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Biomedical subjects

M J Price

Publications and source records attributed to M J Price.

At least 19 recordsLinked to original sources
PubMed1992

Purification and analysis of proteinase-resistant mutants of recombinant platelet-derived growth factor-BB exhibiting improved biological activity.

Recombinant platelet-derived growth factor (PDGF)-BB was expressed and secreted from yeast in order to study the structure-function relationships of this mitogen. A simple purification scheme has been developed which yields greater than 95% pure PDGF-BB. Analysis of this recombinant PDGF-BB shows partial proteolysis after arginine-32. Substitution of this arginine residue, or arginine-28 [a potential KEX2 (lysine-arginine endopeptidase) cleavage site], prevents or reduces cleavage of PDGF-BB respectively. These mutations result in a 5-fold increase in expression levels of PDGF-BB, and the resulting mutant proteins show higher activity in a number of biological assays than the cleaved wildtype PDGF-BB. These data are in accord with previous work by Giese, LaRochelle, May-Siroff, Robbins & Aaronson [(1990) Mol. Cell Biol. 10, 5496-5501] suggesting that the region isoleucine-25-phenylalanine-37 is involved in PDGF-receptor binding.

3T3 Cells↗
PubMed1992

Characterization of the structure and conformation of platelet-derived growth factor-BB (PDGF-BB) and proteinase-resistant mutants of PDGF-BB expressed in Saccharomyces cerevisiae.

A detailed biophysical study of the secondary and tertiary structures of recombinant platelet-derived growth factor (PDGF)-BB produced in yeast has been carried out. The secondary structure of the molecule is composed of 54% beta-sheet with less than 5% ordered helix. The single tryptophan residue has been shown to be solvent-accessible; however, the ability of the side chain to rotate is severely restricted. The fluorescence emission is quenched at pH 7.0 and in the presence of high salt, but dequenched by titration to lower pH with a pK of 5.8. Two proteinase-resistant mutants of PDGF [( Ser28]- and [Pro32]-PDGF-BB) have also been characterized and shown to have secondary and tertiary structures indistinguishable from wild-type PDGF-BB. These are, therefore, suitable stable background molecules in which to carry out structure-activity-relationship studies on PDGF-BB.

Mutagenesis, Site-Directed↗
PubMed1992

Abnormalities in color vision and contrast sensitivity in Parkinson's disease.

Dopamine is a neurotransmitter found in the retina. Delays in the visual evoked responses and abnormalities in contrast sensitivity occur in patients with Parkinson's disease. Improvement in the P100 has followed L-dopa therapy. Suspected abnormalities at the retinal level in Parkinson's disease are observed in reductions in photopic, scotopic, and pattern-derived electroretinograms. We studied 35 patients with Parkinson's disease and 26 controls of comparable age and visual acuities using visual evoked responses, color vision, and contrast sensitivity testing. Contrast sensitivity thresholds were significantly different at most frequencies tested, using both stationary and temporally modulated sinusoidal gratings. The total error score of the Farnsworth-Munsell 100 Hue Test revealed significant differences between the patients and controls. The contrast thresholds derived from certain spatial frequencies and the total error in color score were significantly related to the duration of disease. A stepwise discriminant analysis correctly identified 94% of the patients and 94% of the controls. The significant error in chromatic discrimination observed in Parkinson's disease patients may be due to altered intraretinal dopaminergic synaptic activity in these patients.

Color Perception↗
PubMed1992

Developing national guidelines for nurse practitioner education: an overview of the product and the process.

In 1988, the National Organization of Nurse Practitioner Faculties appointed an ad hoc education committee (AHEC) to review existing nurse practitioner (NP) education curricula and to formulate national guidelines. An overview of the new NP guidelines are presented along with the philosophy, content, objectives, and competencies that are viewed as the foundation for NP education today. The guidelines are presented within the structure outlined in Brykczynski's (1985) research about NP practice. Thus, as a "product" of the Advanced Nursing Practice: Nurse Practitioner Curriculum Guidelines (NPCG), a new NP graduate for the 1990s could be described as one who demonstrates beginning competencies in primary health care theory and research within the five domains of practice identified by Brykczynski.

Clinical Competence↗
PubMed1991

Secretion of human epidermal growth factor from Saccharomyces cerevisiae using synthetic leader sequences.

