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Biomedical subjects

G M Jensen

Publications and source records attributed to G M Jensen.

At least 19 recordsLinked to original sources
PubMed1992

Protein control of iron-sulfur cluster redox potentials.

The relationship between the three-dimensional structures of iron-sulfur proteins and the redox potentials of their iron-sulfur clusters is of fundamental importance. We report calculations of the redox potentials of the [Fe4S4(S-cys)4]-2/-3 couple in four crystallographically characterized proteins: Azotobacter vinelandii ferredoxin I, Peptococcus aerogenes ferredoxin, Bacillus thermoproteolyticus ferredoxin, and Chromatium vinosum high potential iron protein (HiPIP). Our calculations use the "protein dipoles Langevin dipoles" microscopic electrostatic model, which includes both protein and solvent water. The variations in calculated redox potentials are in excellent agreement with experimental data. In particular, our results confirm the important role of amide groups close to the cluster in separating the potential of C. vinosum HiPIP from those of the other three proteins. However, the potentials of these latter exhibit a substantial range despite extremely similar amide group environments of their clusters. Our results show that the potentials in these proteins are tuned in part by varying the access of solvent water to the neighborhood of the cluster. Our calculations provide the first successful quantitative modeling of the protein control of iron-sulfur cluster redox potentials.

Azotobacter vinelandii↗
PubMed1992

Attribute dimensions that distinguish master and novice physical therapy clinicians in orthopedic settings.

The purpose of this qualitative case study was to further investigate the work of master and novice clinicians within the practice setting. The sample consisted of three master clinicians and three novice clinicians practicing in orthopedic outpatient physical therapy settings in three different regions of the United States. Data collection by three researchers included observation of each clinician treating at least three patients, audiotaping of all treatment sessions, interviews with clinicians and patients, and a review of patient records. Analysis of the data within and across cases revealed five attribute dimensions that distinguished the master clinician from the novice clinician. One attribute dimension (ie, confidence in predicting patient outcomes) related to knowledge, and four attribute dimensions (ie, ability to control the environment, evaluation and use of patient illness and disease data, focus of verbal and nonverbal communication with patients, and importance of teaching to hands-on care) related to improvisational performance. Further investigations are needed to confirm these findings and add to the body of knowledge concerning the parameters of physical therapy that may affect the efficacy and quality of patient care.

Communication↗
PubMed1992

Manual therapy: a critical assessment of role in the profession of physical therapy.

Interest in manual therapy appears to continue to grow among physical therapy clinicians and educators throughout the world even though the underlying concepts and techniques have not been justified by a knowledge base. The purposes of this article are to critically assess the role of manual therapy within the physical therapy profession and to provide an introduction to the other articles in this special issue. Eisner's model of explicit, implicit, and null curricula is used as a framework for our analysis and our discussion of manual therapy. The explicit area of manual therapy includes discussions of the definition and the role of manual therapy, the scientific rationale for manual therapy, and manual therapy in education and a comparison of manual therapy evaluative frameworks. The implicit area deals with the role of clinical decision making and critical thinking in manual therapy in education and rehabilitation. In the null (unaddressed) area of manual therapy, we suggest directions for future development and research.

Clinical Competence↗
PubMed1991

Site-directed mutagenesis of Azotobacter vinelandii ferredoxin I. Changes in [4Fe-4S] cluster reduction potential and reactivity.

