Double-Helix Microscopy for Wide-Field 3-D Single-Molecule Fluorescence Imaging

We present methods to improve the localization accuracy in wide-field 3-D single-molecule double-helix microscopy. We analyze the optical efficiency of the system, the fundamental limit for 3-D localization, the estimation algorithms, and polarization sensitive detection

Neurotrophic factors in the testis

Neurotrophic factors, interacting with neurons to affect their growth, are a subset of the polypeptide growth factors. There is increasing evidence for a broader physiological role of these factors which includes effects on a variety of nonneuronal tissues. Among the cell systems, where neurotrophic factors have been hypothesized to exert local nonneurotrophic activities, the testis is of particular interest. This organ represents a complex biological unit which requires the concerted action of very diverse cell types interacting with each other in order to ensure correct spermatogenesis. As signaling molecules that may be involved in these intercellular communication events, various neurotrophic factors have attained considerable scientific attention. This article intends to summarize the presently available data on the distribution and possible local activities of neurotrophic factors and their receptors in testicular cells and provides further information on local expression sites of some of these factors in the human testis.Biomedical Reviews 1999; 10: 25-30

Panta rhei oder der mentale Fluss von Tatsachen: zur Reliabilität retrospektiv erhobener biographischer Ereignisse

'Die meisten empirischen Untersuchungen zur Transformation der DDR-Gesellschaft und deren Folgen für verschiedene Bevölkerungsgruppen basieren auf einem retrospektiven Forschungsdesign. Die so erhobenen biographischen Ereignisse aus den Jahren vor der Wende werden als relativ zuverlässig angesehen. Anhand zweier Variablen aus dem Längsschnittdatensatz der Studenten Intervallstudie Leistung (SIL A-E, 1982-1992) wird aufgezeigt, dass auf die Rehabilität solcher Angaben nicht selbstverständlich vertraut werden darf. Re-Interpretationen werden von den Befragten auch für einmalige, abgeschlossene biographische Tatbestände vorgenommen. Die Art der Veränderung in der Darstellung ein und desselben Ereignisses hängt überzufällig vom nachfolgenden Lebensverlauf ab. Systemübergreifend angelegte Panelstudien sind von einmaligem Wert für Fragen sowohl der Transformationssoziologie als auch der Grundlagenforschung. Sie sollten stärker beachtet und weiterhin gefördert werden.' (Autorenreferat)'Most of the empirical studies about the transformation of the former East Germany and its consequences to different social groups are based an a retrospective research design. Biographical data surveyed that way are usually considered reliable. By using two variables from the longitudinal study 'Studenten-Intervallstudie Leistung' (SIL A-E, 1982-1992) it is shown that one cannot trust in the reliability of such Information. Reinterpretations are done for nonrecurring, completed biographical incidents, too. The way of describing the same incident significantly depends on the further course of life. Panel studies of different social systems are of unique importance for questions of socilogy of transformation as well as for basis research. They should be paid more attention to and promoted in the future.' (author's abstract)

The C-type natriuretic peptide system in the testis: a physiological role of neuroactive factors in Leydig cells

Androgen production is the primary function of testicular Leydig cells. Recently, Leydig cells of the human testis have been shown to possess, along with well developed smooth endoplasmic reticulum, cytoplasmic vesicles and storage granules similar to those found in neuroendocrine and nerve cells. Moreover, a series of nerve cell-specific substances has been detected in Leydig cells. However, little is known about the physiological role of these molecules in testicular function.Biomedical Reviews 1997; 8: 111-117

Dual nature of Leydig cells of the human testis

This review is devoted to the human Leydig cell, and systematizes published and own unpublished results from studies performed during the last decade. Leydig cells are the main cell type in the testis that produce androgens which are important for the development of the male genital organs, secondary sex characteristics and behavior as well as for the processing and maintenance of spermatogenesis. A lot of information accumulated provides evidence that Leydig cells of the human testis and the testis of some other species express or possess immunoreactivities for numerous marker substances characteristic for nerve and neuroendocrine cells. It is shown that human Leydig cells, beside of markers for steroidogenic activity, possess: neuronal markers, synaptic and storage vesicle proteins, neural cytoskeletal proteins, 5-hydroxytryptamine, enzymes involved in the synthesis of catecholamines, neurohormones and/or their receptors, neuropeptides, calcium-binding proteins, cell adhesion molecules, glial cell antigens, components of the nitric oxide/cyclic guanosine monophosphate system, components of the renin/angiotensin system, and numerous growth factors and their receptors. These results provide new evidence for the neuroendocrine nature of Leydig cells. As consequence, two main questions arise: (i) the origin of Leydig cells and (ii) their functional significance as neuroendocrine cells. The presumption that Leydig cells originate from mesenchymal-like cells of the mesonephros is the most common view in the literature. However, no data are provided concerning the origin of the stem cells from which the Leydig cell lineage develops. Mesenchyme comprises the embryonic connective tissue cells that may have mesodermal, ectodermal and neuroectodermal (neural crest) origin. In this relation and based on the recently established neuroendocrine feature, we speculate that Leydig stem cells may detach from unknown regions of the neural crest and migrate to the mesonephric and gonadal anlage at early stages of development. The functional significance of Leydig cells as neuroendocrine cells is also illustrated on the basis of the nitric oxide/cyclic guanosine monophosphate system. Accordingly, Leydig cells may regulate their steroidogenic activity by an intracrine or autocrine fashion. Furthermore, they are probably able to synchronize the activity of the cells in a Leydig cell cluster by a paracrine way. Leydig cells may influence the contractile activity of the smooth muscle cells of blood vessels, thus regulating the blood flow rate and the permeability for hormones and nutritive substances. Also, Leydig cells may regulate the contractile state of peritubular myofibroblasts and myofibroblasts and smooth muscle cells of the tunica albuginea. Similarly, Leydig cells may communicate with Sertoli cells and germ cells of the seminiferous tubules. Leydig cells are a relatively stable, heterogeneous population of cells in the human testis which persists even in cases of impaired spermatogenesis, fibrosis and different pathological changes of the testis. This fact suggests that Leydig cells survive under unusual conditions due to precise regulatory systems which make them to a larger extent independent from the local homeostasis.Biomedical Reviews 1996; 6: 11-41

Bestimmungen des Hämoglobingehaltes im Blut der zu- und abführenden Gefässe der Leber und der Milz : Inaugural-Dissertation zur Erlangung des Grades eines Doctors der Medicin

http://tartu.ester.ee/record=b2017251~S1*es