A statistical assessment of the dependability of transcutaneous tissue oxygen tension measurements

Transcutaneous oxygen tension measurements (PtcO2) were obtained for subjects in two groups: peripheral vascular patients (N = 15) and disease-free controls (N = 9). Readings were taken in each of three locations, arm, knee and foot, in supine and erect positions, at fixed and random times, on each of 3 consecutive days. The dependability (the proportion of true variance in total variance) of PtcO2 measurements was evaluated using a generalizability model. The preliminary generalizability study analysis indicated that day-to-day variation of PtcO2 level was larger than within-day variation. Therefore, in order to decrease the measurement error variance one would preferably increase the number of days for measurements (nd) rather than increase the number of measurements within each day (nt). A decision study analysis was also performed which resulted in estimates of error variance and two interdependent dependability measures: dependability coefficients (DCs) and signal to noise ratios (S/Ns). PtcO2 dependability values were generally different for the two groups. Cases had high DCs and S/Ns (DC greater than or equal to 0.9, S/N greater than or equal to 9) in all location-position combinations except for arm measurements. On the other hand, controls had low and unacceptable DCs and S/Ns (DC less than 0.8, S/N less than 4) in all location-position combinations. Cases and controls had generally lower dependability values when PtcO2 ratios were analyzed. The only two ratio-position categories for which dependability values were in the acceptable range (DC greater than or equal to 0.8, S/N greater than or equal to 4) were foot/arm erect and foot/arm supine for the cases.(ABSTRACT TRUNCATED AT 250 WORDS)     

Possible roles of microfibrils in elastogenesis

On examination in the electron microscope elastic tissue is seen to consist of an amorphous component surrounded by microfibrillar components. The exact relationship between these components is unknown, although during development the microfibrils appear before the amorphous material. In this report we summarize our recent observations on the microfibrillar material. At high magnification the microfibrils are seen to have a poorly staining central core around the periphery of which are arranged more densely staining filaments which appear to wind around the microfibrils in a spiral fashion. Careful measurements of microfibrillar diameters from the aorta of four large species show that there are significant differences in the mean diameter and population distributions with species. The mean diameter of the microfibrils changes with age during fetal and postnatal development. The results of immunoelectronmicroscopic localization of an antibody to a microfibrillar component are reported and the possible roles of microfibrils in elastic tissue formation are examined.     

Barbital alteration of central nervous system sensitivity to hexobarbital in the rat

Alteration in central nervous system (CNS) sensitivity to the hypnotic effect of the hexobarbital was assessed by analytical, electroencephalographic, and pharmacokinetic techniques in barbital-treated rats. Each of these conceptually diverse experimental methodologies yielded similar conclusions concerning the alteration of CNS sensitivity by barbital treatment.