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Biomedical subjects

T Gardner

Publications and source records attributed to T Gardner.

At least 19 recordsLinked to original sources
PubMed2005

Load transmission through a healing tibial fracture.

BACKGROUND: Fracture healing has been linked to both the magnitude and distribution of mechanical stresses on the healing fracture tissues. However, direct clinical measurement of in vivo tibial axial loading is not possible. METHODS: Using computed tomography images, force plate data and recorded 3D interfragmentary micromovements, accurate 3D finite element models of a healing human tibial fracture were generated at 7, 10, and 16 weeks post-fracture and used to calculate longitudinal tibial forces and external fixator load-sharing during bilateral stance and walking. FINDINGS: Tibial load-sharing by the fixator decreased significantly as the fracture tissues developed even moderate stiffness, while tibial load increased steadily towards normal. INTERPRETATION: Quantitative assessment of the contribution of the external fixator is important as overloading of the callus due to insufficient support has been implicated in the retardation of the healing process.

Adult↗
PubMed2005

A comprehensive approach for evaluating telemedicine-delivered multidisciplinary breast cancer meetings in southern Scotland.

Multidisciplinary team (MDT) meetings for decisions on cancer management are a cornerstone of UK cancer policy. We have proposed a comprehensive methodology to assess the clinical and economic effectiveness of telemedicine in this setting, which is being tested in a randomized breast cancer trial. Pre- and post-telemedicine assessment includes attitudes to and expectations of telemedicine, based on semistructured interviews. The communication content of videotapes of the MDT meeting is being scored using Borgatta's revised Interaction Process Analysis System. The technical performance of the telemedicine equipment is reported on a standardized pro forma. A short questionnaire captures key elements of professional satisfaction for each patient discussion (consensus on future management, confidence in and sharing of decision), added value of linkage, group atmosphere, overall conduct of the meeting and compliance with SIGN guidelines. A cost-minimization analysis will be used for economic assessment.

Attitude of Health Personnel↗
PubMed2005

Attitudes of breast cancer professionals to conventional and telemedicine-delivered multidisciplinary breast meetings.

We surveyed the attitudes of breast cancer professionals to standard face-to-face and future telemedicine-delivered breast multidisciplinary team (MDT) meetings. Interviews, which included the Group Behaviour Inventory, were conducted face-to-face (n = 19) or by telephone (n = 26). The mean total score on the Group Behaviour Inventory was 96 (SD 19) for 33 respondents, which indicated satisfaction with standard MDT meetings, irrespective of role and base hospital. Positive attitudes to videoconferencing were more common among participants with previous experience of telemedicine (Spearman's rank correlation 0.26, P = 0.91). Common themes emerging from the interviews about telemedicine-delivered MDTs included group leadership, meeting efficiency, group interaction, group atmosphere and technical quality of communication. Most participants were satisfied with standard breast MDTs. Nurses and allied health professionals were least supportive of telemedicine.

Analysis of Variance↗
PubMed2001

Simple motor gestures for birdsongs.

We present a model of sound production in a songbird's vocal organ and find that much of the complexity of the song of the canary (Serinus canaria) can be produced from simple time variations in forcing functions. The starts, stops, and pauses between syllables, as well as variation in pitch and timbre are inherent in the mechanics and can often be expressed through smooth and simple variations in the frequency and relative phase of two driving parameters

Animals↗
PubMed2001

Continuous model for vocal fold oscillations to study the effect of feedback.

In this work we study the effects of delayed feedback on vocal fold dynamics. To perform this study, we work with a vocal fold model that is made as simple as possible while retaining the spectral content characteristic of human vocal production. Our results indicate that, even with the simplest explanation for vocal fold oscillation, delayed feedback due to reflected sound in the vocal tract can lead to extremely rich dynamics.

Journal Article↗
PubMed2001

Accuracy of predicting long-term prostate specific antigen outcome based on early prostate specific antigen recurrence results after radical prostatectomy.

