Search

Acidic microenvironmental conditions combined with large hypoxic areas are ubiquitous hallmarks of most solid tumors. They result from a poorly organized vascularization and a deviant energy metabolism. There is convincing evidence supporting the hypothesis that such physico-chemical conditions promote the microevolution of malignant cells, inhibit the cellular immune response, and favor tumor cell invasion. In agreement with published data, our cell biological analyses and computer simulations indicate that treatment schemes which restore a tumor microenvironment reflecting that one found in normal tissues might improve the efficiency of immunotherapies and classical methods for cancer treatment. We suggest that the tumor microenvironment could be effectively monitored and manipulated by means of silicon-based feedback bioactuators which are controlled by integrated microsensors. In principle, miniaturized bioactuators can be implanted directly at the sites of inoperable tumors and metastases where they function as a "pH clamp" and thereby can reconstitute normal physicochemical conditions. Drug application could be precisely controlled by an integrated microprocessor. Our paper summarizes the current state of development of microsensor-based feedback bioactuators and outlines possible applications in biophysical cancer treatment.

Even with intensive insulin therapy it is impossible to reach physiological blood glucose levels in insulin-dependent diabetes mellitus. Because of the high costs and technical problems involved in islet cell transplantation broad applicability of this therapy seems uncertain. An alternative approach is the development of molecular-engineered insulin-producing clonal cell lines. The main interest is in rodent insulinoma cell lines and neuroendocrine AtT-20ins cells. This paper reviews the current knowledge about glucose-stimulated insulin secretion and the problems that have to be solved before these cells can be used for therapy in diabetes mellitus.

This part of the paper deals with the neurophysiological background of speech analysis and hearing of music. Single vowel- and consonant-detector cells could be clearly separated at the colliculus and geniculate level (Kallert, Keidel). Musical stimulation is decoded at three levels: hair cells, geniculate, and auditory cortex. Human cortical evoked potentials represent rhythm, consonance, and (as DC-shift) the emotional content of music. Marked harmonics, even of single hair-cell vibrations and in single units of medial geniculate in combination with clock-cell networks, are the physiological basis of "harmony" in music. Dissonant stimuli are detectable at the cortical level in man (Finkenzeller, Keidel).

In this paper a systematic approach to the mathematical modeling of intracellular Ca2+ oscillations is introduced. After a structured analysis a stochastic model of the system is derived which is numerically tractable by means of a stochastic simulation. A critical discussion of theoretical models for Ca2+ oscillations reveals that not all of the proposed mechanisms are consistent with experimental data. In addition, a model for oscillatory calcium waves is presented. Uncovering these mechanisms facilitates the design of anti-mitotic drugs interfering with Ca2+ metabolism.

The paper gives a short review of biochemical and genetic analyses of the eukaryotic cell cycle and cell division. Emphasis is placed on the interrelationship of macromolecular syntheses during chromosome replication, the possible involvement of protein phosphorylation in chromosome condensation, the function of contractile proteins in mitosis and cytokinesis and on mechanisms which trigger cell proliferation.

The discussion on the possible increase of solar UV on earth due to the destruction of the stratospheric ozone has led to a renewed interest in the action of ultraviolet radiation on biological systems. The paper deals with changes at the cellular level stressing particularly molecular alterations in deoxyribonucleic acid, the carrier of genetic information. The most important repair processes by which lesions are removed or bypassed are described. It is also discussed whether the effectivity of a complex spectrum can be predicted on the basis of measurements with monochromatic radiation. Furthermore, possible consequences on human health are outlined which may be derived from cellular studies.

Nucleic acid hybridization techniques (e.g., Southern blotting and in situ hybridization) gain increasing importance in laboratory medicine, as demonstrated by examples in this paper. The molecular basis of this approach to detect nucleic acids homologous to known DNA probes is explained. It is concluded that this technique has advantages in the detection of pathogens compared to other methods used in laboratory medicine.

This paper is an introduction to the problems of dumping at sea of radioactive wastes. A short survey is given on the dumping actions previously performed, the legal justification by international treaties, and the most important radioecological questions.

This paper deals with the important trace-materials in the natural and anthropogenetic influenced atmosphere. They exist as gases as well as solid and solid-fluid particles. They are significant for numerous physical processes in the atmosphere and have also a direct influence on our biological environment.

"Osteosynthesis" or internal fixation is the term used for operative reduction of bone fragments. The aim of the procedure is to effect such stable fixation that the affected extremity may be moved freely. The paper gives a survey of the technical basis of and indications for modern methods of internal fixation.