ST Depression and Left Ventricular Haemodynamics during Exercise in Patients with Angina Pectoris

ABSTRACT. The mechanism of ischaemic ST depression and the cause of its low sensitivity to coronary artery stenosis are not well understood. Of 30 patients with severe stable effort angina, 19 (63%) showed ischaemic ST depressions after exercise (the STAE group) and 11 did not. The highest load during the symptom-limited exercise test and the heart rate on that load did not differ between the two groups. The clinical characteristics and angiographic findings were also similar, bat the findings at heart catheterization differed during exercise (in supine). Although the load was similar, the stroke index was significantly lower (38 vs. 53 ml/m² BSA) and the left ventricular end-diastolic pressure rose to a significantly higher value in the STAE group (40 vs. 32 mmHg). When STAE occurred, they were exclusively or concomitantly present in chest lead 5. These findings suggest that ischaemic STAE may not reflect regional ischaemia but the consequent left ventricular dysfunction. The mechanism may, for example, be that a sufficiently elevated left ventricular diastolic pressure causes a global subendocardial ischaemia.     

Marginal porosity of light activated composites in relation to use of intermediate low-viscous resins

Abstract – The marginal porosity of four light activated restoratives (Command, Durafill, Prismafill and Silux) was investigated in extracted human teeth It was found that the use of a lowviscous resin prior to application of the restorative materials significantly reduced the marginal porosity in both acid etched enamel cavities and EDTA-cleaned dentin cavities.     

Contraction pattern of composite resins in dentin cavities

Abstract – The correlation between the wall-to-wall polymerization contraction close to the surface and the marginal gap in the deeper parts of chemically cured resin fillings was investigated. The investigation was carried out with fillings placed in non-etched dentin cavities in extracted human teeth. A negative correlation was found; i.e. the narrower the marginal gap in the upper part of the cavities, the more pronounced the contraction in the deeper parts of the fillings, and vice versa.     

Composite wall-to-wall polymerization contraction in dentin cavities treated with various bonding agents

Abstract – Extracted human teeth are frequently used in studies on bonding of composites to dentin. However, little is known about the effect of storing conditions on the results recorded. The purpose of the present work was to measure the wall-to-wall polymerization contraction of a light-cured composite material with and without the use of five different dentin bonding agents in cylindrical dentin cavities prepared in extracted human teeth, either fresh or after storing for up to 4 wk in four different media. No effect of the storing conditions on the width of contraction gaps could be demonstrated when the teeth were stored either in tap water or in a 1.0% aqueous chloramine solution. Aqueous solutions of either 0.1% benzalkonium chloride or 0.9% sodium chloride did occasionally affect the size of the contraction gap.     

Frequent Attacks of Supraventricular Tachycardia in a Patient Treated with an Automatic Scanning Pacemaker (PASAR): Holter Documentation of 554 Episodes

A 68-year-old woman suffering from frequent attacks of supraventricular tachycardia received an implantable, automatic scanning pacemaker for tachycardia termination (PASAR). Electrophysiological study had shown the mechanism to be atrioventricular reentry with retrograde conduction through a concealed bypass tract. During 1 year of follow-up, a total of twenty-one 24-hour Holter recordings documented 554 episodes of tachycardia. In spite of marked fluctuation in tachycardia rate from 135 to 195 bpm and a considerable variation in diurnal pattern of onset of episodes, a clinical improvement resulted. Previous episodes of tachycardia had been isolated and of longer duration. Following implantation, an unexpected observation was made of numerous episodes of supraventricular tachycardia confined to periods lasting up to several hours. This pattern seemed to result from the efficacy of tachycardia termination combined with a continued presence of factors responsible for initiation of tachycardia.     

