Liposomal amphotericin B-the past.

The discovery of amphotericin B, a polyene antifungal compound, in the 1950s, and the formulation of this compound in a liposomal drug delivery system, has resulted in decades of use in systemic fungal infections. The use of liposomal amphotericin B formulation is referenced in many international guidelines for the treatment of fungal infections such as Aspergillus and cryptococcal disease and Candida infections, as well as other less common infections such as visceral leishmaniasis. With the development of liposomal amphotericin B, an improved therapeutic index could be achieved that allowed the attainment of higher drug concentrations in both the plasma and tissue while simultaneously lowering the toxicity compared with amphotericin B deoxycholate. In over 30 years of experience with this drug, a vast amount of information has been collected on preclinical and clinical efficacy against a wide variety of pathogens, as well as evidence on its toxicity. This article explores the history and nature of the liposomal formulation, the key clinical studies that developed the pharmacokinetic, safety and efficacy profile of the liposomal formulation, and the available microbiological data.

Tissue pharmacokinetics and pharmacodynamics of AmBisome® (L-AmBis) in uninfected and infected animals and their effects on dosing regimens.

By selecting a unique combination of lipids and amphotericin B, the liposome composition for AmBisome® (L-AmBis) has been optimized resulting in a formulation that is minimally toxic, targets to fungal cell walls, and distributes into and remains for days to weeks in various host tissues at drug levels above the MIC for many fungi. Procedures have been standardized to ensure that large scale production of the drug retains the drug's low toxicity profile, favorable pharmacokinetics and antifungal efficacy. Tissue accumulation and clearance with single or multiple intravenous administration is similar in uninfected and infected animal species, with tissue accumulation being dose-dependent and the liver and spleen retaining the most drug. The efficacy in animals appears to be correlated with drug tissue levels although the amount needed in a given organ varies depending upon the type of infection. The long-term tissue retention of bioactive L-AmBis in different organs suggests that for some indications, prophylactic and intermittent drug dosing would be efficacious reducing the cost and possible toxic side-effects. In addition, preliminary preclinical studies using non-intravenous routes of delivery, such as aerosolized L-AmBis, catheter lock therapy, and intravitreal administration, suggest that alternative routes could possibly provide additional therapeutic applications for this antifungal drug.

Toxicity and efficacy differences between liposomal amphotericin B formulations in uninfected and Aspergillus fumigatus infected mice.

Because of the reduced toxicity associated with liposomal amphotericin B preparations, different amphotericin B liposome products have been made. In the present study, we compared the amphotericin B liposomal formulations, AmBisome(®) (AmBi) and Lambin(®) (Lbn), in uninfected and Aspergillus fumigatus infected mice, using several in vitro and in vivo toxicity and efficacy assays. The results showed that the formulations were significantly different, with Lbn 1.6-fold larger than AmBi. Lbn was also more toxic than AmBi based on the RBC potassium release assay and intravenous dosing in uninfected mice given a single 50 mg/kg dose (80% mortality for Lbn vs. 0% for AmBi). Renal tubular changes after intravenous daily dosing for 14 days were seen in uninfected mice given 5 mg/kg Lbn but not with AmBi. Survival following A. fumigatus challenge was 30% for 10 mg/kg Lbn and 60% for 10 mg/kg AmBi. When the BAL and lungs were collected 24 h after the second treatment, AmBi at 10 or 15 mg/kg or 15 mg/kg Lbn lowered the BAL fungal burden significantly vs. the controls (P ≤ 0.05), while there was no difference in lung fungal burden amongst the groups. In contrast, lung histopathology at this same early timepoint showed that AmBi was associated with markedly fewer fungal elements and less lung tissue damage than Lbn. In conclusion, given the differences in size, toxicity, and efficacy, AmBi and Lbn were not physically or functionally comparable, and these differences underscore the need for adequate testing when comparing amphotericin B liposome formulations.

Impact of Proximal and Distal Pocket Site-Directed Mutations on the Ferric/Ferrous Heme Redox Potential of Yeast Cytochrome-c-Peroxidase.