PURPOSE: We determined how prostate specific antigen (PSA) doubling time changed with time and whether an early measure of doubling time would accurately predict long-term PSA values and clinical outcome in a cohort of patients followed expectantly after radical prostatectomy. MATERIALS AND METHODS: We analyzed data on 121 patients with PSA recurrence after radical retropubic prostatectomy. Group and individual analyses were performed on 60 patients who met study inclusion criteria. PSA doubling time was calculated and a curve was plotted using logarithmic transformation with linear regression and least squares analysis. In analysis 1 patients were placed into 3 subgroups according to doubling time. Doubling time was calculated per subgroup and the slopes of the aggregate curves were compared to determine how doubling time changed with time. In analysis 2 we calculated early doubling time per patient using only the initial 2 detectable PSA values and compared it with eventual doubling time in each using all PSA values. In addition, we analyzed how doubling time correlated with the clinical course. RESULTS: Using the group methodology there was no statistically significant acceleration or deceleration with time in doubling time slope in any of the 3 subgroups. On individual analysis we noted a weak correlation of early with eventual doubling time (correlation coefficient 0.69, p = 0.01). In 88% of patients eventual doubling time was not within 10% of early doubling time. Metastasis developed in 60% of patients with an eventual DT of 0 to 6 months, while 80% with an eventual doubling time of 6 to 12 months had no evidence of local or metastatic disease. No patients with an eventual doubling time of greater than 12 months have had metastatic disease and only 4 (16%) had local recurrence, which was treated with radiation therapy. In 8 of the 14 patients (23%) with local recurrence or metastatic disease early doubling time predicted eventual doubling time. Early doubling time was more rapid and slower than eventual doubling time in 5 and 1, respectively, of the remaining cases, which would have placed them in a different subgroup. CONCLUSIONS: On group analysis PSA doubling time appeared to be constant with time and there was no evidence that it accelerated with time in our dataset of PSA recurrence after radical prostatectomy. On individual analysis early doubling time showed a weak but statistically significant correlation with eventual doubling time. However, there was significant inaccuracy when predicting PSA doubling time based on early PSA values in individuals. Generally early projections of doubling time tend to over predict tumor biological aggressiveness, that is local recurrence or metastasis. A need remains for more accurate predictors of the rate of disease progression at initial PSA recurrence to determine accurately early in the clinical course the patients who may benefit from additional therapy. Currently no patient in our study has died of prostate cancer.

Adult↗
PubMed1998

Mechanical influences on tibial fracture healing.

Selected studies are summarized that measure interfragmentary fracture displacements in 6 degrees of freedom at intervals throughout healing in groups of patients with tibial diaphyseal fractures treated by external skeletal fixation. The results are compared with those obtained from experimental studies in which the ideal mechanical conditions for fracture healing were predicted. A finite element analysis model of the healing tibial fracture also was developed. Measured data were used for the analysis, and stress and strain patterns were defined for different stages of healing. Interfragmentary movement measured in the first 6 weeks after injury usually is a magnitude smaller in patients treated by external fixation than in patients treated with cast immobilization. This movement can be much smaller than that predicted to be optimal by experimental studies. A greater amplitude can be achieved, even in stable fractures, by ensuring patient activity. The interfragmentary movement is elastic during loading activity and is generally sinusoidal during steady walking. At the time of dynamization (the unlocking of the frame), a permanent set occurs at the fracture site in all planes. The cyclical movement range in each plane often decreases immediately after unlocking. The model analysis study of fracture healing predicts that tissue damage may occur in the later (hard callus) phase of healing, even while the fixation device is in place, because of abnormally high stresses and strains. This study indicates that fracture mechanics should be controlled more rigorously to provide amplitudes of movement in the first 4 to 6 weeks after fracture. The rigidity of fixation should be increased in the subsequent weeks until the fracture has healed and the frame is removed.

Bony Callus↗
PubMed1996

Manual assessment of fracture stiffness.

A fracture stiffness of 15 Nm/degree measured biomechanically has been proposed as a reliable indicator of early fracture union. This study used a fracture model to examine the ability of orthopaedic surgeons to assess the stiffness of a fracture manually. Twenty orthopaedic surgeons were tested along with 20 controls. They each estimated the stiffness of seven rods representing mid-shaft diaphyseal fractures at different stages of healing, and were asked whether the stiffness suggested that union had progressed to the stage where the stabilizing device could be removed. Surgeons were unable to estimate the fracture stiffness accurately, and greatly overestimated rod stiffness particularly for the lower values. This meant that on 83 per cent of occasions when the stiffness was less than 15 Nm/degree, the surgeons considered the fracture models united to a sufficient degree to prescribe removal of the fixator. The results suggest that clinical assessment of fracture stiffness alone may put 83 per cent of patients at risk of refracture or malunion. Manual testing of the mechanical stability of a fracture appears not to be reliable.

Biomechanical Phenomena↗
PubMed1996

The role of postoperative irradiation in the management of sphenoid wing meningiomas. A preliminary report.