We have investigated different leader sequences for their ability to direct the efficient secretion of human epidermal growth factor (hEGF) from Saccharomyces cerevisiae. We designed a consensus signal sequence which directs secretion of hEGF from yeast as efficiently as the yeast invertase signal sequence. However, secretion is increased over fivefold by the introduction, after the signal sequence, of a synthetic 19-amino acid (aa) pro-sequence containing a cleavage recognition site for the KEX2 protease. Even in the absence of an Asn-linked glycosylation site, secretion of hEGF using the synthetic prepro-leader was as efficient as that directed by the alpha-factor leader. The role of the KEX2 protease cleavage site was investigated by mutation of the yeast alpha-factor KEX2 site (cleavage after Lys-Arg). Cleavage was obtained with the following order of efficiency, Lys-Arg greater than Pro-Arg greater than Asp-Arg, although the sequence context was also found to affect efficiency.

Amino Acid Sequence↗
PubMed1989

Ferrochelatase activity in Azospirillum brasilense with reference to the influence of metal cations.

Ferrochelatase in membrane preparations from Azospirillum brasilense displayed an activity of 2.17 mumol protoheme formed.h-1.mg protein-1 which is 10-fold greater than previous reports for other bacteria. This ferrochelatase showed an apparent Km of 20.9 microM for Fe2+, a pH optimum of 6.0-6.5, and stimulation by oleic or stearic acids. Co2+, Cu2+ and Zn2+ inhibited the incorporation of Fe2+ into protoporphyrin IX while Ni2+ and Mg2+ had no effect on protoheme synthesis. Activity with Fe2+ and mesoporphyrin IX was less than with protoporphyrin IX but deuteroporphyrin IX produced the highest rate of protoheme synthesis. The membrane fraction containing ferrochelatase activity was found to insert Cu2+, Ni2+, Zn2+ and Co2+ enzymatically into protoporphyrin IX to produce metalloporphyrins. Cu2+ incorporation into protoporphyrin IX proceeded at a rate greater than with Fe2+ and the Km for Cu2+ was 21.9 microM.

Azospirillum brasilense↗
PubMed1988

The pattern electroretinogram and visual-evoked potential in glaucoma.

The pattern electroretinogram (PERG) may reflect ganglion cell or inner retinal layer activity. The most sensitive spatial and temporal variables for testing patients with glaucoma have not yet been identified. Fifty-two glaucoma suspects, 51 glaucoma patients, and 28 normal subjects were studied with the PERG and VEP, using three repetition rates and three spatial frequencies. Fast Fourier transforms were calculated at each spatial frequency and reversal rate. An analysis of variance revealed that normals could be differentiated from ocular hypertension and glaucoma patients using the amplitude of the PERG (second and fourth harmonic). Abnormalities in phase of the PERG between groups were also detected. A discriminant analysis of all amplitude and phase data revealed that the phase shift of the response of the second harmonic at 11 alternations/s (15-min checks) and at 5.5 alternations/s (15-min checks) correctly identified 81% of the normal and 75% of the glaucoma patients. The phase shift determinations of the VEP revealed significant abnormalities using 2 and 1/2 standard deviation confidence limits. There was significant overlap in the pattern ERG amplitude and phase shift in all three groups.

Analysis of Variance↗
PubMed1988

Strategies and conditions for teaching theoretical nursing: an international perspective.

How, when, and why to teach nursing theory are still central questions for nurse educators. The questions are restated and generalized to the whys, and hows, and the whens to incorporate theoretical nursing rather than nursing theory in nursing education. Process and strategies for teaching theoretical nursing are compared and contrasted with those related to research. We propose the use of similar strategies and add several essential conditions related to theoretical nursing. In teaching theoretical nursing, educators are expected to develop an environment that values theory and ways by which a theoretical identity is facilitated and fostered in students. Critical and reflective thinking as well as the role modelling of local models of excellence are central ingredients in the development of nurses who are committed to using and developing theories. One approach in incorporating theory in curricula is to identify central components and goals such as historical analyses, domain boundaries, theory utilization, process and strategies for theory development and testing. Once components are identified, faculty can make a decision about where to incorporate them. We have proposed several approaches that incorporate theoretical nursing in undergraduate and graduate programmes.

Curriculum↗
PubMed1985

Pupillary constriction to darkness.

Patients with congenital achromatopsia and congenital stationary night blindness have been known to show a transient pupillary constriction to darkness. We examined 50 normal subjects and 108 patients with retinal and optic nerve dysfunction to see if any had an initial pupillary constriction to darkness. We used a new infrared television apparatus. Four patients with congenital stationary night blindness, four with achromatopsia, two with bilateral optic neuritis, and one with dominant optic atrophy showed the phenomenon. In the patients who showed this unusual pupillary response to darkness it was the first observable event every time the lights were turned off. The constriction could usually be seen with a handlight, and it was similar in latency to the normal pupillary dilatation to darkness. Pupillary constriction to darkness is a clinically valuable sign that can be used in the detection of congenital retinal disease in children with poor vision.

