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Biomedical subjects

M Litt

Publications and source records attributed to M Litt.

At least 235 records · Page 13Linked to original sources
PubMed1968

Artificial membranes: a new type of cell for measuring diffusional resistance.

A novel technique allows determination of membrane diffusivities and eliminates the complications of the fluid resistance to mass transfer on either side of the membrane. Results on the permeability of a dialysis membrane of the type used in artificial kidneys agree with previous data and are obtained in much shorter time. The measured activation energy for diffusion demonstrates that the transport of salt through the membrane occurs by the same mechanism as the diffusion of salt in water, but that only 10 percent of the membrane surface is effective.

Dialysis↗
PubMedDate not supplied

Clinical and psychological correlates of lumbar motion abnormalities in low back disorders.

BACKGROUND CONTEXT: Low back pain (LBP) and low back disorders (LBDs) identify a complex constellation of conditions that frustrate both diagnosis and therapy. Dynamic quantitative assessment and questionnaire instruments directed toward psychosocial and situational variables provide potentially powerful tools for determining functional pathology and potentially outcome. PURPOSE: Our goal was to independently assess clinical correlates of a trunk motion measurement device, the lumbar motion monitor (LMM). The reliability of the LMM as a clinical test was assessed by comparison with an independent medical examination and biobehavioral questionnaires. STUDY DESIGN/SETTING: There were three study components. A multispecialty physician panel that administered a structured physical examination contributed to a clinical correlation case series study. Standardized outcomes and risk identification questionnaires were administered to the case population. Finally, the LMM was administered in a customary fashion to the same population. PATIENT SAMPLE: Nineteen subjects were recruited on the basis of criteria that included symptoms of chronic recurrent low back pain. This was an employed and active, although impaired, population. Eighteen of the subjects were currently employed with limited lost work time, but chronic and recurrent pain was a common feature. OUTCOME MEASURES: Questionnaire outcome measures were both characterologic and situation based. In addition to providing diagnoses, the physician panel was also asked to offer certain qualitative assessments, such as rehabilitative potential and functional level pertinent to activities of daily living. The impact of LMM measures on physician decision making was also assessed. Trunk angular measurements were used to assess function of patients with chronic low back disorders. METHODS: Kinematic performance on the LMM was expressed as three probability scores. These were the likelihood of abnormality, the "sincerity of effort" (exacerbation or aggravation of impairment), and the likelihood of structural anatomic disease. These variables were examined against established self-report measures of pain and disability. RESULTS: The LMM and physician panels were in agreement on the presence or absence of abnormality. LMM findings tended to be more consistent with clinical history than the clinical examination. The LMM results were also generally consistent with the self-reported measures of pain and disability: a high likelihood of structural disease was associated with depression, somatization, poor health perception and diminished vitality. CONCLUSIONS: The LMM appears to be a useful assessment tool for gauging the presence of LBP and LBD. It was accurate in detecting abnormality when abnormality was determined by clinical history and physician diagnosis. The LMM's differentiation of mechanical low back disease (nonanatomically specific disorders) from structurally specific low back disease was not consistent with a parallel clinical differentiation. Larger trials in a prospective format and studies on a chronically disabled population seem warranted. In an impaired but less disabled population, elevated pain and somatization did not appear to weaken the effort during testing.

Adult↗
PubMedDate not supplied

UK budgetary systems and new health-care technologies.

OBJECTIVES: This article outlines the budgetary setting within the UK health-care system. METHODS: It is argued that while prospective budgets can give rise to efficient resource allocation outcomes, this relies on the budget being set at an appropriate level and the accompanying incentive structures being efficient. The organizational structures and the interrelationships are critical. The recent history of UK National Health Service reforms and expenditure is outlined. It is suggested that until recently, although the budget system has the potential to promote efficiency, the aggregate budget allocated to the NHS has probably been too low given public expectations, technology advances, and preferences for health care. RESULTS: The aggregate budget is due to rise considerably over the next 5 years. While some incentive and regulatory provisions will move the budget toward an efficient allocation many microlevel incentive issues remain. CONCLUSION: Whether efficient patterns of health-care allocation emerge remains open to debate, however, because the existing incentive mechanisms are not optimal.

Biomedical Technology↗
PubMedDate not supplied

Effects of various drugs on canine tracheal mucociliary transport.

