In vitro laxity-testers for knee joints of mice

The knee joints of mice can be used as a model for studying the effects of interventions on knee laxity. The goal of this study was to quantify knee joint laxity in vitro. Three devices were developed: a positioning- and cementing device, an anterior-posterior (AP) laxity tester and a varus-valgus (VV) laxity tester. The positioning and cementing device was used to position the joint in a reproducible way and to attach clamping pins to the proximal femur and distal tibia using PM MA. The clamping pins were used to fix the joint to the AP- and VV-testers. In both testers the load was applied by means of a spindle-actuated spring while load and displacements were measured simultaneously. The load--displacement data were used to calculate displacement and compliance parameters. The performance of the testers was evaluated by testing 5 normal knee joints of 5 mice. Total AP-translation at + or - 0.8 N was 0.43 (+ or - 0.16 S.D.) mm with compliances of 0.14 (+ or - 0.05 S.D.) mm N(1) and 0.12 ( + or - 10.05 S.D.) mm N(-1) at 0.8 N posterior and anterior force, respectively. Total VV-rotation at + or - 4 Nmm was 17.2 (+ or - 2.6 S.D.) degrees with compliances of 0.9 degrees Nmm(-1) (+ or - 0.2 degrees Nmm(-1) S.D.) and 1.0 Nmm(-1) (+ or - 0.4 degrees Nmm(-1) S.D.) at 4 Nmm valgus and varus moment, respectively. The contributions of the deformations of the bones and the fixtures to the rotations were negligible in the VV-test. In the AP-test they account for approximately 0.07 ( + or - 0.03 S.D.)mm of the total AP-translation. This will not affect the utilization of the device for comparative analysis. It is concluded that in in vitro evaluation of AP- and VV-laxity in knees of mice is feasible with sufficient accuracy for evaluation of changes after ligament damage.     

Violent emergence from anesthesia: is it a pharmacological or psychological reaction?

A violent emergence from deep sedation is an uncommon reaction in the daily practice of anesthesia in the oral and maxillofacial surgery office. We present a case of a 22-yr-old male with a severe violent emergence from deep sedation that we attribute to a psychological rather than a pharmacological cause. A differential diagnosis is discussed, as are methods of treatment.     

Positive effects of allosteric modulators on the binding properties and the function of muscarinic acetylcholine receptors

Data are reviewed indicating that allosteric modulators can enhance the affinities of muscarinic receptors for their antagonists and agonists, that the enhancement of the affinity for agonists is relevant functionally, and that the allosterically induced conformational change also affects the interaction between the receptors and the G proteins.     

MR of the heart under pharmacologic stress

Magnetic resonance imaging is one method for assessing cardiac function and perfusion at rest and under stress conditions. In this article, the potential of stress magnetic resonance imaging for evaluating ischemic heart disease is reviewed, and technical aspects of some developments that may contribute to comprehensive magnetic resonance imaging assessment of heart disease under rest and stress are discussed.     

Physiological analysis of stress-induced changes in the suppressor activity of mouse T-lymphocytes

BACKGROUND: Despite their potential therapeutic benefit, the effects of cholinergic agents on anal function have been poorly investigated. AIM: To analyse the effects of neostigmine and atropine on anorectal responses to rectal isobaric distension. METHODS: This was a placebo-controlled, randomized, double-blind crossover study, performed in 12 healthy volunteers who received intravenously, on 3 separate days, neostigmine, atropine or the placebo. During each day of the experiment, seven pressure steps (ranging from 1 to 31 mmHg) in three different protocols of rectal isobaric distension (phasic, stepwise and tonic) were applied using an electronic barostat. Manometric responses of the anal canal, adaptative volumes and perception scores of the rectum were recorded. RESULTS: During stepwise distension, a significant drug effect was encountered at the anal level. No drug effect was observed on the other investigated parameters (rectal volumes and rectal perception scores) or for the other modes of distension. Compared to placebo, neostigmine significantly decreased pressures at the upper level of the anal canal for both recto anal inhibitory reflex and mean resting pressures. In contrast, atropine significantly increased pressures at the lower part of the anal canal but did not modify upper anal pressures. CONCLUSION: The present study suggests that cholinergic effects result more from an indirect action on intermediate neurotransmitters and rectal myenteric neurons, than from a direct action on anal targets.