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Biomedical subjects

J S Ulbrecht

Publications and source records attributed to J S Ulbrecht.

At least 19 recordsLinked to original sources
PubMed2001

Vibration perception threshold testing in patients with diabetic neuropathy: ceiling effects and reliability.

AIMS: To test the reliability of a new vibrometer (Maxivibrometer) which was constructed so that vibration perception threshold (VPT) could be determined without the disadvantage of the off-scale measurements frequently experienced with the Biothesiometer. METHODS: The two devices were compared and tested on a group of diabetic neuropathic subjects and a group of healthy, matched control subjects. VPT was tested on the plantar surface of the feet. RESULTS: The Maxivibrometer gave an actual measurement in all cases even if subjects were severely neuropathic. The replication-to-replication and day-to-day intraclass correlation coefficients for the Maxivibrometer VPT were, except in one case, above 0.94, indicating excellent reliability. The Biothesiometer VPT could also be measured with excellent reliability but only within a limited range of mild to moderate neuropathy, so it appears to be an appropriate screening tool. The replication-to-replication intraclass correlation coefficient was 0.93. CONCLUSIONS: Because VPT could be measured over a wide range with the Maxivibrometer, it was demonstrated that loss of sensation in diabetic neuropathy can progress far beyond the maximum VPT value of the Biothesiometer. The wide measurement range and the excellent reliability make the Maxivibrometer a valuable research tool to quantify loss of sensation, particularly in the presence of severe neuropathy and to record changes over time. Diabet. Med. 18, 469-475 (2001)

Diabetic Neuropathies↗
PubMed2000

Fluid snacks to help persons with type 1 diabetes avoid late onset postexercise hypoglycemia.

PURPOSE: The present study assessed whether whole milk, skim milk, or two commercially available sports drinks are effective in preventing late onset postexercise hypoglycemia (LOPEH) in persons with type 1 diabetes mellitus. METHODS: Subjects ingested water, whole milk, skim milk, sport drink A (carbohydrate and electrolytes), or sport drink B (carbohydrate, fat, and protein) before, during, and after 1 h of bicycle exercise at 60% VO2max in the late afternoon. Drinks were isocaloric (470 +/- 150 kcal) and the number of calories consumed was based on individual energy expenditure. No adjustment in insulinization was allowed in anticipation of exercise. RESULTS: During water trials all subjects became hypoglycemic. Most drinks lead to a moderate hyperglycemia (range of mean values = 200-280 mg x dL(-1)) during the period between the end of exercise and dinner, but this was not the case for whole milk (range 80-120 mg x dL(-1)). Glycemia peaked about 1.5 h after dinner and declined over the next 90 min. Persistent hyperglycemia (range of means = 200-310 mg x dL(-1)) from after exercise to about 4 h postexercise was observed with sports drink B. A decline in glycemia in the evening was greatest during the skim milk trial and required subjects to ingest more carbohydrate as a late evening snack. The least decline during this period occurred during the whole milk trial. Subjects experienced pre-bed and early morning (0300 h) hypoglycemia in 7 of the 28 trials. CONCLUSIONS: These data show that whole milk and sports drinks that are designed for both quick (sport drink A) and long lasting (sport drink B) nutrient replenishment can be used by persons with type 1 diabetes in an effort to avoid LOPEH.

Adult↗
PubMed2000

Muscle damage impairs insulin stimulation of IRS-1, PI 3-kinase, and Akt-kinase in human skeletal muscle.

Physiological stress associated with muscle damage results in systemic insulin resistance. However, the mechanisms responsible for the insulin resistance are not known; therefore, the present study was conducted to elucidate the molecular mechanisms associated with insulin resistance after muscle damage. Muscle biopsies were obtained before (base) and at 1 h during a hyperinsulinemic-euglycemic clamp (40 mU x kg(-1) x min(-1)) in eight young (age 24+/-1 yr) healthy sedentary (maximal O(2) consumption, 49.7+/-2.4 ml x kg(-1) x min(-1)) males before and 24 h after eccentric exercise (ECC)-induced muscle damage. To determine the role of cytokines in ECC-induced insulin resistance, venous blood samples were obtained before (control) and 24 h after ECC to evaluate ex vivo endotoxin-induced mononuclear cell secretion of tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, and IL-1beta. Glucose disposal was 19% lower after ECC (P<0.05). Insulin-stimulated insulin receptor substrate (IRS)-1 tyrosine phosphorylation was 45% lower after ECC (P<0.05). Insulin-stimulated phosphatidylinositol (PI) 3-kinase, Akt (protein kinase B) serine phosphorylation, and Akt activity were reduced 34, 65, and 20%, respectively, after ECC (P < 0.05). TNF-alpha, but not IL-6 or IL-1beta production, increased 2.4-fold 24 h after ECC (P<0.05). TNF-alpha production was positively correlated with reduced insulin action on PI 3-kinase (r = 0.77, P = 0.04). In summary, the physiological stress associated with muscle damage impairs insulin stimulation of IRS-1, PI 3-kinase, and Akt-kinase, presumably leading to decreased insulin-mediated glucose uptake. Although more research is needed on the potential role for TNF-alpha inhibition of insulin action, elevated TNF-alpha production after muscle damage may impair insulin signal transduction.