A study of the effects of dehydration, atropine, terbutaline and N-acetylcysteine on canine tracheobronchial mucus is presented. Mucociliary clearance rates, mucus secretion volumes and mucus rheologic properties were studied. Clearance rates were studied by a radioisotope technique, mucus collected by a canine "tracheal pouch" method and rheologic studies performed on a microrheometer. Clearance rate was unaffected by dehydration and terbutaline, increased by N-acetylcysteine and decreased by atropine. Secretion volume was increased by terbutaline while dehydration and atropine were without effect. Rheologic factors were increased by dehydration and atropine while terbutaline was without an effect. The effects of N-acetylcysteine on secretion volume and rheologic properties could not be studied because of the nature of the techniques employed.

Acetylcysteine↗
PubMedDate not supplied

Drugs affecting clearance of middle ear secretions: a perspective for the management of otitis media with effusion.

Otitis media with effusion (OME) is characterized by the production and accumulation in the middle ear of mucus secretions, whose physicochemical properties are an important feature in the etiology and treatment of the disease. Many types of pharmaceutical agents, including anti-inflammatory agents, antihistamines, antibiotics, and mucolytics, have been used in attempts to improve the clinical status of patients with OME. This study critically reviews the literature from the point of view of possible changes induced by these agents in the physicochemical properties of the secretions and hence their clearance from the middle ear. In vitro studies on mucociliary clearance of respiratory (tracheobronchial) secretions and middle ear effusions are cited as the basis for analyzing the important parameters expected to govern middle ear clearance and to determine the rationale for use (or nonuse) of various classes of drugs. It is expected that this analysis will prove useful in the design of properly controlled trials of such agents.

Animals↗
PubMedDate not supplied

Rheologic and transport properties of middle ear effusions from cleft palate patients.

Middle ear effusions represent respiratory secretions which are physiologically important to functional mucocilliary transport systems. Knowledge of middle ear mucus and methods of facilitating clearance continue to be important to cleft palate patients. Middle ear mucus was collected from the ears of children with cleft palate before surgical correction. Samples were dialyzed and lyophilized to yield mucus powder. This mucus was reconstituted at various nondialyzable solids (NDS) concentrations in TRIS-CI buffer. A physiochemical study of the middle ear mucus was then undertaken, since a mucociliary transport defect leading to serous otitis media (SOM) is an etiologic possibility.

Child↗
PubMedDate not supplied

Rheology of the vitreous body. Part I: Viscoelasticity of human vitreous.

The rheological properties of the vitreous body of the eye are believed to be a function of composition and to differ among species, as well as to vary regionally within the vitreous. These properties are essential to the mechanical functioning of the eye. Although there are gross, qualitative data on vitreous rheology available in the literature, quantitative rheological measurements on human vitreous and on eyes of other species are sparse and incomplete. The aim of the research reported in this series of papers is to study the rheological behavior of human, bovine, and porcine vitreous, to measure the macromolecular and electrolyte content of these samples, and to correlate and compare these values for the different species as a function of location in the vitreous. In this paper, the rheological model used to correlate viscoelasticity of the vitreous is presented, and a detailed description of the rheological instrumentation and methods of analysis used is given. Data on the rheological properties of human vitreous, as a function of location within the eye, are presented. The results show that in the human eye there are significant differences in a number of the viscoelastic parameters as a function of location within the vitreous body.

Elasticity↗
PubMedDate not supplied

Rheology of the vitreous body: Part 2. Viscoelasticity of bovine and porcine vitreous.

The viscoelastic properties of the vitreous body from bovine and porcine eyes were determined by microrheometry. Each vitreous sample was sectioned into anterior, central and posterior segments. The rheological properties of each species and region were compared with each other and with the viscoelastic properties of human vitreous reported earlier. The results showed significant variations among species, as well as between regions in all species. All regions of human vitreous have significantly different rheological properties from those of the cow, and from the anterior and posterior regions of the pig; however, the viscoelastic behavior of the central porcine region closely resembles that of the human. In comparing the three species, the major differences found are in those parameters characterizing "viscous" or dissipative properties; values of "elastic" or energy storage properties were similar.

Animals↗
PubMedDate not supplied

Rheology of the vitreous body: part 3. Concentration of electrolytes, collagen and hyaluronic acid.

The vitreous body from bovine, porcine, and human eyes was analyzed for concentration of selected components. Each vitreous sample was sectioned into anterior, central, and posterior segments. The segments were analyzed for concentration of Ca+2, Cl-, Na+, and K+, as well as of Collagen and Hyaluronic acid. The four electrolytes showed significant differences between species, but no significant regional variations. The two macromolecules showed significant differences with respect to both species and region within the vitreous. Comparison of these results with previously determined rheological values for the three species revealed a number of unexpected results, such as higher polymer concentrations on average being associated with lower values of viscosity parameters. The results are analyzed in terms of possible compositional differences among species and effects of electrolytes on the viscoelastic behavior of the vitreous' macromolecules.

Animals↗