We have used site-directed mutagenesis to obtain two variants of Azotobacter vinelandii ferredoxin I (AvFdI), whose x-ray structures are now available. In the C20A protein, a ligand to the [4Fe-4S] cluster was removed whereas in the C24A mutant a free cysteine next to that cluster was removed. Like native FdI, both mutants contain one [4Fe-4S] cluster and one [3Fe-4S] cluster. The structure of C24A is very similar to that of native FdI, while the structure of C20A is rearranged in the region of the [4Fe-4S] cluster to allow it to use the free Cys-24 as a replacement ligand. Here we compare the properties of the native, C20A, and C24A proteins. Although all three proteins are O2 stable in vitro, the C20A protein is much less stable toward proteolysis than the other two in vivo. Spectroscopic results show that all three proteins exhibit the same general redox behavior during O2-oxidation and dithionite reduction. Electrochemical data show that the [3Fe-4S] clusters in all three proteins have the same pH-dependent reduction potentials (-425 mV versus SHE, pH 7.8), whereas the [4Fe-4S] cluster potentials vary over a approximately 150 mV range from -600 mV (C24A) to -647 mV (native) to -746 mV (C20A). Despite this variation in potential both the C20A and C24A proteins appear to be functional in vivo. Native FdI reacts with three equivalents of Fe(CN)3-(6) to form a paramagnetic species previously proposed to be a cysteinyl-disulfide radical. Neither the C20A nor the C24A variant undergoes this reaction, strongly suggesting that it involves the free Cys-24.

Amino Acid Sequence↗
PubMed1991

Circular dichroism and magnetic circular dichroism of Azotobacter vinelandii ferredoxin I.

Room temperature circular dichroism (CD) and low temperature magnetic circular dichroism (MCD) spectra of air-oxidized and dithionite-reduced Azotobacter vinelandii ferredoxin I (FdI), a [( 4Fe-4S]2+/1+, [3Fe-4S]1+/0) protein, are reported. Unlike the CD of oxidized FdI, the CD of dithionite-reduced FdI exhibits significant pH dependence, consistent with protonation-deprotonation at or near the cluster reduced: the [3Fe-4S] cluster. The MCD of reduced FdI, which originates in the paramagnetic reduced [3Fe-4S]0 cluster, is also pH-dependent. Detailed studies of the field dependence and temperature dependence of the MCD of oxidized and reduced FdI, in the latter case at pH 6.0 and 8.3, are reported. The low-field temperature dependence of the MCD of oxidized FdI, which originates in the paramagnetic oxidized [3Fe-4S]1+ cluster, establishes the absence of a significant population of excited electronic states of this cluster up to 60 K. The low-field temperature dependence of the MCD of reduced FdI establishes that the ground-state manifold of the reduced [3Fe-4S]0 cluster possesses S greater than or equal to 2 at both pH 6.0 and 8.3. Analysis, assuming S = 2 and an axial zero-field splitting Hamiltonian, leads to D = -2.0 and -3.5 cm-1 at pH 6.0 and 8.3, respectively. The site of the (de)protonation affecting the spectroscopic properties of the [3Fe-4S] cluster remains unknown.

Azotobacter↗
PubMed1991

Perspectives on gender and professional issues among female physical therapists.

The purposes of this study were to identify gender-related values, perceptions, and experiences of female physical therapists as these factors relate to female physical therapists' professional development and to offer an initial critique of the identified elements in comparison with a traditional model of professionalism. In-depth interviews were conducted with 10 physical therapists in two different states by the primary investigator. The interviews were analyzed utilizing qualitative data-analysis techniques, and a conceptual framework was developed from the literature and the interviews. Three major thematic categories were identified: (1) values, comprising the subcomponents of caring, relationship, empowerment, and context; (2) family role, comprising the subcomponents of enhancements, limitations, and coping strategies; and (3) sexism, comprising the subcomponents of leadership, money, and respect. These findings provide an initial basis for understanding more about factors that may both limit and enhance female physical therapists' professional development.

Adaptation, Psychological↗
PubMed1990

Landmarking of cephalograms using a microcomputer system.

Landmarks, or certain characteristic reference points, on cephalograms are used as a diagnostic aid employed in treatment planning by orthodontists. This work presents an algorithm for recognizing some anatomical features and locating landmarks on lateral skull X rays (cephalograms) using digital image processing and feature recognition techniques. A cephalogram is digitized and stored in a computer memory. Prefiltering is applied to remove image noise. The bony and flesh profiles of jaw and front face are traced. Using these profiles the algorithm locates 17 points on the image, some on bony features and others on soft tissue. To locate these points, edge-enhancement, thresholding, and edge-detection techniques are applied. The algorithm can be run on an IBM compatible microcomputer.