Adult↗
PubMed2000

Design criteria for rigid rocker shoes.

In this study nine different rigid rocker shoe designs were tested in 17 symptom-free male subjects and compared with the control condition of a flexible, non-rockered extra-depth shoe with the same flat insole. Effects of both rocker height and axis location were explored. Peak pressure was reduced at most forefoot locations by rocker shoes, but increased in the midfoot and heel. Axis location was found to have an important effect, particularly on hallux pressures. On average the best axis location for reducing metatarsal head (MTH) pressure was in the region of 55-60% of shoe length, while for the toes it was 65%. There was a mean trend towards optimal reduction of pressure in one of the rocker shoe conditions at each anatomical location, but the axis position for this optimal placement was variable across subjects and anatomical locations. While most configurations of the rocker shoes were superior to the control shoe, no single configuration was optimal for all subjects at all sites or even for all subjects at the same site. Therefore, some form of plantar pressure measurement in conjunction with gait training to ensure correct use of the rocker shoes would appear to be essential if the pressure reducing effect of the rigid rocker bottom shoe is to be optimized.

Adult↗
PubMed1999

Neuropathic gait shows only trends towards increased variability of sagittal plane kinematics during treadmill locomotion.

Patients with diabetes mellitus (DM) and peripheral neuropathy (PN) are at greater risk of falling and of suffering injuries during falls. It has been hypothesized that PN leads to changes in gait variability that may account for this increased risk. The purpose of this investigation was to analyze the variability of the sagittal plane kinematics of diabetic neuropathic (NP), diabetic non-neuropathic (NNP) and age- and weight-matched control subjects (Control) during motorized treadmill walking at constant speed. While there were distinct trends towards increased variability within the three diagnostic groups (NP > NNP > Control) for several measures of gait variability, most of these trends were not statistically significant. We hypothesize that motorized treadmill walking may be inherently less variable than overground walking and that statistical measures of variability may not be sufficient to fully characterize stride-to-stride variability in human locomotion.

Accidental Falls↗
PubMed1999

Elevated plantar pressure and ulceration in diabetic patients after panmetatarsal head resection: two case reports.

Panmetatarsal head resection (variously called forefoot arthroplasty, forefoot resection arthroplasty, the Hoffman procedure, and the Fowler procedure) was developed for the relief of pain and deformity in rheumatoid arthritis. Although there are successful retrospective series reported in the literature, such an approach is not supported by carefully designed controlled trials. This procedure has also been advocated by some for the relief of plantar pressure in diabetic patients who are at risk for plantar ulceration. The efficacy of the procedure in this context is not supported by existing pressure measurements on rheumatoid arthritis patients in the literature, which has tended to show that although pain relief is obtained, the procedure results in elevation of forefoot pressure. Case reports are described of two patients (three feet) with sensory neuropathy who presented to our clinic 1 to 2 years after panmetatarsal head resections had been performed. Peak plantar pressures in these feet during first step gait were above the 99th percentile and outside the measuring range of the device used (EMED SF platform; NOVEL Electronics Inc., St. Paul, MN). Both patients had also experienced plantar ulcers subsequent to the surgery. Combining the information on patients with rheumatoid arthritis (RA) with that from our two case studies, we conclude that panmetatarsal head resection does not necessarily eliminate focal regions of elevated plantar pressure.

Aged↗
PubMed1998

Sibutramine reduces food intake in non-dieting women with obesity.

Sibutramine (SIB), an inhibitor of serotonin and noradrenaline reuptake, has been shown in clinical trials to be associated with a dose-related decrease in bodyweight. This double-blind, placebo-controlled, Latin square crossover study examined whether the effect on bodyweight could be due in part to a reduction in daily food intake. Twelve non-dieting, women with obesity (body mass index of 30.5 to 41.9) received three treatments (0 [matching placebo], 10, or 30 mg SIB/day) for 14 days, with 14-day washout periods in between. On days 7 and 14, participants came to the laboratory to eat breakfast, lunch, and dinner so that daily energy and macronutrient intakes and ratings of hunger and satiety could be measured. Significant reductions occurred in food intake (both grams and energy) over the 14-day study period. On day 7, SIB 30 reduced intake significantly by 1762 kJ (23% reduction from placebo), and on day 14, both SIB 10 and SIB 30 significantly reduced intake compared with placebo (SIB 10, 19% reduction [1490 kJ]; SIB 30, 26% reduction [2079 kJ]). On day 7, the percentage of energy consumed from carbohydrate increased significantly with the 30-mg dose (56.7%) compared with that of placebo (51.4%), with a reciprocal decrease in energy from fat (27.8% to 24%). The results show that SIB reduced energy intake in women with obesity who were not attempting to lose weight.