PURPOSE: To determine whether postoperative radiation therapy decreases recurrence rates in subtotally excised and recurrent sphenoid wing meningiomas. METHODS: Patients with primary subtotally excised and recurrent sphenoid wing meningiomas who underwent surgery between 1981 and 1994 (n = 105) were prospectively followed for recurrence. Postoperative radiation was not recommended in patients who had complete excision; therefore, their recurrence rates were not evaluated in this study. Patients with malignant meningiomas also were excluded from analysis. Recurrence was defined as evidence of tumor growth on neuroimaging with or without clinical symptoms. RESULTS: Follow-up information was available for 86 patients; 69 had primary subtotally excised tumors and 17 had recurrent tumors. Follow-up information was unavailable in the remaining 19 patients. Tumor location and histopathology, type of surgery performed, and patient sex and age were similar in the irradiated and nonirradiated subgroups. Postoperative irradiation was delivered to 31 patients with primary tumors and 11 with recurrent tumors; none of these 42 patients had recurrence during a mean observation period of 4.2 and 3.5 years, respectively. The nonirradiated group consisted of 38 patients with primary tumors and 6 with recurrent tumors; 16 of 18 patients who had primary meningiomas had a recurrence and 5 of 6 who had recurrent tumors had another relapse (mean interval between resection and recurrence, 4.4 years and 14 months, respectively). CONCLUSIONS: Postoperative radiation appeared to delay recurrence in subtotally excised and recurrent sphenoid wing meningiomas during the time frame of this study.

Adolescent↗
PubMed1995

Conversion from 2.5 mg to 1.25 mg indapamide in patients with mild to moderate hypertension.

BACKGROUND: Indapamide is an effective antihypertensive drug with diuretic and vasodilating activities. The common starting dose has been 2.5 mg to 5 mg. A lower dose formulation (1.25 mg) is now available. The safety and efficacy of switching patients from indapamide 2.5 mg to indapamide 1.25 mg was evaluated in this randomized, double-blind, multicenter clinical trial. METHODS: Three hundred seventy-eight adult patients with mild to moderate essential hypertension were enrolled in a washout period, during which patients received single-blind placebo for 4 weeks. All 378 patients qualified for the study and received open-label treatment with indapamide 2.5 mg for 8 weeks. Of the 378 patients, 265 responded to indapamide 2.5 mg and were randomized to receive double-blind treatment with either indapamide 1.25 mg (n = 132) or 2.5 mg (n = 133) for 8 weeks. Overall, 245 of the 378 patients who were initially enrolled completed the study. The primary efficacy variable was the number of patients in each treatment group who maintained a supine diastolic blood pressure of < or = 90 mm Hg (treatment success) by the end of the double-blind period (week 16). RESULTS: Treatment with indapamide 1.25 mg once daily was as efficacious as the 2.5-mg once-daily dose. No significant difference was observed for the percentage of patients who achieved treatment success between the patients switched from indapamide 2.5 to 1.25 mg (74%) and the control group maintained on indapamide 2.5 mg (70%). The incidence of drug-related adverse events during the double-blind period was similar between the two treatment groups. The mean change from pretreatment baseline to endpoint in serum potassium was -0.2 mEq/L (-0.2 mmol/L) in the indapamide 1.25 mg treatment group, compared with -0.4 mEq/L (-0.4 mmol/L) in the indapamide 2.5 mg treatment group. CONCLUSIONS: Indapamide 1.25 mg given once daily for 8 weeks was as effective as 2.5 mg once daily in reducing systolic and diastolic blood pressure in patients with mild to moderate hypertension.

Adult↗
PubMed1994

Myocardial heat shock gene expression in pigs is dependent on superoxide anion generated at reperfusion.

The heat shock response is a conserved response to cell injury. We sought to determine if ischemia alone versus events at reperfusion stimulated expression of the major heat shock protein (hsp-72) in a clinically relevant model of global myocardial ischemia in pigs. Pigs were placed on nonpulsatile cardiopulmonary bypass. Serial transmural cardiac biopsies were taken at baseline following 20 min of normothermic global ischemia (induced by crossclamping the aorta) and at 20, 40, and 60 min of reperfusion. Test animals received a bolus and subsequent aortic root infusion of superoxide dismutase (total 7,500 U/kg) beginning just prior to reperfusion. Hsp-72 mRNA abundance was estimated from Northern blots. We found that hsp-72 mRNA was not induced following 20 min of ischemia but accumulated to high levels within 20 min of reperfusion. Intravascular administration of superoxide dismutase at reperfusion eliminated hsp-72 mRNA induction. We conclude that in the postischemic myocardium, hsp-72 gene expression is dependent on superoxide anion generation at reperfusion. In this setting, hsp-72 gene expression may reflect a specific response to oxidative injury rather than a more general response to metabolic stress associated with ischemia.

