Hemoglobin near-infrared spectroscopy and surface EMG study in muscle ischaemia and fatiguing isometric contraction.

BACKGROUND: To assess how muscle ischaemia and isometric fatiguing contraction influence oxygen content in striated muscle. METHODS: We simultaneously measured changes in hemoglobin near-infrared (NIR) spectroscopy and in surface EMG before, during, and after muscle ischaemia and ischaemia plus muscle isometric fatiguing contraction. Seventeen healthy male subjects (age range: 19-40 yrs) were examined in our Clinical Neurophysiology Unit. Test I (9 subjects): hemoglobin NIR spectroscopy and stimulated surface EMG were measured for 2 minutes at rest, for 4 minutes during complete ischaemia of tibialis anterior muscle, and for twelve minutes during recovery. Test II (all subjects): hemoglobin NIR spectroscopy and surface EMG were measured for 2 minutes with the subjects performing brief non-fatiguing contractions, for 4 minutes with the subject performing maximal isometric contraction in complete ischaemia, and for twelve minutes during recovery. EMG parameters measured: median density frequency (MDF); muscle fiber conduction velocity (MFCV). NIR spectroscopy parameters measured: percentage of amplitude decrement (% AD) and nadir time (NT) during ischaemia and ischaemic effort; half-recovery time (1/2 RT) from ischaemia effort. RESULTS: At EMG, we observed a significant shift towards lower values of both MFCV and MDF during fatiguing isometric contraction. MDF recovery was faster then MFCV recovery. At NIR spectroscopy, the 1/2 RT slowed a fast pattern in twelve subjects and a slow pattern in five. A significant relationship was found between AD% and 1/2 RT values of test I and AD% and 1/2 values of test II. We found a positive relationship between NT and 1/2 RT in test II. CONCLUSIONS: Surface EMG and hemoglobin NIR spectroscopy can be applied simultaneously to evaluate both fatigue intensity and blood flow changes in striated muscle.

[Lichenoid pityriasis. Immunologic study of 10 children]. / Pitiriasis liquenoide. Estudio inmunológico de diez niños.

Ten children clinically and histologically diagnosed as having pityriasis lichenoides (PL), have been studied by direct immunofluorescence (DIF). Circulating immune complexes (CI) have also been studied in four children. Granular deposits of IgM, located in the walls of the dermal vessels have been observed in two cases, but they have never been found at the dermo-epidermal junction. Granular deposits of C3 have been observed in three children, both in the walls of the dermal vessels and at the dermo-epidermal junction. The search for immune complexes gave negative results in all cases. The hypothesis of some authors that PL is an immune complex disease cannot be confirmed by our findings.