Appetite Depressants↗
PubMed1998

The role of muscle spindles in ankle movement perception in human subjects with diabetic neuropathy.

The objective of this study was to develop a quantitative method to assess muscle spindle function. Three groups of subjects were studied: ten young and healthy subjects, 15 older subjects with diabetic neuropathy, and 15 age-matched controls. All subjects performed an ankle-movement matching task with and without muscle vibration. Input from the plantar cutaneous mechanoreceptors was minimized by using a foot-clamping device. The younger subjects tracked the movement very well, but vibration had a significant effect on their performance (P < 0.001). Similar results were seen in the older control subjects, but they were less successful in tracking movement and slightly less affected by vibration. The neuropathic subjects had the most difficulty tracking, and vibration had only a small but still significant effect on their performance. The interaction between the group and the vibration effect was highly significant (P < 0.001), indicating that the performance of the control subjects changed to a greater degree in the presence of vibration than the performance of the subjects with diabetic neuropathy. Muscle spindles are the primary receptors that are involved in the change in tracking performance when vibration is added during an ankle-movement matching task, and we therefore conclude that the procedure described provides a quantitative evaluation of muscle spindle function. The results demonstrate that diabetic neuropathy degrades muscle sensory function, which may contribute to the impaired balance and unsteadiness of gait that has been observed in diabetic neuropathy.

Achilles Tendon↗
PubMed1998

The non-healing diabetic foot wound: fact or fiction?

Wounds on the feet of diabetic patients are often labeled as "non-healing." This article discusses the basis for and the dangers of such a classification. The evidence suggests that if the foot has an adequate vascular supply and no significant infection, a plantar wound that does not heal is the result of poor treatment and/or poor compliance. Wounds that do not heal despite optimal treatment and compliance are extremely rare and need to be referred to the appropriate specialist for care.

Diabetic Foot↗
PubMed1997

The total contact cast: a method for treating neuropathic diabetic ulcers.

Plantar ulcers that do not heal in patients with diabetes and peripheral sensory neuropathy have been shown to be precursors of lower extremity amputation. The total contact cast is considered by many authorities to be the most effective technique for healing of wounds in the neuropathic extremity, yet it still is not widely used in clinical practice. Use of the total contact cast allows mobilization and results in diminished edema and decreased pressure over the ulcerated area. Complete healing usually occurs in eight weeks or less. Total contact casting with careful follow-up should be considered as a useful modality for healing plantar ulcers in diabetic patients with neuropathy of the extremities.

Adult↗
PubMed1997

The effect of insoles in therapeutic footwear--a finite element approach.

Current practice in the prevention of recurrence of neuropathic foot ulcers is to prescribe accommodative in-shoe orthoses or insoles which reduce plantar pressure levels at locations of bony prominences, particularly under the metatarsal heads. To date, design of these orthoses has largely been a trial and error process. There is little quantitative information available regarding the effects of thickness and the influence of soft tissue characteristics on the cushioning effect of such interventions. The current paper investigated alterations in pressure under the second metatarsal head as a function of insole thickness and tissue thickness. Both experimental and quasi-static plane strain finite element approaches were employed. The orthoses chosen reduced plantar pressure by a maximum of approximately 30% and were more effective (on a percentage basis) in the setting of reduced sub-metatarsal tissue thickness. Peak normal stresses predicted by the FE models were, on average, within 5.9% of experimentally measured values for the normal tissue case and 8.1% for the reduced tissue case. The techniques presented represent a promising approach to understanding plantar cushioning and the principles involved in the design of therapeutic footwear for insensate feet.

Equipment Design↗
PubMed1997

The mechanism of plantar unloading in total contact casts: implications for design and clinical use.

Although the total contact cast (TCC) has been shown to be an extremely effective treatment for the healing of plantar ulcers in diabetic patients, little is known about the biomechanics of its action. In this study, plantar pressure and ground reaction force measurements were obtained from over 750 foot contacts as five subjects with known elevated plantar forefoot pressures walked barefoot, in a padded cast shoe, and a TCC. Peak plantar pressures in the forefoot were markedly reduced in the cast compared with both barefoot and shoe walking (reductions of 75% and 86% respectively, P < 0.05). Peak plantar pressures in the heel were not, however, significantly different between the shoe and the TCC, and the longer duration of heel loading resulted in an impulse that was more than twice as great in the cast compared with the shoe (P < 0.05). An analysis of load distribution indicated that the mechanisms by which the TCC achieves forefoot unloading are (1) transfer of approximately 30% of the load from the leg directly to the cast wall, (2) greater proportionate load sharing by the heel, and (3) removal of a load-bearing surface from the metatarsal heads because of the "cavity" created by the soft foam covering the forefoot. These results point out some of the "essential design features" of the TCC (which are different from what had been previously supposed), support the use of the TCC for healing plantar ulcers in the forefoot, but raise questions about its utility in the healing of plantar ulcers on the heel.

