM). In the present experiments, we compared in vitro growth of adult murine bone marrow high proliferative potential colony-forming cells (HPP-CFC) in coculture with YSE- and YSM-derived or adult bone marrow stromal cell lines. Whereas both yolk sac-derived and adult stromal cell lines supported the proliferation of HPP-CFC during coculture, YSE- and YSM-derived cells stimulated a significant increase in total HPP-CFC compared with adult bone marrow stromal cell lines. Conditioned media from both YSE- and YSM-derived cell lines also stimulated the growth of HPP-CFC in vitro, but only in combination with exogenous recombinant hematopoietic growth factors. Although multiple hematopoietic growth factor mRNAs were detected in the yolk sac-derived cells by polymerase chain reaction, only macrophage colony-stimulating factor (M-CSF) activity was detected in conditioned media using an enzyme-linked immunosorbent assay. A neutralizing polyclonal antibody against M-CSF did not diminish the YSE- or YSM-derived cell line conditioned media promotion of HPP-CFC colony formation. These results suggest that murine yolk sac-derived cell lines produce a novel soluble factor(s) that recruits primitive bone marrow hematopoietic cells to grow in vitro in response to a combination of hematopoietic growth factors.

Animals↗
PubMed1995

Origins of childhood dental fear.

This study explored Rachman's theory of fear acquisition applied to fear of the dentist in a large sample of low income American primary school children. Children and their mother/guardians were interviewed or completed questionnaires in the home about fear acquisition and related concerns. A multivariate logistic regression model was evaluated in order to explore the relationship of direct conditioning and modeling variables to fear levels. Both direct conditioning and parent modeling factors were significant independent predictors of fear level even when controlling for gender, age and other sociodemographic and attitudinal factors.

Attitude to Health↗
PubMed1995

Reproducibility and observer variability of transrectal ultrasound measurements of prostatic volume.

Transrectal ultrasound (TRUS) is an established investigation in benign and malignant prostatic disease though the level of reproducibility of TRUS volume measurements is not known. A group of observers in the UK and the USA who were participating in linked prospective studies of benign prostatic hyperplasia each carried out measurements during real-time scanning and on a series of static TRUS images. Results demonstrated good reproducibility for measurements of antero-posterior, transverse, and longitudinal dimensions of the prostate by an experienced UK urologist; only a minor degree of interobserver variation occurred in measurements made between experienced UK and USA observers. Using static images, USA observers obtained results that were in good agreement, whereas the UK observers, only two of whom used TRUS regularly, were in poor agreement with each other. This study demonstrates a high level of reproducibility for TRUS volume measurements performed by experienced observers.

Adult↗
PubMed1995

Interval mammography after needle localization biopsy of breast abnormalities that are pathologically benign.

BACKGROUND: Needle localization biopsy is commonly performed for the diagnosis of mammographic abnormalities. Routine specimen radiography is generally recommended, but the value of routine short-interval postbiopsy mammography has not been analyzed. PATIENTS AND METHODS: We performed a retrospective review of 299 consecutive localized biopsies in 286 women from March 1989 to November 1993. Of these biopsies, 217 from the basis for this study; all yielded a benign pathologic diagnosis and had both specimen radiography and 3-month interval mammograms performed. RESULTS: A total of 192 (88%) of postbiopsy mammograms were interpreted as negative, while 22 (10%) were suspicious. Three patients had second biopsies and all had benign diagnoses, 16 had follow-up mammograms that were interpreted as normal or stable, and 3 patients were lost to follow-up. A suspicious postbiopsy mammogram had no significant relationship to initial mammographic abnormality or pathologic diagnosis, but did correlate with specimen radiograph interpretation (P = 0.02) by chi-square comparison). CONCLUSIONS: In a series of needle localization biopsies with intraoperative specimen radiography, postbiopsy mammography failed to reveal any missed cancers. Short-interval follow-up mammography is unnecessary to assess for residual abnormalities when specimen radiography confirms excision of the abnormality.

Biopsy, Needle↗
PubMed1994

The effect of directly observed therapy on the rates of drug resistance and relapse in tuberculosis.

