Ceramide selectively decreases tau levels in differentiated PC12 cells through modulation of calpain I

Ceramide has been recently proposed to be a signal mediator in several important physiological processes including apoptosis, cellular growth, and differentiation. Because the microtubule-associated protein tau plays an important role in the establishment and maintenance of neuronal morphology, the effects of ceramide on tau were examined. Treatment of differentiated PC12 cells with the cell-permeable ceramide derivative N-acetylsphingosine (C2) resulted in a significant reduction in tau levels. Significant decreases in tau levels were also observed when the cells were treated with another ceramide derivative, N-hexanoylsphingosine (C6). In addition, C2 treatment increased the levels of a calpain-derived spectrin breakdown product but did not alter the levels of two cytoskeletal proteins, alpha-actin and alpha-tubulin. Because both tau and spectrin are proteolyzed in vitro by the calcium-activated cysteine protease calpain, the effects of ceramide analogues on the activity of this protease were examined. Treatment of PC12 cells with C2 enhanced calcium-stimulated proteolytic activity significantly, as revealed by monitoring the hydrolysis of the membrane-permeable calpain-selective fluorescence probe N-succinyl-L-leucyl-L-leucyl-L-valyl-L-tyrosine-7-amido-4-methylcoumarin . This activity increase was not due to a direct effect of C2 on calpains, because C2 did not alter the activities of purified calpain I or II. In addition, C2 treatment of PC12 cells resulted in a significant increase in the levels of calpain I and, to a lesser extent, the levels of calpastatin (an endogenous calpain inhibitor protein), whereas the levels of calpain II were not changed. Moreover, treatment of the cells with the synthetic calpain-specific inhibitor N-carbobenzoxy-L-leucyl-L-leucyl-L-tyrosine diazomethyl ketone blocked the C2-induced decreases in tau levels. These results indicate that tau levels are regulated in response to a physiological factor and, thus, have implications for ceramide-mediated changes in normal and pathological neuronal processes.     

Polymerase chain reaction in the diagnosis of tuberculosis. Comparison of two target sequences for amplification

Amplification of a 340 bp sequence of the 38 kDa protein gene of Mycobacterium tuberculosis by the polymerase chain reaction has been developed. The sensitivity of this PCR was shown to be 10 fg both by agarose gel electrophoresis and Southern blot hybridisation being equivalent to 2-3 organisms and highly specific to M. tuberculosis and excluding even M. tuberculosis H37Ra and Mycobacterium bovis BCG. Sputum samples from patients with pulmonary tuberculosis gave a positivity rate of 45%. PCR was also performed using pt8 and pt9 primers which amplified a 541 bp sequence of IS6110. 41% of the above samples gave positive amplification. Three samples that were positive for 38 kDa sequence were negative for IS6110.     

Is it possible to perform immediate cardiac assist using untrained latissimus dorsi muscle in a work-rest regimen?

The authors investigated what contractile force (CF) could be obtained from unconditioned latissimus dorsi muscle immediately after mobilization and for the 2 week vascular period of recovery. Latissimus dorsi muscle mobilization was performed on seven adult (4 experimental and 3 control) sheep leaving only the pedicle and the peripheral muscle intact. Telectronics stimulators (Myostim 7220; Teletronics Pacing Systems, Inc, Englewood, CO) were implanted. Immediately after mobilization 11-35% of the initial CF was lost. A 30 min fatigue test was performed 1 hr after mobilization (20 g/kg preload, 10 V, 10 Hz, 15 BPM, 6 impulses per burst) using a 1 min work-1 min rest regimen. Two sheep lost 2-12% of initial CF; two increased CF by 14-24%. At the end of the fatigue test, CF consisted of 74-89% of immobilized CF. Electrical stimulation training of the muscle was then initiated with the following regimen in the experimental animals only: 15 BPM, single impulses, 5 V, 10 Hz. Every day the muscle was exercised using a work-rest regimen to mimic cardiac assist, starting with 20 min on day 2, and increasing by 2 min per day until a total of 50 min was reached on day 16. All animals were retested for CF using a 42 min fatigue test on days 6, 11, and 16. On day 6, there was no fatigue evident in the experimental group during the 42 min test. CF after testing was 59-81% (mean 67%) of initial data. In the control group (animals with no electrical stimulation training protocol), CF decreased by 11% (from 64 to 53%). On day 11, there was no fatigue evident in the experimental group; CF in all animals increased by 2-8%. On day 16, there was also no fatigue evident in the experimental group; CF increased by 0-9%. An additional 20 min of continuous contraction (15 BPM) fatigue testing was performed on the muscle without rest between the tests. No fatigue was evident at the end of testing. Light microscopic analysis of latissimus dorsi muscle biopsy specimens taken on the days of testing showed no evidence of necrotic damage. Our investigations suggest that it may be possible to start muscle transformation immediately after mobilization and use the untrained latissimus dorsi muscle for cardiac assist immediately after surgery for short periods.     

The phylogeny of the wrist

BACKGROUND: Long-term results on LASIK are not available to date. We therefore evaluated the predictability, stability and complication rate after LASIK in moderate--to-high myopia. PATIENTS AND METHODS: We treated 70 eyes (41 patients) using the Automatic Corneal Shaper and the Keracor 116 excimer laser. Patients were followed for 1, 6, 12 and 24 months. Spectacle refraction, visual acuity, rate of retreatment, and patient satisfaction were evaluated. RESULTS: At 24 months the results were as follows: Myopia -5 to -9.9 D (n = 18): 94% within 1 D; regression between 1 and 12 (12 and 24) months > 1 D in 6% (6%); uncorrected acuity 20/40 or better in 83%; no loss of 2 ore more lines of visual acuity; 89% highly satisfied. Myopia -10 to -14.9 D (n = 12): 88% within 1 D; regression between 1 and 12 (12 and 24) months > 1 D in 20% (0%); uncorrected acuity 20/40 or better in 72%; 4% lost 2 or more lines of visual acuity; 96% highly satisfied. Myopia -15 to -29 D (n = 22): 33% within 1 D; regression between 1 and 12 (12 and 24) months > 1 D in 41% (18%); uncorrected acuity 20/40 or better in 7%; no loss of 2 or more lines of visual acuity; 67% highly satisfied. CONCLUSION: LASIK is an accurate, effective and stable procedure for correcting myopia of -5 to -10 D. Results are less precise in myopia up to -15 D, and some visual loss occurs in a number of patients. In myopia > -15 D, results are not satisfactory because of poor accuracy and low stability.