Cytochrome-c-peroxidase (CCP) contains a five-coordinate heme active site. The reduction potential for the ferric to ferrous couple in CCP is anomalously low and pH dependent (Eo = ~-180 mV vs. S.H.E. at pH 7). The contribution of the protein environment to the tuning of the redox potential of this couple is evaluated using site directed mutants of several amino acid residues in the environment of the heme. These include proximal pocket mutation to residues Asp-235, Trp-191, Phe-202 and His-175, distal pocket mutation to residues Trp-51, His-52, and Arg-48; and a heme edge mutation to Ala-147. Where unknown, the structural changes resulting from the amino acid substitution have been studied by X-ray crystallography. In most cases, ostensibly polar or charged residues are replaced by large hydrophobic groups or alternatively by Ala or Gly. These latter have been shown to generate large, solvent filled cavities. Reduction potentials are measured as a function of pH by spectroelectrochemistry. Starting with the X-ray derived structures of CCP and the mutants, or with predicted structures generated by Molecular Dynamics (MD), predictions of redox potential changes are modeled using the Protein Dipoles Langevin Dipoles (PDLD) method. These calculations serve to model an electrostatic assessment of the redox potential change with simplified assumptions about heme iron chemistry, with the balance of the experimentally observed shifts in redox potential being thence attributed to changes in the ligand set and heme coordination chemistry, and/or other changes in the structure not directly evident in the X-ray structures (e.g. ionization states, specific roles played by solvent species, or conformationally flexible portions of the protein). Agreement between theory and experiment is good for all mutant proteins with the exception of the mutation Arg 48 to Ala, and His 52 to Ala. In the former case, the influence of phosphate buffer is adduced to account for the discrepancy, and measurements made in a bis-tris propane/2-(N-morpholino)ethanesulfonic acid buffer system agree well with theory. For the latter case, an unknown structural element relevant to His-52, and/or solvent influence in the mutant akin to anion binding in the distal pocket (though lacking proof that it is) manifests in this mutant. The use of exogenous (sixth) ligands in dissecting the contributions to control of redox potential are also explored as a pathway for model building.

The role of aspartate-235 in the binding of cations to an artificial cavity at the radical site of cytochrome c peroxidase.

The activated state of cytochrome c peroxidase, compound ES, contains a cation radical on the Trp-191 side chain. We recently reported that replacing this tryptophan with glycine creates a buried cavity at the active site that contains ordered solvent and that will specifically bind substituted imidazoles in their protonated cationic forms (Fitzgerald MM, Churchill MJ, McRee DE, Goodin DB, 1994, Biochemistry 33:3807-3818). Proposals that a nearby carboxylate, Asp-235, and competing monovalent cations should modulate the affinity of the W191G cavity for ligand binding are addressed in this study. Competitive binding titrations of the imidazolium ion to W191G as a function of [K+] show that potassium competes weakly with the binding of imidazoles. The dissociation constant observed for potassium binding (18 mM) is more than 3,000-fold higher than that for 1,2-dimethylimidazole (5.5 microM) in the absence of competing cations. Significantly, the W191G-D235N double mutant shows no evidence for binding imidazoles in their cationic or neutral forms, even though the structure of the cavity remains largely unperturbed by replacement of the carboxylate. Refined crystallographic B-values of solvent positions indicate that the weakly bound potassium in W191G is significantly depopulated in the double mutant. These results demonstrate that the buried negative charge of Asp-235 is an essential feature of the cation binding determinant and indicate that this carboxylate plays a critical role in stabilizing the formation of the Trp-191 radical cation.

Secretory pathways in Salmonella Typhimurium-induced fluid accumulation in the porcine small intestine.

The involvement of 5-hydroxytryptamine (5-HT) and 5-HT3 receptors and prostaglandin E2 (PGE2) in Salmonella Typhimurium-induced fluid accumulation in the porcine small intestine was investigated. Salmonella Typhimurium (10(8) and 10(10) cfu) and cholera toxin (CT; 20 microg) were instilled for 8 and 11 h in ligated loops in the porcine jejunum and ileum. Fluid accumulation and concentrations of Na+, K+, Cl-, 5-HT and PGE2 in the fluid accumulated in the loops were measured. The fluid accumulation was also measured when Salmonella Typhimurium (10(10) cfu) and CT (20 microg) were instilled for 8 h in ligated loops in jejunum and ileum in pigs given subcutaneous injections of saline or the 5-HT3 receptor antagonist ondansetron (200 microg/kg). Salmonella Typhimurium (10(10) cfu) and CT both induced fluid accumulation in jejunum and ileum after 8 and 11 h. Both treatments also induced an increase in luminal release of 5-HT and PGE2. The accumulated fluid was iso-osmotic and hyperosmotic in CT- and Salmonella Typhimurium-treated loops, respectively. Ondansetron reduced the Typhimurium-induced fluid accumulation in both jejunum and ileum by c. 40%, while it failed to reduce the response to CT. These results demonstrate that 5-HT and PGE2 are released and 5-HT3 receptors activated in the secretory pathway of Typhimurium in the porcine small intestine.

Promoting patient cooperation with exercise programs: linking research, theory, and practice.

Managing patient-nonadherence with prescribed exercise regimens is not an uncommon task for physical therapists working with individuals with arthritis. Yet little is known about the factors that influence patient adherence with exercise programs or therapist knowledge and use of theoretically based adherence management techniques. Survey research with physical therapists and patients was used to provide a database for further insight into the barriers experienced in implementing exercise programs in clinical practice. In this paper, we suggest that the cooperation with an exercise regimen is mediated by the patient's belief system and requires a therapeutic process of mutual inquiry, problem solving, and negotiation between the therapist and patient. Concepts from research, theory, and practice are integrated into a Process Model for Patient-Practitioner Collaboration for use in clinical practice.

Cunninghamella bertholletiae infection in a bone marrow transplant patient: amphotericin lung penetration, MIC determinations, and review of the literature.