BACKGROUND: Tuberculosis has reemerged as an important public health problem, and the frequency of drug resistance is increasing. A major reason for the development of resistant infections and relapse is poor compliance with medical regimens. In Tarrant County, Texas, we initiated a program of universal directly observed treatment for tuberculosis. We report the effect of the program on the rates of primary and acquired drug resistance and relapse among patients with tuberculosis. METHODS: We collected information on all patients with positive cultures for Mycobacterium tuberculosis in Tarrant County from January 1, 1980, through December 31, 1992. Through October 1986, patients received a traditional, unsupervised drug regimen. Beginning in November 1986, nearly all patients received therapy under direct observation by health care personnel. RESULTS: A total of 407 episodes in which patients received traditional treatment for tuberculosis (January 1980 through October 1986) were compared with 581 episodes in which therapy was directly observed (November 1986 through December 1992). Despite higher rates of intravenous drug use and homelessness and an increasing rate of tuberculosis during this 13-year period, the frequency of primary drug resistance decreased from 13.0 percent to 6.7 percent (P < 0.001) after the institution of direct observation of therapy, and the frequency of acquired resistance declined from 14.0 percent to 2.1 percent (P < 0.001). The relapse rate decreased from 20.9 percent to 5.5 percent (P < 0.001), and the number of relapses with multidrug-resistant organisms decreased from 25 to 5 (P < 0.001). CONCLUSIONS: The administration of therapy for M. tuberculosis infection under direct observation leads to significant reductions in the frequency of primary drug resistance, acquired drug resistance, and relapse.

Adolescent↗
PubMed1994

Saturable efflux of the peptides RC-160 and Tyr-MIF-1 by different parts of the blood-brain barrier.

Peptides have been shown to be transported in the direction of both blood to brain and brain to blood. Although blood to brain transport is known to occur at both the choroid plexus and the capillary bed of the brain, comprising the two major components of the blood-brain barrier, the location of efflux systems for peptides remains largely unstudied. We adapted established methodologies to study this question for two peptides known to be transported out of the brain after injection into the cerebrospinal fluid (CSF): Tyr-MIF-1, transported by peptide transport system (PTS)-1 and RC-160, a somatostatin analog transported by PTS-5. Radioactive iodide, known to be transported out of the brain primarily by the capillaries, also was studied. We found that after injection into brain tissue, RC-160 and iodide were rapidly transported out of the brain by saturable mechanisms. By contrast, efflux of Tyr-MIF-1 was slow and nonsaturable after injection into brain tissue, but rapid and saturable after injection into the lateral ventricle of the brain. Autoradiography confirmed that peptide injected into brain tissue did not diffuse far from the site of injection during the study period. The results indicate that the efflux system for RC-160 is located at least partly at the capillaries and suggest that the major location for the efflux system of Tyr-MIF-1 is at the choroid plexus.

Analgesics↗
PubMed1994

Bovine pulmonary blastomas: histomorphologic description and immunohistochemistry.

Three adult female dairy cattle with pulmonary blastomas were evaluated. The gross lesions at postmortem were described as multiple white circumscribed masses throughout the lungs, with pleural involvement in one cow and lymph node metastasis in the other two cows. Histologically, the tumors contained a dual population of mesenchymal and epithelial neoplastic cells. Epithelial cells formed nests, tubules, and formations resembling bronchioles of normal lung. Mesenchymal cells were spindle shaped with oval nuclei and fibrillar eosinophilic cytoplasm, were large rounded cells with multiple round nuclei and granular eosinophilic cytoplasm, or appeared blast-like, with large hyperchromatic nuclei and amphophilic cytoplasm. The tumors varied greatly in appearance from one field to another within the same tumor. Epithelial cells stained positively with anticytokeratin antibodies. Some spindle-shaped mesenchymal cells exhibited smooth muscle cell differentiation with positive staining with anti-vimentin, anti-muscle-specific actin, and anti-smooth muscle actin antibodies, whereas other rounded mesenchymal cells expressed striated muscle cell differentiation with multiple nuclei and positivity to anti-neuron-specific enolase and anti-muscle-specific actin antibodies. The variable expression of the intermediate filaments and cytoplasmic enzymes indicates multiple pathways of differentiation in the pulmonary blastomas.

Animals↗