Algorithms↗
PubMed1990

Site-directed mutagenesis of Azotobacter vinelandii ferredoxin I: [Fe-S] cluster-driven protein rearrangement.

Azotobacter vinelandii ferredoxin I is a small protein that contains one [4Fe-4S] cluster and one [3Fe-4S] cluster. Recently the x-ray crystal structure has been redetermined and the fdxA gene, which encodes the protein, has been cloned and sequenced. Here we report the site-directed mutation of Cys-20, which is a ligand of the [4Fe-4S] cluster in the native protein, to alanine and the characterization of the protein product by x-ray crystallographic and spectroscopic methods. The data show that the mutant protein again contains one [4Fe-4S] cluster and one [3Fe-4S] cluster. The new [4Fe-4S] cluster obtains its fourth ligand from Cys-24, a free cysteine in the native structure. The formation of this [4Fe-4S] cluster drives rearrangement of the protein structure.

Azotobacter↗
PubMed1990

The novice versus the experienced clinician: insights into the work of the physical therapist.

The purpose of this study was to develop a conceptual framework and a data-collection tool to begin a systematic analysis of the work of the physical therapist. The primary method of data collection was nonparticipant observation of physical therapist-patient treatment sessions. A team of two researchers performed each of the observations. Eight physical therapists, representing three levels of experience, were observed in four different adult outpatient orthopedic settings. Field notes constructed from the observations and transcribed data were used to develop coding categories. These categories were the basis for the development of five themes that describe some aspects of the therapeutic intervention: 1) how treatment time is allocated, 2) the types and uses of information gathered from the patient, 3) the impact of the therapeutic environment, 4) the degree of responsive therapeutic interaction, and 5) the therapist integration of nontherapeutic interaction with therapeutic interaction. These findings are a beginning for understanding the practice of physical therapy.

Clinical Competence↗
PubMed1990

Physical therapist curricula for the 1990s: educating the reflective practitioner.

This article discusses why many current physical therapy entry-level programs may not be designed to educate the type of physical therapy practitioner needed for the 1990s. We suggest a framework for analyzing curriculum content to determine how the curriculum is influencing student outcomes. This framework includes three reference points of analysis, as suggested by Eisner's model of implicit, explicit, and null curricula. We also describe a new kind of physical therapy practitioner, the "reflective practitioner" (Schon's model), and suggest how various curricular components can support the development of this type of practitioner.

Curriculum↗
PubMed1989

The axial ligands of heme in cytochromes: a near-infrared magnetic circular dichroism study of yeast cytochromes c, c1, and b and spinach cytochrome f.

Room temperature near-infrared magnetic circular dichroism and low-temperature electron paramagnetic resonance measurements have been used to characterize the ligands of the heme iron in mitochondrial cytochromes c, c1, and b and in cytochrome f of the photosynthetic electron transport chain. The MCD data show that methionine is the sixth ligand of the heme of oxidized yeast cytochrome c1; the identify of this residue is inferred to be the single conserved methionine identified from a partial alignment of the available cytochrome c1 amino acid sequences. A different residue, which is most likely lysine, is the sixth heme ligand in oxidized spinach cytochrome f. The data for oxidized yeast cytochrome b are consistent with bis-histidine coordination of both hemes although the possibility that one of the hemes is ligated by histidine and lysine cannot be rigorously excluded. The neutral and alkaline forms of oxidized yeast cytochrome c have spectroscopic properties very similar to those of the horse heart proteins, and thus, by analogy, the sixth ligands are methionine and lysine, respectively.

Amino Acid Sequence↗
PubMed1989

Qualitative methods in physical therapy research: a form of disciplined inquiry.

