The superiority of maximum fiber elastance over maximum stress-volume ratio as an index of contractile state

The end-systolic pressure-volume relationship has been used as a load-independent measure of ventricular pump performance. Since comparisons of load between ventricles of different size and thickness may be more accurately made with measurements of wall stress than with those of pressure, the end-systolic stress-volume relationship at one or more levels of end-systolic stress has been used to estimate contractile function in hypertrophied ventricles. Linear regression of end-systolic stress against end-systolic volume for differently loaded beats has a slope termed maximum fiber elastance (fiber Emax) and a volume intercept termed Vo; the maximum stress-volume ratio (MSVR) for a single beat is an approximation of fiber Emax but assumes Vo = 0. However, the influence of preload, afterload, and inotropic state on these indexes has not been examined. We therefore studied the stress-volume relationship in seven open-chest dogs instrumented with ultrasonic crystals and micromanometers. Postextrasystolic potentiation (PESP) increased both the MSVR (5.7 +/- 1.83 vs 4.85 +/- 1.43 at control, p less than .05) and fiber Emax (13.93 +/- 3.24 vs 9.24 +/- 2.15 at control; p less than .05). Augmentation of preload by infusion of dextran, with the use of nitroprusside to maintain afterload relatively constant, did not significantly influence either the MSVR or fiber Emax. Vo was not significantly influenced by PESP, but was shifted to higher values by augmentation of preload (17.5 +/- 14.8 vs 13.9 +/- 11.1 ml at control; p less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Nonlymphomatous metastatic tumor to the testis

A patient with pancreatic carcinoma presented with an initial left testicular mass that proved to be metastatic adenocarcinoma of the pancreas. Regional spread of the pancreatic carcinoma may have created venous and lymphatic obstruction with inferior passage of tumor emboli to the testis. A summary of nonlymphomatous secondary tumors of the testis also is presented.

Electroacupuncture treatment of morphine-dependent mice reduces signs of withdrawal, without showing cross-tolerance

Morphine pellets (75 mg morphine base per pellet) were implanted subcutaneously in mice (B6AF1/J) and were surgically removed after 3 or 8 days. During morphine abstinence (7 h after pellet removal), the mice were treated with electroacupuncture (EA). The results indicate that EA analgesia shows no cross-tolerance to morphine. Additionally, EA reduced withdrawal behaviour (jumping) in 50% of the mice during morphine abstinence.

Relationship between diazepam dose, plasma level, age, and central nervous system depression

Patients undergoing elective cardioversion for treatment of arrhythmias were premedicated with diazepam. The dose was individualized to achieve a degree of central nervous system CNS) depression characterized by response to painful but not vocal stimulation. Promptly following each cardioversion, blood was drawn and the plasma diazepam concentration was measured by gas chromatography. The plasma levels varied as widely as the diazepam doses so that there was no fixed plasma level of diazepam associated with the degree of CNS depression produced in these patients. However, both the dose of diazepam and the resulting plasma level were inversely correlated to age, indicating that age is a critical factor in the use of diazepam for cardioversion premedication; elderly are more sensitive to the depressant effects of this drug than the young.

Sensitization to cocaine stimulation in mice

Repeated administration of cocaine to B6AF1/J mice increased their running response to 20 mg/kg cocaine as much as four-fold over the response to the first injection. After four daily injections, the extent of the increase was proportional to the dose of cocaine that was used for pretreatment. Sensitization persisted for as long as 2 months after the last injection of cocaine. Cocaine-pretreated mice did not show an increased running response to either morphine or d-amphetamine. The response to cocaine was increased two-fold by treatment with morphine and three-fold by pretreatment with d-amphetamine. Pretreatment with either imipramine or reserpine did not produce sensitization to cocaine. There was no correlation between cocaine sensitization and whole-brain catecholamine levels. There were marked differences in both the running response to cocaine and the extent of cocaine sensitization betwee the parental strains, C57B1/6J and A/J. Experiments with recombinant-inbred lines, derived from C57B1/6By and BALB/cBy mice, suggest that the initial response to cocaine and the development of sensitization are controlled by different genetic determinants.

A genetic analysis of the response to morphine in mice: analgesia and running

Two progenitor strains, BALB/cBy and C57BL/6By, their reciprocal F1 hybrids, and seven of their recombinant-inbred derived lines were used to examine the genetic basis of the response to thermal pain, and morphine analgesia at doses of 2.5, 5.0 and 10.0mg/kg. Both the latency of response to thermal pain and the analgesic response differed significantly among the various strains tested. Strong genetic determinants appear to control their responses. Analyses of the data did not permit clarification regarding the linkage of these determinants. Photoelectric activity cages were used to test the running response of the same strains to 12.5, 25 and 40 mg/kg morphine sulfate. The genetic determinants for running activity were different from those for analgesia. There is clear evidence for two or more loci controlling the behavior at 60 and 75 min after injection, but not enough information to define the loci involved.

Increased running response to morphine in morphine-pretreated mice

The running response of B6AF1/J mice to 25 mg/kg of morphine sulfate was increased up to 3-fold when this dose was administered either twice daily for 5 days or once a week for 2 or 3 weeks. The effect of weekly pretreatment was proportional to the dose of morphine and lasted as long as 1 month after pretreatment was stopped. There was no sensitization when the mice were less than 15 days old at the time of pretreatment. Of the parental strains, untreated C57Bl/6J mice showed a good running response to morphine, while A/J mice showed little response. Pretreatment of either of these strains produced only slight sensitization. Pretreatment of the hybrids with levorphanol increased the response to morphine. Dextrorphan and naloxone were ineffective. Sensitization by morphine was blocked by naloxone. Increased morphine running was not associated with analgesic tolerance as measured by the tail-flick assay. Morphine pretreatment produced some increase in the running response to amphetamine and to cocaine. Pretreatment with amphetamine or cocaine did not increase the response to morphine.