[Real change or natural fluctuation?] / Echte verandering of natuurlijke schommeling?

When monitoring patients over time, it may be difficult to distinguish 'real changes' from so-called 'natural fluctuations' when interpreting consecutive laboratory results. Consider a patient whose cholesterol level has decreased from a baseline 6.6 mmol/L to 6.1 mmol/L six months after receiving lifestyle advice. How likely is it that this is a 'real change', reflecting a lifestyle change, rather than random fluctuation? Physicians mostly rely on their intuition and clinical experience when interpreting changes in consecutive laboratory results. For inexperienced physicians, the lack of an easy reference for the interpretation of consecutive laboratory results can make decision-making challenging. We have developed the medical/educational smartphone app Labtracker+ that calculates the probability of a 'real change' between two consecutive laboratory results, using biological variation data from scientific literature and analytical precision that is achieved in contemporary laboratories. This approach may complement intuitive, experience-based interpretations of consecutive laboratory results.

Lens differentiation. Crystallin synthesis in isolated epithelia from calf lenses.

In the calf eye lens, four morphologically distinct cell types can be detected: three in the epithelial monolayer and one in the cortical part. During differentiation, there is a quantitative change in the synthesis of crystallin subunits. A marked increase in alphaA-chains and several beta-crystallin polypeptides accompanies the transition from epithelial to fiberlike lens cells while synthesis of the non-crystallin proteins diminishes significantly.

Dedifferentiation of lens epithelial cells in tissue culture.

Lens epithelial cells can be kept in their original differentiated state or brought to dedifferentiation depending on the culture conditions. The different stages of differentiation can be identified using specific markers, namely the activity of steroid metabolizing enzymes, and the synthesis of specific structural lens polypeptides. For this reason lens epithelial cells in tissue culture provide a unique system for the study of the regulation of RNA and protein biosynthesis.

Isolation and translation of non-crystallin messenger RNA from calf lens.

Affinith chromatography of lens polyribosomal RNA on oligo(dT)-cellulose yields three fractions. As arule the second fraction has been neglected in other studies reported in the literature. According to our investigations this fraction in particular contains the messengers for the non-crystallin lens proteins.

Further studies on the lens cell-free system. In vitro synthesis of the non-crystallin lens proteins.

1. The lens cell-free system synthesizes in addition to the crystallins, polypeptides which co-electrophorese with lens plasma membrane protein components. 2. Isolated lens polysomes can be translated in a heterologous cell-free system. They code for both the crystallins and membrane-protein-like components. 3. If messengers isolated from these polysomes by affinity chromatography on oligo-(dT)-cellulose are added to a heterologous cell-free system, only lens proteins of lower molecular weight are synthesized. 4. Different ionic conditions are required for optimal translation of different lens messengers.