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Biomedical subjects

T A Schmidt

Publications and source records attributed to T A Schmidt.

At least 19 recordsLinked to original sources
PubMed2006

Effect of synovial fluid on boundary lubrication of articular cartilage.

OBJECTIVES: The lubrication of articulating cartilage surfaces in joints occurs through several distinct modes. In the boundary mode of lubrication, load is supported by surface-to-surface contact, a feature that makes this mode particularly important for maintenance of the normally pristine articular surface. A boundary mode of lubrication is indicated by a kinetic friction coefficient being invariant with factors that influence formation of a fluid film, including sliding velocity and axial load. The objectives of this study were to (1) implement and extend an in vitro articular cartilage-on-cartilage lubrication test to elucidate the dependence of the friction properties on sliding velocity, axial load, and time, and establish conditions where a boundary mode of lubrication is dominant, and (2) determine the effects of synovial fluid (SF) on boundary lubrication using this test. METHODS: Fresh bovine osteochondral samples were analyzed in an annulus-on-disk rotational configuration, maintaining apposed articular surfaces in contact, to determine static (mu(static) and mu(static),(N(eq)) and kinetic ([mu(kinetic)] and [mu(kinetic),(N(eq))]) friction coefficients, each normalized to the instantaneous and equilibrium (N(eq)) normal loads, respectively. RESULTS: With increasing pre-sliding durations, mu(static) and mu(static),(N(eq)) were similar, and increased up to 0.43 +/- 0.03 in phosphate buffered saline (PBS) and 0.19 +/- 0.01 in SF, whereas [mu(kinetic)] and [mu(kinetic),(N(eq))] were steady. Over a range of sliding velocities of 0.1-1 mm/s and compression levels of 18% and 24%, [mu(kinetic)] was 0.072 +/- 0.010 in PBS and 0.014 +/- 0.003 in SF, and [mu(kinetic),(N(eq))] was 0.093 +/- 0.005 in PBS and 0.018 +/- 0.002 in SF. CONCLUSIONS: A boundary mode of lubrication was achieved in a cartilage-on-cartilage test configuration. SF functioned as an effective friction-lowering boundary lubricant for native articular cartilage surfaces.

Animals↗
PubMed2003

Sexual growth dimorphism affects birth sex ratio in house mice.

We present the first empirical evidence that mammalian sex-ratio deviations result from variation in adult-weight sexual dimorphism via correlated effects on blastocyst development. Two selection lines of mice exhibiting high and low sexual dimorphism in adult weight showed correlated sexual weight differences at birth and at weaning, caused by relatively decelerated growth of males in the low line from before birth. The sex ratio at birth was significantly female-biased in the low line, and significantly lower than in the highly dimorphic line. Concomitantly, blastomere numbers were at significantly higher variance in the low than in the highly dimorphic line, owing to an increased frequency of slowly growing blastocysts. Since low-dimorphism mice produced more corpora lutea and more female pups than the high-dimorphism mice, but not more males, birth sex-ratio bias most parsimoniously resulted from the loss of slowly growing male blastocysts. This is in agreement with the observation that sex-ratio skews in mammals arise when timing of uterine responsiveness (i.e. its temporally limited capacity for implantation) varies in relation to sex-specific embryonic growth rates. Hence, natural mammalian sex-ratio variation that stems from developmental asynchrony might be a by-product of natural selection for sexual dimorphism in adult weight.

Animals↗
PubMed2003

Tissue engineering of stratified articular cartilage from chondrocyte subpopulations.

OBJECTIVE: To test if subpopulations of chondrocytes from different cartilage zones could be used to engineer cartilage constructs with features of normal stratification. ESIGN: Chondrocytes from the superficial and middle zones of immature bovine cartilage were cultured in alginate, released, and seeded either separately or sequentially to form cartilage constructs. Constructs were cultured for 1 or 2 weeks and were assessed for growth, compressive properties, and deposition, and localization of matrix molecules and superficial zone protein (SZP). RESULTS: The cartilaginous constructs formed from superficial zone chondrocytes exhibited less matrix growth and lower compressive properties than constructs from middle zone chondrocytes, with the stratified superficial-middle constructs exhibiting intermediate properties. Expression of SZP was highest at the construct surfaces, with the localization of SZP in superficial-middle constructs being concentrated at the superficial surface. CONCLUSIONS: Manipulation of subpopulations of chondrocytes can be useful in engineering cartilage tissue with a biomimetic approach, and in fabricating constructs that exhibit stratified features of normal articular cartilage.

