Biomedical subjects

J Steed

Publications and source records attributed to J Steed.

3 recordsLinked to original sources

PubMed2001

Mouse mast cell secretory granules can function as intracellular ionic oscillators.

Fluorescent Ca2+ probes and digital photo-sectioning techniques were used to directly study the dynamics of Ca2+ in isolated mast cell granules of normal (CB/J) and beige (Bg(j)/Bg(j)) mice. The resting intraluminal free Ca2+ concentration ([Ca2+]L) is 25 +/- 4.2 microM (mean +/- SD, n = 68). Exposure to 3 microM inositol 1,4,5-trisphosphate (InsP3) induced periodic oscillations of luminal Ca2+ ([Ca2+]L) of approximately 10 microM amplitude and a period around 8-10 s. The [Ca2+]L oscillations were accompanied by a corresponding oscillatory release of [Ca2+]L to the extraluminal space. Control experiments using ruthenium red (2 microM) and thapsigargin (100 nM) ruled out artifacts derived from the eventual presence of mitochondria or endoplasmic reticulum in the isolated granule preparation. Oscillations of [Ca2+]L and Ca2+ release result from a Ca2+/K+ exchange process whereby bound Ca is displaced from the heparin polyanionic matrix by inflow of K+ into the granular lumen via an apamin-sensitive Ca2+-sensitive K+ channel (ASK(Ca)), whereas Ca2+ release takes place via an InsP3-receptor-Ca2+ (InsP3-R) channel. These results are consistent with previous observations of [Ca2+]L oscillations and release in/from the endoplasmic reticulum and mucin granules, and suggest that a highly conserved common mechanism might be responsible for [Ca2+]L oscillations and quantal periodic Ca2+ release in/from intracellular Ca2+ storage compartments.

Animals↗

PubMed1997

Correlation between thermosensor temperature and transrectal ultrasonography during prostate cryoablation.

OBJECTIVE: To determine if the adequacy of freezing in the neurovascular bundle region of the prostate during prostate cryotherapy can be monitored by transrectal ultrasonography (TRUS). PATIENTS AND METHODS: The study group consisted of 11 patients undergoing TRUS-guided prostate cryotherapy. The actual temperature in the gland was monitored with thermosensors placed in each prostatic neurovascular bundle. The 2 cryo-operators, working together and blinded to the actual temperature, used sonographic observations to estimate the temperature at the neurovascular bundles every 2 minutes until they believed that the gland was adequately frozen. The congruity between the estimated and measured temperatures was analyzed to determine if the operators could accurately monitor the progress of cryoablation by ultrasonography. RESULTS: There were a total of 85 data points for which the operators thought tumoricidal cryo-injury had been achieved at the neurovascular bundles (temperature -20 degrees C or below). For these points the measured temperature was on average 6.0 degrees C warmer than the estimated temperature (standard deviation, 22). For operator estimates of -20 degrees C or below, the measured temperature was -20 degrees C or below for 37 (44%) data points, between -19 degrees C and 0 degree C for 32 (38%) and greater than 0 degree C for 16 (19%). CONCLUSIONS: The operators were not able to accurately predict subzero temperatures at the neurovascular bundle region by TRUS evaluation. Moreover, the bias and magnitude of the error were significant and might lead to inadequate freezing of the prostate during attempted cryoablation.

Body Temperature↗

PubMed1994

Rating of perceived exertion and blood lactate concentration during submaximal running.

We examined whether the relation between of ratings of perceived exertion (RPE) and exercise intensities associated with the lactate threshold (LT) and blood lactate concentrations (BLC) of 2.5 and 4.0 mM, established with an incremental protocol, held during 30-min treadmill run at constant velocity (V). RPE (11.6, 14.9, 16.8, 18.9), oxygen uptake (VO2) (3.2, 3.7, 3.9, 4.2 l.min-1), and V (168, 196, 215, 227 m.min-1) at LT, BLC of 2.5, and 4.0 mM and peak were determined for nine males during incremental exercise. Subjects then completed three 30-min runs at the V associated with LT and BLC of 2.5 and 4.0 mM, with RPE, VO2, and blood [HLa] determined every 5 min. After min 10 during the 30-min runs, RPE, VO2, and BLC were not significantly different from corresponding values observed during the incremental protocol. Regression equations predicting BLC from RPE were generated from results obtained during the incremental protocol. RPE values from the 30-min runs were used to predict BLC, and the measured BLC was used to validate the use of RPE as a predictor of BLC. Correlations ranged from r = 0.79 to r = 0.98 [total error (TE) ranged from 0.6-1.3 mM]. We conclude that RPE is a physiologically valid tool for prescribing exercise intensity when the intent is to use LT and/or BLC as the intensity criterion.

Adult↗