Adolescent↗
PubMedDate not supplied

Use of hydroxyethyl starch to improve granulocyte collection in the Latham blood processor.

This report describes a practical, relatively inexpensive system of leukapheresis and plateletpheresis, utilizing the Haemonetics blood processor. The results of 236 phereses of normal donors are reported, with particular attention to an evaluation of five different anticoagulant mixtures: ACD, 2 per cent citrate in saline, and three different combinations of citrate and hydroxyethyl starch (HES). These mixtures were compared with respect to their effectiveness in the harvesting of granylocytes and platelets, respectively. The best harvest of granulocytes (3.5 X 10(9) cells per liter of blood processed) was with 6 per cent HES anticoagulated with trisodium citrate. All solutions gave about the same platelet yields (a mean of 1.6 X 10(11) per liter of blood processed). Because of its higher citrate content, ACD caused three times as many donor reactions as the other solutions. The use of HES thus permits this widely available plateletpheresis system to be used for leukapheresis with only minimal procedural modification.

Anticoagulants↗
PubMedDate not supplied

Leukapheresis of patients with chronic granulocytic leukemia (CGL), using the Haemonetics blood processor.

By the use of citrated hydroxyethyl starch (HES) as anticoagulant, the Haemonetics blood processor can be used to obtain large numbers of granulocytes from patients with CGL. This report is of 67 leukaphereses on 11 different patients. A median of 1.14 x 10(11) granulocytes was obtained per 6-cycle pheresis (3.4 x 10(10) per liter of blood processed), or eight to ten times the number obtained from comparable leukaphereses of normal donors. High yields of platelets were also obtained, although not in proportion to granulocytes, since some of the patients used as donors have normal or even low platelet counts. The patients tolerated the procedure well, and no adverse reactions to HES were observed. The patients experienced a mean 35 per cent drop in the postleukapheresis WBC count, but in no case was this drop sustained for more than a few days, and no lasting effect on the disease process was observed.

Adolescent↗
PubMedDate not supplied

Citrate anticoagulants for plateletpheresis.

In 112 plateletphereses done by the Haemonetics blood processor, the comparative effectiveness of ACD formula A, ACD formula B, and 2 per cent citrate in saline was evaluated. With respect to yields of platelets and white blood cells (e.g., lymphocytes), ACD-B was significantly better than the other two. Both ACD-B and 2 per cent citrate gave a much lower incidence of citrate reactions in the donors than were encountered with ACD-A.

Anticoagulants↗
PubMedDate not supplied

Qualitative analysis of the patient-provider interactions: the patient's perspective.

This qualitative analysis of videotaped patient-provider interviews focuses attention on the patient's experience of diabetes. Excerpts from the videotaped interviews are examined from the framework of a diabetes management trajectory identified from a qualitative research study of 19 insulin-managed adults. It is suggested that providers need to become sensitive to the experience of illness-as-lived in order to more accurately assess patient responses to management and to promote sustained efforts toward diabetes self-care.

Diabetes Mellitus↗
PubMedDate not supplied

X-linked congenital stationary night blindness with myopia and nystagmus without clinical complaints of nyctalopia.

Seven of eight patients presented initially or were followed for decreased acuity and nystagmus without complaints of night blindness. The diagnosis of congenital stationary night blindness was established with electroretinogram and dark adaptation testing. Careful electrodiagnostic testing is needed to provide accurate genetic counseling. Two patients showed pupillary constriction to darkness which is a sign of retinal disease in young patients.

Adolescent↗
PubMedDate not supplied

Glaucoma screening.

The ability to screen for any disease is based on several factors (established natural history, high prevalence rates, effective treatment, and available screening tests); however, the earliest psychosocial, clinical, or electrodiagnostic changes in glaucoma are presently unknown. Public awareness of glaucoma must be increased. Mass screenings not only aid in the detection of disease, but through their promotion by the local media, they also assist in augmenting the general public's awareness of eye health. The future of more effective screening may lie in more objective or automated testing that could be performed by lesser trained personnel.

Glaucoma↗
PubMedDate not supplied

High-resolution computed tomography of the basilar artery: 1. Normal size and position.

Normal high-resolution computed tomographic (CT) scans of 126 patients were reviewed to define the diameter, height of the bifurcation, and transverse position of the normal basilar artery. The mean diameter of the normal basilar artery is 3.17 mm at the level of the pons. In 92% of normal subjects, the basilar bifurcation is located in the interpeduncular cistern adjacent to the dorsum sellae or in the suprasellar cistern below the level of the floor of the third ventricle. In 98% of normal individuals, the basilar artery courses in the midline or in a paramedian position, medial to the lateral margins of the clivus and dorsum sellae.

Adolescent↗