Animals↗
PubMed2001

Oregon physicians' attitudes about and experiences with end-of-life care since passage of the Oregon Death with Dignity Act.

CONTEXT: The Oregon Death with Dignity Act, passed by ballot measure in 1994 and enacted in October 1997, legalized physician-assisted suicide for competent, terminally ill Oregonians, but little is known about the effects of the act on clinical practice or physician perspective. OBJECTIVE: To examine Oregon physicians' attitudes toward and practices regarding care of dying patients since the passage of the Death with Dignity Act. DESIGN, SETTING, AND PARTICIPANTS: A self-administered questionnaire was mailed in February 1999 to Oregon physicians eligible to prescribe under the act. Of 3981 eligible physicians, 2641 (66%) returned the questionnaire by August 1999. MAIN OUTCOME MEASURES: Physicians' reports of their efforts to improve care for dying patients since 1994, their attitudes, concerns, and sources of information about participating in the Death with Dignity Act, and their conversations with patients regarding assisted suicide. RESULTS: A total of 791 respondents (30%) reported that they had increased referrals to hospice. Of the 2094 respondents who cared for terminally ill patients, 76% reported that they made efforts to improve their knowledge of the use of pain medications in the terminally ill. Nine hundred forty-nine responding physicians (36%) had been asked by a patient if they were potentially willing to prescribe a lethal medication. Seven percent of all survey participants reported that 1 or more patients became upset after learning the physician's position on assisted suicide, and 2% reported that 1 or more patients left their care after learning the physician's position on assisted suicide. Of the 73 physicians who were willing to write a lethal prescription and who had received a request from a patient, 20 (27%) were not confident they could determine when a patient had less than 6 months to live. CONCLUSION: Most Oregon physicians who care for terminally ill patients report that since 1994 they have made efforts to improve their ability to care for these patients and many have had conversations with patients about assisted suicide.

Adult↗
PubMed2000

Physicians' experiences with the Oregon Death with Dignity Act.

BACKGROUND: Physician-assisted suicide was legalized in Oregon in October 1997. There are data on patients who have received prescriptions for lethal medications and died after taking the medications. There is little information, however, on physicians' experiences with requests for assistance with suicide. METHODS: Between February and August 1999, we mailed a questionnaire to physicians who were eligible to prescribe lethal medications under the Oregon Death with Dignity Act. RESULTS: Of 4053 eligible physicians, 2649 (65 percent) returned the survey. Of the respondents, 144 (5 percent) had received a total of 221 requests for prescriptions for lethal medications since October 1997. We received information on the outcome in 165 patients (complete information for 143 patients and partial for on an additional 22). The mean age of the patients was 68 years; 76 percent had an estimated life expectancy of less than six months. Thirty-five percent requested a prescription from another physician. Twenty-nine patients (18 percent) received prescriptions, and 17 (10 percent) died from administering the prescribed medication. Twenty percent of the patients had symptoms of depression; none of these patients received a prescription for a lethal medication. In the case of 68 patients, including 11 who received prescriptions and 8 who died by taking the prescribed medication, the physician implemented at least one substantive palliative intervention, such as control of pain or other symptoms, referral to a hospice program, a consultation, or a trial of antidepressant medication. Forty-six percent of the patients for whom substantive interventions were made changed their minds about assisted suicide, as compared with 15 percent of those for whom no substantive interventions were made (P<0.001). CONCLUSIONS: Our data indicate that in Oregon, physicians grant about 1 in 6 requests for a prescription for a lethal medication and that 1 in 10 requests actually result in suicide. Substantive palliative interventions lead some--but not all--patients to change their minds about assisted suicide.

Attitude of Health Personnel↗
PubMed2000

A randomized controlled trial to assess decay in acquired knowledge among paramedics completing a pediatric resuscitation course.

BACKGROUND: Critical pediatric illness or injury occurs infrequently in out-of-hospital settings, making it difficult for paramedics to maintain physical assessment, treatment, and procedure skills. OBJECTIVES: To document the ability of paramedics to retain clinical knowledge over a one-year interval after completing a pediatric resuscitation course and to determine whether clinical experience or retesting improves retention. METHODS: This was a randomized controlled study assessing retention of knowledge in pediatric resuscitation soon after, six months after, and 12 months following completion of a pediatric advanced life support course. Forty-three paramedics participated in pre- and post-pediatric resuscitation course testing and were randomly assigned to one of four groups. Group 1 received a knowledge examination (KE) and mock resuscitation scenarios (MR) at six months. Group 2 received only the KE at six months. Group 3 received the MR only at six months. Group 4 received no intermediate testing. All groups were reassessed at 12 months. RESULTS: Pediatric clinical knowledge (as measured by KE) rose sharply immediately after the course but returned to baseline levels within six months. There was no difference between the groups in knowledge scores at 12 months, despite the interventions at six months. CONCLUSIONS: Although intensive out-of-hospital pediatric education enhances knowledge, that knowledge rapidly decays. Emergency medical services programs need to find novel ways to increase retention and ensure paramedic readiness.

