[Studies on localized low-risk prostate cancer : Do we know enough?] / Studien zum lokal begrenzten Niedrigrisikoprostatakarzinom : Wissen wir genug?

BACKGROUND: Treatment of localized low-risk prostate cancer (PCa) is undergoing a paradigm shift: Invasive treatments such as surgery and radiation therapy are being replaced by defensive strategies such as active surveillance (AS) and watchful waiting (WW). OBJECTIVE: The aim of this work is to evaluate the significance of current studies regarding defensive strategies (AS and WW). METHODS: The best-known AS studies are critically evaluated for their significance in terms of input criteria, follow-up criteria, and statistical significance. RESULTS: The difficulties faced by randomized studies in answering the question of the best treatment for low-risk cancer in two or even more study groups with known low tumor-specific mortality are clearly shown. Some studies fail because of the objective, others-like PIVOT-are underpowered. ProtecT, a renowned randomized, controlled trial (RCT), lists systematic and statistical shortcomings in detail. CONCLUSION: The time and effort required for RCTs to answer the question of which therapy is best for locally limited low-risk cancer is very large because the low specific mortality rate requires a large number of participants and a long study duration. In any case, RCTs create hand-picked cohorts for statistical evaluation that have little to do with care in daily clinical practice. The necessary randomization is also offset by the decision-making of the informed patient. If further studies of low-risk PCa are needed, they will need real-world conditions that an RCT can not provide. To obtain clinically relevant results, we need to rethink things: When planning the study, biometricians and clinicians must understand that the statistical methods used in RCTs are of limited use and they must select a method (e.g. propensity scores) appropriate for health care research.

A novel type of semi-active jet turbulence grid.

This article describes a novel approach to generate increased turbulence levels in an incoming flow. It relies on a cost-effective and robust semi-active jet grid, equipped with flexible tubes as moving elements attached onto tube connections placed at the intersections of a fixed, regular grid. For the present study, these flexible tubes are oriented in counter-flow direction in a wind tunnel. Tube motion is governed by multiple interactions between the main flow and the jets exiting the tubes, resulting in chaotic velocity fluctuations and high turbulence intensities in the test section. After describing the structure of the turbulence generator, the turbulent properties of the airflow downstream of the grid in both passive and active modes are measured by hot-wire anemometry and compared with one another. When activating the turbulence generator, turbulence intensity, turbulent kinetic energy, and the Taylor Reynolds number are noticeably increased in comparison with the passive mode (corresponding to simple grid turbulence). Furthermore, the inertial subrange of the turbulent energy spectrum becomes wider and closely follows Kolmogorov's -5/3 law. These results show that the semi-active grid, in contrast to passive systems, is capable of producing high turbulence levels, even at low incoming flow velocity. Compared to alternatives based on actuators driven by servo-motors, the production and operation costs of the semi-active grid are very moderate and its robustness is much higher.

[Hemorheologic changes in ankylosing spondylitis]. / Hämorheologische Veränderungen bei ankylosierender Spondylitis.

In nineteen patients with a definite ankylosing spondylitis haemorheological parameters were measured: serum, plasma and whole blood viscosity, haematocrit, red cell flexibility and aggregation, fibrinogen and ESR. Compared to matched controls these variables were significantly altered in patients. The pathophysiological meaning of this finding is as yet unclear and needs further investigation.

A new simple method for measuring red cell aggregation.

A viscometric technique is outlined for the measurement of red cell aggregation (RCA). Samples are submitted to a constant shear rate of 2,4 s-1. The resulting time dependent torque signal reaches a peak soon after starting the rotation and falls within seconds to a constant baseline, thereby describing an area "F" with the baseline. The shear history of the sample being strictly controlled, "F" is reproducible and shows a direct, positive correlation with RCA as determined for instance in the "aggregometer".

Intracellular electrolyte concentrations in the frog skin epithelium: effect of vasopressin and dependence on the Na concentration in the bathing media.

The intracellular electrolyte concentrations of the frog skin epithelium have been determined in thin freeze-dried cryosections using the technique of electron microprobe analysis. Stimulation of the transepithelial Na transport by arginine vasopressin (AVP) resulted in a marked increase in the Na concentration and a reciprocal drop in the K concentration in all epithelial cell layers. The effects of AVP were cancelled by addition of amiloride. It is concluded from these results that the primary mechanism by which AVP stimulates transepithelial Na transport is an increase in the Na permeability of the apical membrane. However, also some evidence has been obtained for an additional stimulatory effect of AVP on the Na pump. In mitochondria-rich cells and in gland cells no significant concentration changes were detected, supporting the view that these cells do not share in transepithelial Na transport. Furthermore, the dependence of the intracellular electrolyte concentrations upon the Na concentration in the outer and inner bathing solution was evaluated. Both in control and AVP-stimulated skins the intracellular Na concentration showed saturation already at low external Na concentrations, indicating that the self-inhibition of transepithelial Na transport is due to a reduction of the permeability of the apical membrane. After lowering the Na concentration in the internal bath frequently a Na increase in the outermost and a drop in the deeper epithelial layers was observed. It is concluded that partial uncoupling of the transport syncytium occurs, which may explain the inhibition of the transepithelial Na transport and blunting of the AVP response under this condition.

[A comparative study of the reflective and apperceptive refractions (author's transl)]. / Reflektorische und apperzeptive Refraktionsbestimmung. Eine vergleichende Studie zwischen manueller bzw, automatischer Refraktometermessung und subjektiver Refraktionsbestimmung.

Reflective (objective) refraction differs basically from apperceptive (subjective) refraction in that it excludes conscious seeing from the measuring procedure. As a result limits can be established for the subjective acceptability of refraction values with automatic or manual refractometers. In a comparative study of 50 cases the correction values obtained with the manual refractometer PR 50 (Rodenstock) and the automatic refractometers Dioptron (Coherent Radiation) and Auto-refractor 6600 (Acuity Systems) were compared with the results of conventional subjective refraction. Criterion for this comparison was the visual acuity achieved with the correction values. In 55% of the cases the same, in some cases even better visual acuity was achieved than with subjective refraction. In the other 45% a direct comparison of the reflective and the subjective refraction values shows which component (sphere, cylinder) of the refractometer correction value leads to a lower visual acuity.

Intracellular electrolyte concentrations in epithelial tissue during various functional states.

The scanning electron microscope together with an energy dispersive system was used to quantify intracellular elemental concentrations of transporting epithelial cells under a variety of experimental conditions. In the frog skin, the Na transport pool is comprised of the intracellular compartments of all vital cells in the different cell layers, except the mitochondria rich cells. The Na content of this transport pool exchanges easily with the epithelial (outer) bathing solution. Vasopressin increases the Na permeability of the corial cell barrier. Proximal and distal tubular cells of the rat kidney show differences in the pattern of intracellular element concentrations. The distal tubular cell is more resistant to 20 min of ischemia than the proximal cell. The changes in intracellular electrolyte concentrations following 60 min of ischemia are reversible after reperfusing the kidney with blood for 60 min. In the cells of the frog skin and rat kidney, Na and K were equally distributed between the cytoplasm and the nucleus. Differences exist for P, Cl and dry weight.