Adenosine Triphosphate↗
PubMed1988

Requests for proposals for library automation.

Many health sciences libraries are now considering integrated automated systems for an investment of several hundred thousand dollars. The request for proposals (RFPs) is the usual method of selecting candidate vendors for close inspection of promising systems. This paper draws upon the experience of the Library of Rush University and that of twelve other health sciences libraries. The libraries were interviewed by telephone using a short questionnaire that asked them to compare the RFPs with the systems actually obtained and their experiences in implementing them. The libraries were also asked, with the benefit of hindsight, what would they have done differently. Four vendors were also interviewed by telephone, in order to get their point of view.

Chicago↗
PubMed1986

Fluid-gas exchange and photocoagulation after vitrectomy. Indications, technique, and results.

We describe the indications, complications, and results of postvitrectomy fluid-gas exchange and laser photocoagulation for management of complicated vitreoretinal disease. Indications include proliferative vitreoretinopathy, vitreous opacities associated with proliferative diabetic retinopathy, giant retinal tear, recurrent rhegmatogenous retinal detachment, and trauma. Eyes treated with 50% sulfur hexafluoride gas rather than sterile air demonstrated a higher intraocular pressure on the first postexchange day, which was not a significant source of disease. There was no statistically significant difference in retinal reattachment between eyes treated with gas and those treated with air. Fluid-gas exchange in eyes with partial or total retinal detachment resulted in total or partial retinal reattachment, with the macula attached in 82% of cases within the first 48 hours following exchange. Final reattachment rate, with a mean follow-up of 8.9 months (range, six to 36 months), was 55%. In eyes with proliferative vitreoretinopathy, the combination of postoperative argon or krypton laser photocoagulation with fluid-gas exchange was associated with a final reattachment rate of 75%. Postoperative fluid-gas exchange and photocoagulation appear to be safe and effective advances in the treatment of complicated vitreoretinal diseases requiring vitrectomy.

Body Fluids↗
PubMed1986

Fluorescence identifies an alkaline cell in turtle urinary bladder.

Intracellular pH (pHi) of turtle bladder mucosal cells was studied by the trapped fluorescent indicator technique. Bladders efficiently accumulated and converted 4-methylumbelliferyl acetate to its pH-sensitive derivative 4-methylumbelliferone (4MU). Excited at the pH-indifferent wavelength 334 nm, bladders fluoresced a uniform blue. Using pH-sensitive 365-nm excitation, 10-20% of the mucosal cells fluoresced distinctly brighter, suggesting a more alkaline pHi. Using the 365/334 ratio to quantitate pHi, this difference averaged 0.1 pH units. Bright cells were more distinct after SITS or acetazolamide but disappeared after digitonin permeabilization, dinitrophenol, or treatment with propionate, DMO, and NH4Cl. Essentially the same population of bright cells was identified by carboxyfluorescein diacetate. The brighter cell corresponded exactly to a population of cells with distinctive acridine orange staining and bright costaining with the potential-sensing probes Di-O-C5, Di-S-C3, and 4-Di-5-Asp. Two extremes of bright cell shape were seen: an elongate cell, prevalent under conditions stimulating H+ secretion, and a more compact cell, when acidification was inhibited. These observations support the hypothesis that acidification represents H+ secretion via the luminal membrane and that a primary role of carbonic anhydrase in this process is to support the exit of base from the cell. The more alkaline cells appear to be the carbonic anhydrase-rich cells. These cells are chemically isolated from the surrounding granular cells and change their morphology in response to changes in acidification. These special properties indicate a unique role for the carbonic anhydrase cell in H+ secretion.

Acridine Orange↗
PubMed1985

Role of the crystalline lens in the spatial vision loss of the elderly.

This study examined the contribution of the crystalline lens to the spatial contrast sensitivity loss experienced by many healthy older adults. Spatial contrast sensitivity was measured in three groups of adults: older adults who had undergone cataract extraction and intraocular lens (IOL) insertion; older adults who were in good ocular health (agematched to the first group); and young adults also in good ocular health. Older adults had decreased contrast sensitivity at higher spatial frequencies compared to young adults, agreeing with earlier reports. In addition, both groups of older adults had similar contrast sensitivity at higher frequencies, contrary to what would be expected if the aged, noncataractous crystalline lens significantly hampered contrast transfer in the healthy older eye. Results imply that the crystalline lens is not primarily responsible for the spatial sensitivity loss of healthy older adults. Furthermore, these data indicate that for at least some IOL patients, spatial vision can be restored to a level similar to their agemates who have no history of lens opacity or ocular disease.

Adult↗