Lipid and fatty acid composition of cytoplasmic membranes from Streptomyces hygroscopicus and its stable protoplast-type L form.

The cells of an L-form strain of Streptomyces hygroscopicus have been grown for 20 years without a cell wall. Their cytoplasmic membranes have high stability and an unusual structural polymorphism. To clarify the importance of the lipid components for these membrane properties, a comparative analysis has been carried out with purified membranes of L-form cells, of parent vegetative hyphal cells (N-form cells), and of protoplasts derived from the latter. The phospholipid classes and fatty acids were determined by thin-layer chromatography (TLC), two-dimensional TLC, high-performance liquid chromatography, gas chromatography, and mass spectrometry. The qualitative compositions of cardiolipin (CL), lyso-cardiolipin (LCL), phosphatidylethanolamine (PE1 and PE2), lyso-phosphatidylethanolamine (LPE), phosphatidylinositolmannoside (PIM), phosphatidic acid (PA), dilyso-cardiolipin-phosphatidylinositol (DLCL-PI), and the 13 main fatty acids were the same in the three membrane types. However, significant quantitative differences were observed in the L-form membrane. They consist of a three- to fourfold-higher content of total, extractable lipids, 20% more phospholipids, an increased content of CL and PIM, and a reduced amount of the component DLCL-PI. Furthermore, the L-form membrane is characterized by a higher content of branched anteiso 15:0 and anteiso 17:0 fatty acids compared to that of the membranes of the walled vegetative cells. These fatty acids have lower melting points than their straight and iso-branched counterparts and make the membrane more fluid. The phospholipid composition of the protoplast membrane differs quantitatively from that of the N form and the L form. Whereas the phospholipid classes are mostly similar to that of the N form, the fatty acid pattern tends to be closer to that of the L-form membrane. The membranes of both the L-form cells and the protoplasts need to be more fluid because of their spherical cell shape and higher degree of curvature compared with N-form membranes.

Designing computer assisted instruction programs for diabetic patients: how can we make them really useful?

Despite the increasing potential of computers for educational use, experience shows that few Computer Assisted Instruction (CAI) programs for patient education have been accepted into routine use by health care providers. A CAI program on hypoglycemia for insulin dependent diabetics, which was developed by the authors and has been widely used in Europe for over 6 years, is described and is used to illustrate some specific difficulties and possible solutions when using computers for patient education. We hope to show that patients suffering from a chronic disease, such as diabetes, require specific skills which are very different in nature from the theoretic knowledge they usually receive from different sources, including health care providers. In order to be really useful, a CAI program for patients must help them to cope with their disease and take into account patients' concerns, fears, and misconceptions as far as possible. Far beyond a detailed knowledge of the domain, a deep experience in patient education is mandatory to understand patients' needs.