The mechanical behaviour of a novel mammalian intervertebral joint

The mechanics of mammalian intervertebral joints are complicated by the viscoelastic nature of the connective tissues joining vertebrae, and by multiple vertebral articulations and complex morphologies. Further, interspecific variation in these structures can greatly compound their functional variation between species, making comparative mechanical analyses even more difficult. Despite these sources of variation however, mammalian intervertebral joints universally exhibit a creep relaxation behaviour based on the viscoelastic nature of the soft tissue joint. We have evaluated, in 6 degrees of freedom, the mechanical signature of a novel mammalian lumbar intervertebral joint found in the Scutisorex spine, and compared it with a more typical mammalian joint in the Rattus (rat) lumbar spine. Scutisorex , the hero shrew, is an East African species of shrew with what is likely the most highly modified vertebral morphology in the entire history of mammals. Thus we decided to evaluate the mechanical behaviour of the intervertebral joint of this species, comparing it with a more representative mammal species in Rattus . We built a custom, 6 degrees of freedom, intervertebral joint transducer and a combined axial moment and load application system in order to quantify and compare the complex mechanical behaviour of these joints. Our results suggest that the Scutisorex joint is 5 times more resilient to simple axial torsion per body mass unit than Rattus , and that the complex load (combined axial compression and torsion) mechanical signature of Scutisorex is probably novel among all mammalian intervertebral joints. Under significant but physiological axial compression the Scutisorex intervertebral joint demonstrates no creep relaxation behaviour, simulating the mechanical behaviour of a rigid construct rather than a viscoelastic joint. The purpose of this rigid intervertebral joint in the ecology of Scutisorex remains unknown.     

Determinants of Left Ventricular Functional Recovery After Thrombolytic Therapy and/or Immediate Coronary Angioplasty in Acute Myocardial Infarction

To determine the effect of thrombolytic therapy and/or immediate coronary angioplasty (PTCA) on left ventricular function, 129 patients with acute transmural myocardial infarction were retrospectively studied. Treatment strategies included thrombolytic therapy alone (n = 29), PTCA alone (n = 41), and combined thrombolytic therapy and PTCA (n = 59). Left ventricular ejection fraction (LVEF) and infarct zone regional wall motion (RWM) were determined from contrast ventriculography obtained acutely and at day 7–10. In the overall group, there was a 2 ± 9% increase in LVEF (p < 0.02) and a 0.7 ± 1.2 SD/chord increase in RWM (p < 0.0001) between day 1 and day J-10. Patients with a patent infarct vessel at day 7–10 had a more significant change (Δ) in LVEF (3 ± 8 vs ?5 ± 9%, p = 0.0002) and RWM (0.8 ± 1.2 vs 0.1 ± 1.0 SD/chord, p < 0.02) than patients with an occluded vessel. Patients with a residual stenosis < 70% at day 7–10 manifested a greater ΔLVEF (3 ± 8vs-5 ± 9%, p < 0.01) and ΔRWN (0.9 ± 1.2 vs 0.1 ± 1.0 SD/ chord, p < 0.05) than patients who were occluded. There was a negative correlation between residual stenosis and ΔRWM (p < 0.04). Patients treated < 3 hours after symptom onset demonstrated a more significant ΔRWM when compared to patients treated ≥ 3 hours (1.0 ± 1.3 vs 0.5 ± 1.1 SD/chord, p < 0.04). Patients treated with combined thrombolytic therapy and PTCA were observed to have a greater ARWM than patients treated with thrombolytic therapy alone (0.8 ± 1.2 vs 0.2 ±0.9 SD/chord, p < 0.05). Patients with an LVEF > 40% demonstrated a more significant ΔLVEF than patients; ± 40% (7 ± 8vs 1 ± 8%, p < 0.007). A significant improvement in ΔLVEF was noted only in patients with an anterior infarction when compared to patients with an inferior infarction. Age, sex, presence of multivessel disease, history of prior myocardial infarction, initial patency of the infarct vessel, and presence of collaterals had no effect on left ventricular function. Stepwise multiple regression identified residual stenosis, time to treatment, and the degree of initial global impairment as the major joint predictors of ventricular functional recovery. (J Interven Cardiol 1988:1:3)     

Radiofrequency Current Application on Immature Porcine Atrial Myocardium: No Evidence of Areas of Slow Conduction After 12-Month Follow-Up

Electrophysiologic Sequelae 12 Months After Radiofrequency Current Application. Introduction : Radiofrequency current (RFC) application is a widely used procedure for treatment of supraventricular arrhythmias. The purpose of this study was to investigate late electrophysiologic sequelae of RFC lesions at immature atrial myocardium in pigs, as they have not yet been systematically investigated in vitro.
Methods and Results : RFC application (temperature guided) was performed in seven piglets (mean age 6 weeks) by a steerahle 6-French electrode catheter positioned at the lateral aspect of the tricuspid valve annulus. After 12 months, hearts were removed, and lesions with surrounding tissue were isolated. The viable tissue at the border of the specimen was paced with a cycle length of 500 and 600 msec. One hundred fifty impalements were performed on each specimen using capillary microelectrodes to record action potential characteristics from the lesion's surface and the surrounding tissue. In all seven specimens, no transmembrane action potentials from the fibrotic surface of each of the lesions could be recorded. The surrounding viable tissue was sharply demarcated electrically. No areas of slow conduction were detected. Action potential characteristics as mean maximum diastolic transmembrane potential, mean action potential duration at 90% repolarization, and upstroke velocity of phase 0 of the action potential were all normal.
Conclusion : No evidence of areas of slow conduction 12 months after RFC application at immature atrial myocardium suggests that this technique is safe regarding occurrence of late atrial tachyarrhythmias after the procedure.     

Punch-biopsy of minor salivary glands in the diagnosis of Sjögren's syndrome

Abstract— The aim of the present investigation has been to examine whether the histopathologic changes in the minor salivary glands in patients with Sjögren's syndrome are of the same nature as the changes in the major salivary glands. Punch-biopsies were taken from the lower labial mucosa in 14 patients; 12 of these had a verified Sjögren's syndrome. In 10 patients changes in accordance with those of a benign lymphoepithelial lesion were present in the minor salivary glands. The technique was found valuable in the diagnosis of general disorders with salivary gland involvement.