Qualitative research methods have special relevance for physical therapy. Qualitative methods provide researchers with the tools to examine social settings and human behavior. The methods are well suited to studying the complex, multidimensional environments present in physical therapy practice and education. A thorough understanding of research methodology is a necessary prerequisite for disciplined research. This article presents an overview of the philosophy underlying qualitative research, a discussion of the application of qualitative methods, and a brief analysis of how to address reliability and validity concerns in qualitative research. Increased understanding of what qualitative research is and how it can be done should promote disciplined qualitative research in physical therapy.

Interviews as Topic↗
PubMed1988

The work of accreditation on-site evaluators. Enhancing the development of a profession.

The purpose of this study was to explore the work of on-site evaluators in the physical therapy accreditation process. Specifically, this research investigated how the accreditation on-site visit may serve as a method for defining the dominant values of a developing profession. A set of criteria selected from the literature describing the process of professionalization served as an operational model of professional values for the study. The model served as the framework for analysis and categorization of the professional values that evaluators emphasized during the on-site visits. The qualitative data collection methods of interview, nonparticipant observation, and document analysis were used in constructing case studies of five physical therapy education program accreditation visits. Results of this research indicated that on-site evaluators represent an elite community within the field and share similar values about the profession. These shared values about the professionalization of physical therapy formed the basis for evaluators' interpretation of accreditation standards. Evaluators' emphasis on the professional values that focus on defining and validating the body of knowledge in physical therapy and faculty endorsement of the norms of the academic work place have implications for the continued professionalization of physical therapy.

Accreditation↗
PubMed1987

Changes in spinal mobility with increasing age in women.

The purpose of our study was to determine changes in spinal mobility for women aged 20 to 84 years. Anterior flexion, right and left lateral flexion, and extension were measured on 109 healthy women. The modified Schober method was used to measure anterior flexion. Standard goniometry was used to measure lateral flexion and extension. The results of the study indicated that spinal mobility decreases with advancing age. The most significant (p less than .05) differences occurred between the two youngest and the two oldest age categories. Data gathered in this study indicate that physical therapists should consider the effects of age on spinal mobility when assessing spinal range of motion. A simple, objective method for measuring spinal mobility is presented. Suggestions for future research are given.

Adult↗
PubMed1985

Correction of dentofacial deformities in children and adolescent patients.

Modern orthognathic surgical techniques can complement orthodontic treatment of children and adolescent patients. A wide variety of deformities can be surgically corrected at a young age and examples selected from more than 100 treated pediatric patients are presented. As with all surgical procedures, the risks of surgery and anesthesia must be weighed against the benefits which are expected to result from the outcome of the surgery.

Adult↗
PubMed1985

Incidence of work-related low back pain in physical therapists.

The purpose of this study was to determine the incidence of work-related low back pain (LBP) in physical therapists and to identify common characteristics of therapists who reported work-related LBP. Questionnaires were mailed to a random sample of 500 registered physical therapists. Of the 344 (69%) questionnaires returned, 29 percent reported work-related LBP. The initial onset most frequently occurred between the ages of 21 and 30 years and within the first four years of experience as a physical therapist. Eighty-three percent of the therapists first incurred work-related LBP during treatment of patients, primarily in acute care and rehabilitation facilities. "Lifting with sudden maximal effort" and "bending and twisting" were frequent mechanisms of injury. Further research is necessary to investigate the effect work-related LBP has on productivity and quality of patient care within facilities and to identify preventive measures to decrease the incidence of work-related LBP.

Adult↗
PubMed1979

Horizontal postrotatory nystagmus response in female subjects with adolescent idiopathic scoliosis.

Quantitative and qualitative assessment of vestibular function was made in 18 female subjects with adolescent idiopathic scoliosis and a control group of 25 female subjects without scoliosis. The Southern California Postrotary Nystagmus Test, which examines postrotatory nystagmus response, was used to assess the vestibular function of subjects in both groups. The results indicated that subjects with adolescent idiopathic scoliosis had a significantly decreased duration of postrotatory nystagmus as well as irregularities in nystagmus form. The recommendation was made that a neurological examination, including assessment of vestibular function, be incorporated into screening methods for scoliosis.

Adolescent↗