Adult↗
PubMed1996

Diabetic sensory neuropathy effect on ankle joint movement perception.

OBJECTIVE: To determine if diabetic subjects with lower extremity cutaneous sensory neuropathy also have a loss of ankle joint movement perception. The strength of association between measurements of ankle joint movement perception and measures of cutaneous sensory function was also investigated. DESIGN: Diabetic subjects with and without sensory neuropathy and individuals without diabetes participated in this study. SETTING: All subjects were community-living individuals. PARTICIPANTS: Fifty-one subjects, ages 40 to 68. Seventeen of the 34 subjects with diabetes had significant distal sensory neuropathy as determined by cutaneous perception of mechanical vibration. All individuals without diabetes were volunteers from the community. Most subjects with diabetes were recruited through direct referral from their physicians. INTERVENTIONS: Ankle joint movement perception threshold (JMPT) was assessed using a device designed for this study. Cutaneous sensory function under both halluces was measured for vibration perception using a vibrometer and for touch-pressure perception using Semmes-Weinstein monofilaments. MAIN OUTCOME MEASURES: Ankle JMPTs (degrees) were compared to measurements of cutaneous vibration perception (volts) and touch-pressure perception (monofilaments force ratings). RESULTS: Diabetic subjects with cutaneous sensory neuropathy demonstrated a significant loss of ankle movement perception (p < .01). Correlation between JMPT and cutaneous sensory tests ranged from Spearman's rank r = .43 to .67. CONCLUSIONS: Although individuals with cutaneous sensory loss secondary to diabetic neuropathy also demonstrated loss of movement perception at the ankle, the relatively low explained variance between the two types of assessment (18% to 45%) indicates that the severity of ankle joint movement perception deficits cannot be directly implied from cutaneous sensory tests.

Adult↗
PubMed1996

Foot function in diabetic patients after partial amputation.

The function of partially amputated feet in 10 patients with diabetes mellitus was studied. First-step bilateral barefoot plantar pressure distribution and three-dimensional kinematic data were collected using a Novel EMED platform and three video cameras. Analysis of the plantar pressure data revealed a significantly greater mean peak plantar pressure in the feet with transmetatarsal amputation (TMA) than in the intact feet of the same patients. The heels of the amputated feet had significantly lower mean peak plantar pressures than all the forefoot regions. A significantly greater maximum dynamic dorsiflexion range of motion was seen in the intact compared with the TMA feet. However, no difference was noted in the static dorsiflexion range of motion between the two feet and there was, therefore, a trend for the TMA feet to use less of the available range of motion. Given the altered kinematics and elevated plantar pressures noted in this study, careful postsurgical footwear management of feet with TMA would appear to be essential if ulceration is to be prevented.

Aged↗
PubMed1996

In-shoe plantar pressures during activities of daily living: implications for therapeutic footwear design.

Pressures on the plantar surface of the foot during activities of daily living were measured in 12 young, healthy subjects using an in-shoe pressure-measuring device. The tasks chosen were standing, slow and fast walking, slow running, walking up and down stairs, rising from and sitting in a chair, and walking in a circle. All except the sitting tasks showed significantly higher pressures in all regions of the foot compared with standing, with the exception of walking up stairs and walking down stairs in the heel region. Both running and walking in a circle led to higher pressures (up to 1.42 times greater) in the total foot compared with "normal" walking. Furthermore, pressures during other activities were not always well predicted by walking pressures (r2 = 0.10-0.77). Therefore, measurement during level walking alone cannot be considered to fully define the plantar pressure affecting a foot in a particular shoe during activities of daily life.

Activities of Daily Living↗
PubMed1996

A method for the investigation of the effects of outsole modifications in therapeutic footwear.

Experiments to determine the effects of therapeutic shoe outsole modifications frequently require the examination of many different configurations and typically use in-shoe pressure measurement to determine the optimal design. A method is presented here to allow the foot-shoe interface to remain undisturbed as different outsole designs are used in the same patient. A standard extra-depth (or super extra-depth) shoe is modified to house three receptacles for quarter-turn fasteners in a carbon fiber plate. The fasteners pass through the outsole unit and secure it firmly to the plate. Results from a typical experiment are presented to illustrate the effectiveness of the approach. It is possible that a large clinic could use this approach in complex cases to assist with optimal footwear prescription.

Humans↗