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Biomedical subjects

M R Menard

Publications and source records attributed to M R Menard.

24 records · Page 2Linked to original sources

External application of antibiotic to improve survival of adult laboratory frogs (Rana pipiens).

Survival data for over 500 adult frogs (393 Rana pipiens, 35 Rana clamitans , and 97 Rana temporaria) obtained from commercial suppliers were accumulated. Frogs which developed signs of red-leg disease while being kept in 0.15% saline were cured by addition of appropriate antibiotics to the saline. The appropriate antibiotic was determined by sensitivity testing of bacteria isolated from the sick frogs. When many frogs in a shipment were sick, prophylactic treatment of the entire shipment improved the overall survival in the shipment.

Animals↗

The influence of "nonmyoplasmic" sodium on the measured value of the sodium efflux from barnacle muscle.

In single striated muscle cells of the giant barnacle Balanus nubilus, the sodium content of the myoplasm was measured with an intracellular microelectrode, and the total sodium content of the cell was measured by flame photometry, during immersion of the cells in sodium-free solution. The sodium content of the myoplasm declined slowly but steadily from ca. 10 mmol/kg water to ca. 4 mmol/kg water during immersions lasting up to 16 h. The "nonmyoplasmic" sodium content of the cells, defined as the sodium content after subtraction of the sodium in the extracellular (sorbitol) space and in the myoplasm, declined rapidly from ca. 15 mmol/kg water to ca. 3 mmol/kg water during the first 30 min of immersion in sodium-free solution, but remained constant thereafter. The rapidly lost portion of the nonmyoplasmic sodium (ca. 123 mmol/kg water) was ascribed to the extracellular space but the location of the inexchangeable portion was not discovered. The behavior of the efflux of 22Na which was loaded into the myoplasm by microinjection was consistent with this interpretation. It was concluded that the nonmyoplasmic sodium does not have an appreciable influence on the measured value of the sodium efflux from the myoplasm of barnacle muscle cells.

Animals↗

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↗

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↗

Chopart prosthesis and semirigid foot orthosis in traumatic forefoot amputation. Comparative gait analysis.

Gait was analyzed in seven otherwise healthy males at least 11 mo after they had recovered from a traumatic unilateral transmetatarsal amputation incurred during the course of their usual occupation. All seven were fitted with a semirigid foot orthosis. Four were also fitted with a Chopart prosthesis. Gait was evaluated with forceplate measurements of ground reaction force during free walking, by clinical observation of such ambulation on videotape, and by the subjective impression of the men as obtained by a questionnaire. In all men, with unmodified footwear, with the orthosis, and with the prosthesis, the forceplate data showed an abnormal pattern characterized by reduced stance duration and deficient forward propulsion on the amputated side. The abnormality and asymmetry of ground-reaction forces were less with greater preserved stump length and for a given stump length were with the above-ankle concept (Chopart) prosthesis than with the below-ankle concept. These features were recognized during the clinical analysis of all footwear, but there was an extra irregularity of weight progression noted with the fixed ankle of the Chopart prosthesis. The questionnaire reported stump problems to be the principal difficulty, and the follow-up revealed persistent attempts at surgical management including consideration of amputation at a higher level. It was concluded that the patient and the surgeons are likely to choose preservation of limb length over considerations of function during acute care and that the prosthetic concept best suited to deal with the resulting stump should emphasize unloading the distal part of the stump and smoothing out the impulsive force peak on the stump in late stance to minimize pain and to enhance ambulation capacity.

Adult↗

Direct measurement of sodium influx in vascular smooth muscle. Stimulation by aldosterone.

The influx of 22Na into the smooth muscle cells of incubated rat tail arteries was measured directly, in the presence and absence of 2.8 X 10(-7) M D-aldosterone. During the analysis, extracellular 22Na and 23Na were removed by incubation of the tissue in sodium-free lithium-substituted physiological salt solution at less than 3 degrees C. Aldosterone increased the influx rate coefficient by 10% (0.104 +/- 0.004 [SE] min-1, n = 13, vs 0.095 +/- 0.003 [SE] min-1, n = 13 without aldosterone; p less than 0.01) but did not significantly reduce the sodium content. We conclude from direct measurements that aldosterone acts to increase the influx of sodium in incubated tail arteries from normal rats; we conclude from measurements of the sodium influx and sodium content that aldosterone also acts to increase the efflux of sodium in this preparation.

Aldosterone↗