Nuclear magnetic resonance studies of the C-terminal human growth hormone fragment I179–C182–[SS]-C189-P191 and the related trisulfide peptide I179–C182-[SSS]-C189–P

The synthetic C-terminal hGH fragment I179-C182-[SS]-C189-P191 and the related trisulfide peptide I179-C182-[SSS]-C189-P191 have been studied using homonuclear ¹H-NMR methods and distance geometry calculations. The ¹H-NMR spectra of both the disulfide (diS) and the trisulfide (triS) were completely assigned. Amide proton exchange rates, NOEs and the temperature dependence of the NH chemical shifts indicate a hydrogen bond in triS between Val 185 and Ser 188 stabilizing a turn in this region. ³J_{H, H} coupling constants and NOEs were measured and used as input for distance geometry calculations. For triS two families of structures with averaged pairwise backbone root mean square deviations for Cys 182-Cys 189 of 1.3–1.5 Å were found, only one of which is compatible with experimental data. For diS only one family of structures was found, but with such a low structural definition (backbone rmsd >2Å) that no interpretation into a consensus structure is useful. The generated structures were compared to the crystal structure of the terminal loop in hGH. complexed to its binding proteins. The resemblance was low between the solution structures of the tridecapeptides and the terminal hGH loop. © Munksgaard 1997.     

Activation of the tubuloglomerular feedback mechanism in dehydrated rats

To study the influence of the tubuloglomerular feedback control (TGF) on the regulation of glomerular filtration rate (GFR) during dehydration, micropuncture experiments were performed on surface nephrons of dehydrated rats. Dehydration was achieved by withdrawal of food and water for 24 h. The urine flow rate decreased to 1.5 μl/min (controls 2.9 μl/min) and GFR decreased in these rats to 0.80 ml/min (controls 1.22). TGF was studied by two different micropuncture procedures. With the first technique the changes in proximal stop-flow pressure in response to changes of the late proximal microperfusion rate were measured. With this technique the perfusion rate necessary to induce a half maximal stop-flow pressure response, the turning point, was also determined. An increased TGF sensitivity was found in dehydrated rats, as indicated by increased stop-flow pressure responses (35 versus 26%) and decreased turning points (16 versus 21 nl/min). With the second micropuncture technique the single nephron GFR (SNGFR) was measured at distal and proximal tubular sites, in the same nephron. Distal SNGFR was decreased during dehydration to 32.2 nl/min, versus 42.7 nl/min in controls. A significant difference between paired SNGFR measurements in the same nephron was observed during dehydration, the proximal value being 5.3 nl/min higher than the distal, whereas this difference was not seen in control rats. This finding indicates that activation of the feedback mechanism takes place to reduce SNGFR. It is concluded that the decrease in whole kidney GFR is partly caused by the observed increase in feedback activity. The present results are also in agreement with our earlier hypothesis that the hydrostatic and oncotic pressure conditions within the interstitial space surrounding the macula densa cells modulate the sensitivity of the tubuloglomerular feedback mechanism.     

Bonding of restorative resins to dentin by means of methacryloylchloride and methacryloyl-R-isocyanate

Abstract – The bonding of restorative resins to dentin by means of an intermediary monomer containing a carboxylic acid chloride or an isocyanate group was investigated. Such intermediary monomers are supposed to react with the organic constituent of dentin. Bond strengths were enhanced by the use of the intermediary monomers, resulting in mean bond strengths of 0.13 kg/mm2. Bond strengths of this order of size are probably too low to be of clinical interest.     

Protective value of sympathectomy of the ear in noise

Noise-induced hearing loss was assessed in unilaterally sympathectomized rats exposed one month to 100 dB L_eq(lin) noise. The systolic blood pressure of these animals was in the range of 110–140 mmHg. Auditory sensitivity was determined electrophysiologically by brainstem response audiometry to 1/3-octave filtered clicks. The results showed that the loss of sensitivity was about 10 dB smaller (p<0.01) on the sympathectomized side. This observation may partially explain the individual differences in susceptibility to noise-induced hearing loss and point towards protective measures and therapeutic possibilities through manipulation of sympathetic activity in the inner ear.