Adolescent↗
PubMed2000

Receptor occupancy with digoxin vs receptor occupancy with a putative endogenous digitalislike factor.

The possibility that an endogenous ligand for the digitalis receptor might exist has been a source of speculation resulting in efforts over the past decades to identify such a hormone. In the current context it is of interest that prolonged wash of myocardial and skeletal muscular samples from subjects who were not in digoxin treatment generally resulted in small tendencies to increase 3H-ouabain binding ranging from 2 to 9% and from -2 to 7%, respectively. It may be appreciated that neither wet weight nor water content of left ventricular or skeletal muscular samples have been found to change as a result of the prolonged wash. Although these tendencies most likely are a mere play of chance, it may be argued that the studies did not entirely rule out the possibility of the existence of a quantitatively small amount of endogenous digitalislike factor. However, based on the evaluations of receptor occupancy with digoxin during treatment of 24-34% in the left ventricle and 9-13% in skeletal muscle, it would seem reasonable to expect that a comparatively larger fraction of digitalis receptors should be occupied by a putative endogenous digitalislike factor, if such a factor were to be of any physiological significance.

Binding, Competitive↗
PubMed2000

Flexibility of lumbar spinal motion segments correlated to type of tears in the annulus fibrosus.

OBJECT: The authors conducted a study in which their objective was to measure the effect of tears in the annulus fibrosus on the motions of lumbar spinal motion segments. METHODS: Lumbar spinal motion segments were harvested from human cadavers and studied using a 1.5-tesla magnetic resonance imager. The motion segments were subjected to incremental flexion, extension, rotation, and lateral bending torques. Displacements and rotations were measured using a kinematic system. The segments were sectioned on a cryomicrotome to verify the presence of tears in the annulus fibrosus. CONCLUSIONS: Tears in the annulus fibrosus increase the amount of motion that results from a torque applied to the motion segment. Radial and transverse tears of the annulus fibrosus have a greater effect on motions produced by an axial rotatory torque than on those produced by flexion, extension, or lateral bending torques. The difference between normal discs and discs with annular tears is more marked during moments of axial rotational than during those of flexion, extension, or lateral bending.

Aged↗
PubMed1999

Suicidal patients in the ED: ethical issues.

Emergency physicians frequently are expected to evaluate and develop treatment plans for potentially suicidal patients. The struggle to prevent someone from self-injury while respecting their personal autonomy is frequently present in the ED, as physicians must decide whether to intervene with a patient who does not seek treatment. The implications of this struggle are discussed in the article.

Emergency Medicine↗
PubMed1998

The stiffness of lumbar spinal motion segments with a high-intensity zone in the anulus fibrosus.

STUDY DESIGN: Biomechanical and anatomic study of human cadaveric spinal motion segments. OBJECTIVES: To measure the stiffness of spinal motion segments by disc type and by load type (flexion, extension, axial rotation, or lateral bending). To compare stiffness in motion segments with and without a high-intensity zone or radial tear in the anulus fibrosus. SUMMARY OF BACKGROUND DATA: The high-intensity zone, that is a linear zone of high-intensity on T2-weighted magnetic resonance images corresponding to a radial tear in the anulus fibrosus, is a marker for a painful disc at discography. The high-intensity zone is hypothetically associated with diminished stiffness of the motion segment. METHODS: Human cadaveric lumbar spinal motion segments with normal disc morphology or a high-intensity zone of the anulus fibrosus were selected on the basis of magnetic resonance imaging. The motion segments were subjected to incremental flexion, extension, rotation, and lateral bending torques. Rotation was measured with a kinematic system. Torque-rotation curves and stiffness were calculated for each motion segment and for each torque. The motion segments were sectioned on a cryomicrotome to verify the disc morphology as normal or as that of a radial tear. RESULTS: In four motion segments with normal discs, stiffness was greater in axial rotation (8.4 Nm/degree) than in lateral bending (2.3 Nm/degree), flexion (1.8 Nm/degree), or extension (2.6 Nm/degree). In 16 motion segments with a high-intensity zone, stiffness was 2.4 Nm/degree in axial rotation, and less severely reduced in lateral bending, flexion, and extension. Stiffness in motion segments with a high-intensity zone was significantly less with smaller than with larger axial rotation loads. CONCLUSIONS: The presence of a high-intensity zone in the intervertebral disc is associated with reduced stiffness of motion segments. The reduction is greater in axial rotation than in other torques. The reduction is more in smaller than in larger axial torques.

