Biomedical subjects

M R Menard

Publications and source records attributed to M R Menard.

7 recordsLinked to original sources

PubMed1992

Serial lumbar dynamometry in low back pain.

To determine the significance of changes in motor performance as measured by lumbar dynamometry, serial lumbar dynamometry was performed on a group of 45 male Workers' Compensation patients with chronic "mechanical" low back pain and in a group of 20 healthy male volunteers. The patients were men aged 20-60 years, whose current episode of low back pain had lasted for at least 3 months (mean 19.5 weeks, range 12-47 weeks). Testing was performed at entry into a "back school" program of therapy and again 2 weeks and 4 weeks later. The control group showed a slight improvement in almost all variables of strength and range of motion between the first and second tests but no significant change between the second and third tests. This was consistent with a learning effect. The patient group was analyzed as a whole and also in two groups based on their response to the Waddell maneuvers at entry: Waddell score 0-2 (no excessive illness behavior) and 3-5 (excessive illness behavior). As a whole, the patients showed significant progressive improvement in most variables on successive tests. The group with the low Waddell score had significantly greater strength and range of motion than the group with the high Waddell score but the trend of improvement with time was similar in the two groups. The authors conclude that in this sample of patients with low back pain, serial lumbar dynamometry reveals a progressive improvement in performance, which is greater than the improvement expected from the natural history of physical recovery and greater than the improvement expected from an increase in strength and range of motion attributable to the therapeutic exercises performed and is much larger than any learning effect related to the test procedure.

Adult↗

PubMed1992

MELAS syndrome with mitochondrial tRNA(Leu)(UUR) mutation: correlation of clinical state, nerve conduction, and muscle 31P magnetic resonance spectroscopy during treatment with nicotinamide and riboflavin.

We report a patient with mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes treated with riboflavin and nicotinamide for 18 months, during which time previously frequent encephalopathic spells ceased. To confirm clinical benefit, we withdrew treatment and monitored response with muscle 31P magnetic resonance spectroscopy (MRS) and sural nerve conduction studies. Of three prospectively chosen MRS variables, two changed coincidentally with clinical end points; phosphocreatine (PCr)/adenosine triphosphate recovery rates fell in parallel with sural nerve sensory amplitudes, and a drop in muscle bioenergetic efficiency (relationship of inorganic phosphate/PCr to the accelerating force of contracting muscle) coincided with development of encephalopathy. Investigations revealed a deficiency of respiratory complex I and mutation of the mitochondrial tRNA(Leu)(UUR). We suggest that a defective cellular energy state in mitochondrial disease may be partially treatable and that changes seen in appropriate muscle spectroscopy studies may parallel improvement in brain and peripheral nerve function.

Adult↗

PubMed1992

Comparative biomechanical analysis of energy-storing prosthetic feet.

Gait analysis was performed on eight men who had unilateral traumatic below-knee amputation and on nine control subjects. Each subject was given two prostheses--the Seattle Foot and the Flex Foot--which differed only in the energy-storing foot component. Analysis of subjects consisted of clinical gait observation, forceplate analysis of the ground reaction force (GRF) while using each prosthesis during level walking at the natural cadence, and evaluation of subject preference between the two prosthetic feet. In the control subjects, there was no significant asymmetry in any averaged GRF patterns or parameters. In the subjects with amputations, the amputated limb had a weaker propulsion and the nonamputated limb had a stronger propulsion than controls. This was true for both prostheses. During ambulation with the Flex Foot, there was a pattern of larger late vertical forces but smaller late anteroposterior and mediolateral forces. This is consistent with a medial heel whip, and it was observed when the Flex Foot was used. Three months after the biomechanical studies, four subjects used the Flex Foot exclusively, two used the Seattle Foot exclusively, and two used both, ie, the Flex Foot for sports and the Seattle Foot for work. Application of these results to the choice of prosthetic components is discussed.

Adult↗

PubMed1991

Relative metabolic efficiency of concentric and eccentric exercise determined by 31P magnetic resonance spectroscopy.

