Biomedical subjects

J C Marigold

Publications and source records attributed to J C Marigold.

22 records · Page 2Linked to original sources

PubMed1979

A microwave heating system for improving temperature uniformity in heated tissue.

A microwave heating system, designed to improve temperature uniformity in heated tissue, is described. The system employs parallel-opposed waveguide applicators, operating in the TE10 mode at 2450 MHz with the tissue to be heated (i.e. mouse intestine) immersed in a liquid which is both biologically compatible with and dielectrically similar to the tissue. The liquid improves the microwave coupling and avoids shape and size dependent absorption characteristics of the irregularly shaped tissue. Also, by maintaining this liquid at a suitable temperature with respect to that required in the tissue, the thermal losses and hence temperature gradients in the tissue are reduced compared with heating in hot liquid alone.

Animals↗

PubMed1979

The effect of local hyperthermia on the small intestine of the mouse.

Small loops of mouse jejunum were exteriorized and heated by immersion in a bath of Krebs-Ringer salt solution. Crypts were lost in the heated regions with a half-time of approximately six hours and reached a steady level of damage by 10--16 hours. There was no recovery in crypt number for one week after hyperthermia. Using a 24 hour assay, crypt survival curves were obtained using various heating times in the temperature range 37.5 degrees C--44.5 degrees C. These curves were qualitatively similar to those resulting from radiation damage, showing a shoulder followed by exponential killing. As the temperature was increased, progressive changes in shape of the curves indicated a proportional inhibition of accumulation of sublethal heat damage combined with increased rate of expression of lethal damage. Over the temperature range 42.3 degrees C--44.5 degrees C, a linear relationship was found between the rate of crypt loss and the reciprocal of the absolute temperature. An activation energy of 600 +/- 70 kJ mole-1 was calculated using the Arrhenius equation. In this temperature range, doubling the heating time had the same effect as increasing the temperature by 1 degree C. At temperatures below about 42.3 degrees C, the tissue became relatively less sensitive to increasing the treatment time.

Animals↗

PubMedDate not supplied

The effect of step-down heating on mouse small intestinal mucosa.

Step-down heating (SDH) was investigated in mouse small intestine by giving a primary (conditioning) treatment at or above 43 degrees C followed by a test treatment below 43 degrees C. Crypt dose-response curves following SDH were compared with those obtained using the test treatment alone; the SDH effect was characterized by a reduction in shoulder (an additive effect) and an increase in slope (thermosensitization). The thermosensitization ratio, defined as slope SDH-heated/slope single-heated, was independent of the conditioning temperature but increased to a maximum of approximately three as the duration of conditioning increased. Thermosensitization was eliminated when the conditioning treatment was itself sufficient to cause significant crypt loss and, also, when the interval between the two treatments was 0.5 h or longer. This period was less than that required for either recovery of the 'shoulder' on the crypt dose-response curve or the development of thermotolerance following the primary treatment. Thermotolerance which develops in intestine during prolonged hyperthermia (after approximately 100 min) was not affected by SDH and Arrhenius analysis indicated that the activation energy for temperatures below 43 degrees C was not significantly altered by SDH. In summary, the SDH effect on small intestine, assessed using the crypt loss endpoint, was similar to thermosensitization observed in vitro. However, the lower magnitude of the effect and its complex dependence on the primary heat treatment suggest either that crypt cells respond to SDH in a unique and characteristic manner or that the crypt assay in vivo and reproductive survival in vitro do not reflect the same endpoint.

Adaptation, Physiological↗

PubMedDate not supplied

Thermosensitization by step-down heating in mouse testis.

Step-down heating (SDH) was investigated in mouse testis by giving an initial treatment of 3 min at 43.0 degrees C followed immediately by a treatment in the temperature range 38.0-42.0 degrees C. The dose-response curves for testis weight loss as a function of duration of hyperthermia were compared with those obtained using single-temperature treatments. In all cases the curves were linear, allowing the use of Arrhenius analysis. For single-temperature treatments the Arrhenius relationship showed an inflection at approximately 41 degrees C with a small, but significant, increase in activation energy for hyperthermal temperatures below the transition. SDH increased the thermal sensitivity in this lower range, by approximately 1 degree C, but the activation energy was not significantly altered. The results support the view that in vivo thermosensitization by SDH is not due solely to inhibition of development of thermotolerance.

Animals↗