Aged↗
PubMed1998

Do patients refusing transport remember descriptions of risks after initial advanced life support assessment?

OBJECTIVE: To determine patient recall and understanding of instructions given to patients who refuse transport after initial paramedic assessment and medical treatment. METHODS: Following patient consent, a phone interview was completed for consecutive persons living in a large urban area for whom 9-1-1 was contacted but who subsequently refused transport after advanced life support (ALS) assessment. Subjects were asked about their recall of explained risks and benefits of transport, their understanding of those risks at the time of assessment, and subsequent use of medical care, including hospitalization. RESULTS: From October 1, 1996, to February 23, 1997, 324 people refused transport after ALS arrival. Sixty-eight people could not be contacted, providing a response rate of 79% (256/324). Six percent were subsequently admitted to the hospital for the same problem and an additional 59% sought care from a health care provider (66 ED visits, 63 personal physician, 16 urgent care, 5 other). There were no unexpected deaths. Ninety (35%) respondents were still experiencing symptoms at the time of phone contact. Despite the routine practice of providing a verbal explanation of risks and written instructions, only 141 (55%) recalled receiving written instructions and 56 (22%) recalled an explanation of risks. Twenty-six percent believed they did not fully understand their conditions or circumstances surrounding the 9-1-1 call when they refused transport and 18% would now take an ambulance if the same incident were to recur. CONCLUSION: A substantial proportion of patients refusing transport do not recall receiving verbal or written instructions and would reconsider their transport decision, raising doubts about people's ability to make informed decisions at a time of great vulnerability. The majority of patients accessed health care after refusing transport and 6% were hospitalized.

Emergency Medical Services↗
PubMed1998

Oregon emergency medical technicians' attitudes toward physician-assisted suicide.

OBJECTIVES: To determine Oregon intermediate and advanced emergency medical technicians' (EMTs') attitudes toward physician-assisted suicide (PAS) and factors associated with those attitudes. METHODS: An anonymous survey was sent to a random sample of 498 EMTs registered in Oregon. RESULTS: Surveys were delivered to 498 EMTs and 343 completed surveys were returned, for a response rate of 69%. The mean age of the respondents was 37.5 years (+/-8.73) and 79% were male. 232 (68%) agreed that PAS should be legal, 263 (77%) agreed that terminally ill people have a right to decide to commit suicide, while 57 (17%) thought not attempting resuscitation would be immoral. 251 (73%) reported seeing attempted suicide in terminally ill patients at least once, with 117 (34%) experiencing such calls >5 times. Only 22 (6%) stated that they would be unable to work in a system that directed them to withhold resuscitation after a PAS attempt, and 277 (81%) agreed that treatment protocols should direct EMTs to withhold resuscitation. 105 (31%) thought EMTs should participate in the decision to withhold resuscitation. 206 (60%) thought the law should allow lethal injection for terminally ill patients. 201 (59%) agreed there were circumstances under which they might personally consider PAS. If PAS were legal, EMTs stated they would withhold treatment from a terminally ill patient following attempted suicide in the following circumstances: based on standing orders, 78%; with on-line medical direction, 67%; after speaking with the primary physician, 53%; if the patient had decision-making capacity, 45%; with written documentation from the patient's physician, 68%; and never, 6%. CONCLUSIONS: A majority of Oregon EMTs responding to this survey expressed support for PAS, think treatment protocols should direct paramedics to withhold resuscitation in such cases, and would feel comfortable withholding resuscitation given appropriate protocols. Nearly 3 out of 4 Oregon EMTs report seeing at least 1 terminally ill patient who had attempted suicide.

Adult↗
PubMed1997

Multiple options and unique pathways: a new direction for EMS?

The same forces transforming the health care delivery system also are reshaping EMS. The changing economic and organizational structures of the health services delivery system may predict how EMS systems will redesign themselves. We discuss one template for future EMS systems.

Decision Support Techniques↗