pH and the effect of fluoride and zinc on protein and collagen biosynthesis in rabbit dental pulp in vitro

abstract – The effect of pH in the range 5.6–8.2 on the incorporation of ¹⁴C-proline into the rabbit dental pulp incubated in vitro has been studied. The amount of label in the cold TCA-pool, total protein, and hydroxyproline (i.e. collagen) of the pulp tissue increased linearly with pH in all three fractions. A similar increase was found in the amount of labeled total protein and collagen recovered from the incubation medium. The results indicated that the uptake of ¹⁴C-proline into the TCA-soluble pool was the pH-sensitive step, whereas the incorporation into protein, formation of hydroxyproline, and the release of labeled macromolecules into the medium were not affected to any measurable degree by the ambient pH. In this system, zinc (60 μM) had less effect on the incorporation of ¹⁴C-proline into the different fractions of the pulp tissue at pH 6.6 as compared with pH 7.4, whereas with fluoride (1.3 mM) an increased inhibition of the uptake of ¹⁴C-proline into the TCA-soluble pool and the incorporation into total protein was found upon lowering the pH to 6.8. The inhibitory effect of zinc and fluoride on the release of labeled total protein and collagen into the incubation medium was not affected when the pH was lowered.     

Effect of Electrode Orientation on Lesion Sizes Produced by Irrigated Radiofrequency Ablation Catheters

Background: Irrigated radiofrequency (RF) ablation catheters may produce different lesion sizes dependent upon the electrode orientation to the tissue. This study examined the effect of irrigated electrode orientation on the lesion size and explores a potential mechanism for this effect.
Methods and Results: Lesions were created in isolated porcine myocardium using an open irrigation, closed irrigation, and nonirrigated RF catheter (all 3.5–4 mm tips). Lesions were created with the electrodes with all permutations of electrode orientation (vertical or horizontal), contact pressure (6 or 20 g), and saline superfusate flow (0.2 or 0.4 m/sec) over tissue interface. The effect of electrode irrigation without RF delivery on tissue temperature was assessed with intramyocardial temperature probes and infrared thermal imaging. For both irrigated catheters, the horizontal orientation produced 25–30% smaller lesion volumes than the vertical orientation despite equal or greater power deliveries. The horizontal orientation produced larger lesion volumes for the nonirrigated catheter. Higher superfusate flow rates were associated with decreased lesion volumes for the irrigated catheters but greater lesion volumes for the nonirrigated catheter. Catheter irrigation alone without RF delivery reduced intramyocardial temperatures up to 4.9°C and the horizontal orientation produced a 2-fold greater area of tissue cooling than the vertical orientation.
Conclusion: Horizontal electrode orientations reduce lesion volumes for irrigated RF catheters. This effect may be in part due to greater areas of active tissue cooling in the horizontal orientation.     

Cutaneous Effects of Cryogen Spray Cooling on In Vivo Human Skin

BACKGROUND: Despite widespread clinical use of cryogen spray cooling (CSC) in conjunction with laser dermatologic surgery, in vivo cutaneous effects have not been systematically evaluated. OBJECTIVE: The authors characterize the in vivo cutaneous effects for Fitzpatrick skin types I through VI after CSC exposures of varying spurt durations and spurt delivery patterns (single vs. multiple spurts). MATERIALS AND METHODS: Twenty-seven normal human subjects were exposed to single cryogen spurts from 10 to 80 milliseconds, and multiple spurt patterns consisting of two 20-millisecond spurts, four 10-millisecond spurts, and eight 5-millisecond spurts. Subjects were evaluated by clinical observation and photography at 1 hour, 1 day, and 1, 4, 8, and 12 weeks after CSC exposure. RESULTS: Acute erythema and urticaria (1-24 hours) were noted in 14 of 27 and 3 of 27 subjects, respectively. Transient hyperpigmentation occurred in 4 of 27 subjects (skin types III-VI) but resolved spontaneously without medical intervention in all subjects by 8 weeks. No permanent skin changes were noted in any subjects. Skin reactions were more common with longer single-spurt durations (50 milliseconds or greater) and multiple spurt patterns. CONCLUSION: Acute erythema, urticaria, and, less commonly, transient hyperpigmentation were observed after CSC exposure. Permanent skin injury was not observed and is unlikely.     

Atrial Lead Dysfunction: An Unusual Feature of Hypothyroidism

Hypothyroidism is known to have a multitude of cardiac electrophysiologic effects, including bradycardia, atrioventricular block, prolonged QT interval, and elevated ventricular pacing thresholds. We report the case of a 36‐year‐old woman who presented with isolated dysfunction of her atrial pacemaker lead, which reversed with thyroid hormone replacement.     

Measuring kinaesthetic sensitivity in typically developing children

This study presents a method to quantify a child's sensitivity to passive limb motion, which is an important aspect of kinaesthesia not easily examined clinically. Psychophysical detection thresholds to passive forearm motion were determined in a group of 20 typically developing pre-adolescent children (mean age 12y 6mo, SD 10mo, range 11−13y) and a group of 10 healthy adults (mean age 29y 10mo, SD 10y 7mo, range 18−50y). A newly designed passive motion apparatus was used to measure the time to detection of forearm motion and the errors in determining movement direction. Results showed that limb motion sensitivity became increasingly variable below 0.3°/s in children and adults. In comparison with adults, movement detection times in the pediatric group were increased by between 4% and 108% for the range of tested velocities (0.075−1.35°/s). At 0.075°/s, 5% of the children, but 50% of the adults, made no directional error, indicating that motion perception became unreliable at such low velocity in both groups. The findings demonstrate that sensitivity to passive forearm motion in children should be tested at a range between 0.075 and 0.3°/s. They further suggest that passive motion sensitivity may not be fully developed in pre-adolescent children.     

Congenital Lupus Erythematosus Presenting at Birth with Widespread Erosions, Pancytopenia, and Subsequent Hepatobiliary Disease

Abstract:  Neonatal lupus erythematosus is an uncommon disease caused by transplacental passage of maternal anti-Ro (SS-A), anti-LA (SS-B), or anti-U1RNP antibodies. Cutaneous findings of neonatal lupus are variable, but annular, erythematous plaques occurring within a few weeks of birth are most typical. Cutaneous lesions of congenital onset lupus erythematosus can differ from that of neonatal lupus erythematosus, presenting with atrophy or scarring, and less commonly, erosions. We report an unusual case of congenital lupus erythematosus presenting at birth with widespread erosions, pancytopenia, and subsequent hepatobiliary disease.     

A COMPARISON OF SPATIAL PREDICTION TECHNIQUES FOR AN EXPLORATORY ANALYSIS OF HUMAN CORTICAL MOTOR REPRESENTATIONS

We compare the use of two-dimensional Laplacian smoothing splines and median polish kriging for an exploratory analysis of spatial data sets. Splines were developed originally for modelling a process with determinstic mean structure, while median polish kriging was developed for predicting a spatial random process. We review the fundamentals of both methods, including smoothing parameter selection for splines and variogram estimation and solving the kriging equations for median polish kriging. We demonstrate application of the methods on maps of muscle representations on the human motor cortex (cortical maps). After applying both methods to 20 cortical maps (left and right hemispheres on each of 10 subjects), we compare the fitted surfaces on the basis of predictive ability, aesthetic appeal, and ease of computation. © 1997 by John Wiley & Sons, Ltd.