To determine the relative metabolic efficiency (metabolic energy used per unit of mechanical energy output) of negative to positive muscular power, we used 31P magnetic resonance spectroscopy to monitor the cellular energy metabolism of limb muscles in eight healthy subjects during a nonfatiguing, mixed concentric-eccentric activity and during its concentric and eccentric components. We also studied isometric contractions. We found that in terms of the flow of metabolic energy through the muscle cells, the cost of concentric exercise at this intensity was proportional to the mechanical power generated, but the cost of eccentric and isometric exercise did not increase significantly as the apparent intensity of the exercise increased over the range studied. Although the pattern was similar in all subjects, the quantitative relationship between metabolic cost and mechanical output was different in subjects with different muscular strength. The qualitative results can be explained in the context of the known biochemistry and biophysics of the cellular contractile apparatus (sliding filament theory, with independent force generators).

Adult↗

PubMed1991

Anemia after traumatic spinal cord injury.

The incidence and natural history of anemia in patients with spinal cord injuries (SCI) were investigated in a prospective study of 68 patients consecutively admitted to a regional acute SCI unit. Fifty had SCI and 18 had spine injuries (SI) without neurologic deficit. Thirty-six of 41 males (88%) and six of nine females (67%) with SCI were anemic on at least one occasion. In the first two weeks after injury, in females and in males, there was no significant difference in mean hemoglobin level between SI and SCI patients. At six weeks, no male with SI was anemic, and males with SCI had significantly lower mean hemoglobin levels than those with SI (121.6 g/L vs 145.4 g/L, p less than .001). Identified early causes of anemia were blood loss due to bony soft tissue or visceral injury, gastrointestinal bleeding, and surgery. In the postacute phase (more than six weeks after injury), anemia occurred in 25 of 41 male and three of nine female SCI patients, and its occurrence was associated with the presence of an identified chronic disease, especially urinary tract infection.

Adult↗

PubMed1978

Evaluation of the DMO method for measuring intracellular pH.

Intracellular pH in single muscle fibres from Balanus nubilus was determined, both by the weak acid distribution method (using 5,5-dimethyl-2,4-oxazolidine dione) and by means of a glass pH microelectrode, following prolonged equilibrations in normal, acid or alkaline Ringer solutions. In the DMO method [3H]inulin was combined with [14C]DMO so that an extracellular space could be calculated for each 'DMO space' on each fibre. Less than ideal uptake curves were obtained both for [14C]DMO and [3H]inulin, yet the calculated pHi compared favourably with the microelectrode pHi, especially when the DMO-pHi was calculated from [14C]DMO and [3H]inulin values obtained by extrapolating the 'plateaus' of the uptake curves to time zero. The Waddell and Butler equation was examined to determine why acceptable pHi values should be forthcoming from less than ideal uptake data.

Acid-Base Equilibrium↗

PubMed1976

Intracellular pH of single crustacean muscle fibres by the DMO and electrode methods during acid and alkaline conditions.

1. The intracellular pH of intact single muscle fibres of the giant barnacle was measured directly with a glass micro-electrode following prolonged (2-5 hr) equilibration in one of three solutions: normal Ringer, CO2 Ringer and NH4+ Ringer. 2. The intracellular pH of identically-prepared fibres from the same specimen was measured indirectly from the distribution of DMO following prolonged equilibration in the same solutions. 3. The DMO-pH compared favourably with the electrode-pHi provided DMO-pHi was calculated from the values of the indicator compounds, [14C]DMO and [3H]inulin, obtained by extrapolating the slow uptake phase to time zero. 4. Following prolonged equilibration, the transmembrane H+ ion distribution was found to vary with the membrane potential but not in accordance with a simple Gibbs-Donnan equilibrium. 5. A model which recognizes the existence of two independent net fluxes for H+ across the membrane in developed to explain the results. One of the fluxes represents passive diffusion and the other represents the so called H+-pump. The model predicts the H+-pump rate increases by two orders of magnitude when pHi is reduced from 7-2 to 6-7.

Animals↗