Infections caused by Cunninghamella bertholletiae, an opportunistic fungal organism, have an extremely high mortality rate. A fatal case of C. bertholletiae fungal pneumonia occurred in a man who had received an allogeneic bone marrow transplant. Aggressive debridement and high-dose liposomal amphotericin B failed to eradicate the infection. Right lung tissue samples obtained during lobectomy were assayed for amphotericin B concentrations by high-performance liquid chromatography, and minimum inhibitory concentration (MIC) determinations of amphotericin B against C. bertholletiae were determined by the macrobroth dilution method. The MIC for the isolate of C. bertholletiae was 4 microg/ml. Amphotericin B lung concentrations averaged 9.5 microg/ml (range 3.7-13.8 microg/ml), with a corresponding serum trough concentration of 0.9 microg/ml. To our knowledge, this is the first reported case of amphotericin B concentrations measured at the site of infection in a patient with a pulmonary Cunninghamella infection, together with a corresponding MIC of the organism. The patient's death, which occurred despite aggressive debridement and high amphotericin B lung concentrations, highlights the need for novel strategies to treat infections caused by invasive molds such as C. bertholletiae.

The effect of varied hip angles on the generation of internal tibial rotary torque.

Previous researchers have determined that 90 degrees of knee flexion is an appropriate angle to condition the internal tibial rotators. Because the majority of internal tibial rotators are two-joint muscles crossing both the knee and the hip, the influence of the hip angle on the generation of rotary torque was examined. The purpose of this study was to investigate the effect of four hip angles on the generation of internal tibial rotational torque with the knee positioned at 90 degrees of flexion. Forty subjects, 20 males and 20 females, were tested at four positions of hip flexion (120 degrees, 90 degrees, 45 degrees, 10 degrees) using a modified Cybex II isokinetic dynamometer, and their maximal mean internal rotary torque values were recorded. The subjects were placed in a custom-made orthotic-type boot to minimize the motions of the talo-calcaneal joint. Sixty percent of the males and 65% of the females generated their greatest absolute torque value at 120 degrees of hip flexion. A procedure investigating the rankings of the maximal mean torque values at each of the tested hip positions revealed a significant difference between the hip positions of 120 and 10 degrees for both populations (P less than 0.001), and the male population also demonstrated significance between the angles of 120 and 45 degrees and 90 and 10 degrees (P less than 0.05). The practical significance of this study offers some additional information regarding the appropriate positioning for rehabilitation of the internal tibial rotators. The data suggests that if maximal torque generation is desired, the internal tibial rotators should be tested and exercised with the hip flexed to 120 degrees to take advantage of the length-tension relationship and the biomechanical principles of the rotary muscles.

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.

Biomechanics of the lumbar intervertebral disk: a review.

This article reviews the literature on the biomechanics of the lumbar intervertebral disk according to: 1) disk structure and properties, 2) biomechanical principles and their application to the disk, 3) biomechanics and intradiskal pressures as they relate to posture, work, and exercise, and 4) prophylactic measures.

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.

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.

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.

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.

Expert practice in physical therapy.

BACKGROUND AND PURPOSE: The purpose of this qualitative study was to identify the dimensions of clinical expertise in physical therapy practice across 4 clinical specialty areas: geriatrics, neurology, orthopedics, and pediatrics. SUBJECTS: Subjects were 12 peer-designated expert physical therapists nominated by the leaders of the American Physical Therapy Association sections for geriatrics, neurology, orthopedics, and pediatrics. METHODS: Guided by a grounded theory approach, a multiple case study research design was used with each of the 4 investigators studying 3 therapists working in one clinical area. Data were obtained through nonparticipant observation, interviews, review of documents, and analysis of structured tasks. Videotapes made during selected therapist-patient treatment sessions were used as a stimulus for the expert therapist interviews. Data were transcribed, coded, and analyzed through the development of 12 case reports and 4 composite case studies, one for each specialty area. RESULTS: A theoretical model of expert practice in physical therapy was developed that included 4 dimensions: (1) a dynamic, multidimensional knowledge base that is patient-centered and evolves through therapist reflection, (2) a clinical reasoning process that is embedded in a collaborative, problem-solving venture with the patient, (3) a central focus on movement assessment linked to patient function, and (4) consistent virtues seen in caring and commitment to patients. CONCLUSION AND DISCUSSION: These findings build on previous research in physical therapy on expertise. The dimensions of expert practice in physical therapy have implications for physical therapy practice, education, and continued research.

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.

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.

The clinical doctorate: a framework for analysis in physical therapist education.

This article explores major considerations for analysis and discussion of the role of the clinical doctorate as the first professional degree in physical therapist education (DPT). A process for this analysis is posed based on a conceptual framework developed by Stark, Lowther, Hagerty, and Orczyk through grounded theory research on professional education. External influences from society and the profession, institutional and programmatic influences, and articulation of critical dimensions of professional competence and professional attitudes as major categories are discussed in relation to the DPT. A series of questions generated from the application of the model are put forth for continued discussion and deliberation concerning the DPT. We conclude that the DPT provides the best pathway to serve society, the patient, and the profession.