Postnatal neurogenesis in the kitten retina

Postnatal neurogenesis in the kitten retina was studied using 3 H-thymidine radioautography. Kittens were injected with 3 H-thymidine at 1 day, 10 days, 3 weeks or 4 weeks after birth and allowed to survive until 14 weeks of age. Labeled neuronal nuclei were not found in the ganglion cell layer in any of the retinas, but they were seen in the other nuclear layers of the same retinas. In retinas from kittens injected at one day after birth, the peripheral 80% of the length of the retina (in sections cut parallel to the dorsoventral meridian) contained labeled nuclei; the central 20%, around the optic disc, contained no labeled nuclei. Near the ora serrata most nuclei in both inner and outer nuclear layers were labeled. Away from the ora serrata the proportion of labeled to unlabeled nuclei gradually decreased. Labeled nuclei extended farther centrally in the inner than the outer nuclear layer. The same pattern of labeling was repeated in retinas from kittens injected at ten days after birth, but fewer nuclei were labeled, and the central, unlabeled region around the optic disc was longer–55% of the length of the retina. Only a few nuclei near the ora serrata were labeled in retinas from kittens injected at three weeks after birth, and no labeled neurons were found in kittens injected at four weeks. From these results we conclude that all of the ganglion cells in the kitten retina are present by one day after birth, as are all of the other neurons in the central retina. In peripheral regions of the inner and outer nuclear layers, proliferation of cells destined to become neurons continues up to three weeks after birth.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50008/1/901870306_ftp.pd

Retinofugal pathways in the longnose gar Lepisosteus osseus (linnaeus)

Retinal projections were studied with autoradiographic and silver methods in the gar, Lepisosteus osseus , one of the two surviving members of the holostean actinopterygians. Contralaterally, the retina projects to the preoptic nucleus of the hypothalamus, and, via the medial optic tract, to the dorsal thalamus, medial ventral thalamic nucleus, nucleus pretectalis profundus pars ventralis and pars dorsalis, and the medial portion of the deep layer of the central zone in the optic tectum. The dorsal optic tract projects to the lateral ventral thalamic nucleus, nucleus pretectalis centralis, and the superficial white and gray zone of the optic tectum. The ventral optic tract terminates in the nucleus of the ventral optic tract, the lateral and medial ventral thalamic nuclei, nucleus pretectalis superficialis, nucleus pretectalis centralis, nucleus pretectalis profundus pars ventralis, the basal optic nucleus, and the superficial white and gray zone of the optic tectum. Ipsilateral projections are to similar sites, except for an absence of inputs to the lateral ventral thalamic nucleus from the dorsal tract and to the nucleus pretectalis superficialis, nucleus pretectalis profundus pars ventralis, and the basal optic nucleus from the ventral tract. The presence of ipsilateral retinal projections in gars is compared to their presumed absence in teleosts, and comparisons of retino-recipient targets in gars are made with teleosts and with non-actinopterygian vertebrates.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/49996/1/901660102_ftp.pd

Growth of the adult goldfish eye. III. Source of the new retinal cells

The manner in which new cells are added to the growing adult goldfish retina was examined using 3 H-thymidine radioutography. Cell proliferation leading to the formation of neurons is restricted to the retinal margin at the ora terminalis . New retina is added in concentric rings, with slightly more growth dorsonasally. The rate of cell addition is variable, averaging 12,000 cells/ day. These new cells account for about 20% of the total increase in retinal area; the remaining 80% is due to hypertrophy, or expansin, of the retina. In contrast to all of the other retinal cells, the rods do not appear to participate in the retinal expansion. This hypothesized immobility of the rods would create a shearing strain between the retinal layers resulting in a shift in their position relative to the other cells. Were they to maintain synaptic contacts with the same horizontal and bipolar cells, the rod axons would have to be elongated peripherally or the post-synaptic cell dendrites displaced centrally. Since neurons with this morphology have not been found in the goldfish retina, these observations suggest that the rods must be changing their synaptic connections as the retina grows.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50002/1/901760304_ftp.pd

Evaluation of [3H]proline for radioautographic tracing of axonal projections in the teleost visual system

The efficacy of [3H]proline radioautography for tracing retinal ganglion cell projections to the optic tectum of the jewel fish, Hemichromis bimaculatus, has been compared with that of degeneration techniques. There was good agreement between the various methods. Retinal projections to the optic tectum of two other teleosts, the oscar, Astronotus ocellatus, and the goldfish, Carrasius auratus, were examined radioautographically.In addition to conventional methods of analysis, radioautograms were scanned in a slit microdensitometer and by an automated isodensity scanning system. Results of studies with the protein synthesis inhibitor, cycloheximide, are compatible with the suggestion that axonally transported proteins labeled with [3H]proline may release diffusible precursors that are reincorporated into protein in adjacent regions.The possible advantages and limitations of radioautography of [3H]proline-labeled axonally transported protein in brief or extended studies are discussed in terms of the results obtained in the teleost visual system.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22035/1/0000453.pd

Sufficiency – does energy consumption become a moral issue?

Reducing the externalities from energy use is crucial for sustainability. There are basically four ways to reduce externalities from energy use: increasing technical efficiency (“energy input per unit energy service”), increasing economic efficiency (“internalising external costs”), using “clean” energy sources with few externalities, or sufficiency (“identifying ‘optimal’ energy service levels”). A combination of those strategies is most promising for sustainable energy systems. However, the debate on sustainable energy is dominated by efficiency and clean energy strategies, while sufficiency plays a minor role. Efficiency and clean energy face several problems, though. Thus,the current debate should be complemented with a critical discussion of sufficiency. In this paper, I develop a concept of sufficiency, which is adequate for liberal societies. I focus on ethical foundations for sufficiency, as the discussion of such is missing or cursory only in the existing literature. I first show that many examples of sufficiency can be understood as (economic) efficiency, but that the two concepts do not coincide. I then show that sufficiency based on moralization of actions can be understood as implementation of the boundary conditions for social justice that come with notions of liberal societies, in particular the duty not to harm other people. By this, to increase sufficiency becomes a duty beyond individual taste. I further illustrate this in the context of the adverse effects of climate change as externalities from energy use

Quantitative Beschreibung von Koaleszenzvorgängen in Extraktionskolonnen

A significant aspect of designing an extraction apparatus is determining the coalescence behavior of a given material system. As coalescence is strongly influenced by traces of impurities, tests have to be carried out with the same system, which is used for the later extraction process. Different measurement methods for determining the coalescence behavior of a system are described in the literature. The coalescence behavior for designing mixer-settler processes can be quantified in simple discontinuous lab-scale settling tests. At the same time, quantifying coalescence of a system in an extraction column is tedious as pilot-plant experiments have to be performed. Therefore, it was the objective of this work to develop a method to characterize the coalescence behavior in extraction columns with minimal effort. For this purpose, different measurement techniques discussed in the literature for quantifying coalescence were applied and compared. It was shown that the discontinuous settling test, which can be performed with comparatively low effort, can also be applied for characterizing coalescence in extraction columns. For transferring the results of the settling tests to extraction columns, model approaches, which are given in the literature, were improved. By applying these models, the coalescence behavior in extraction columns is separated into two factors: On the one hand, hydrodynamic effects determining e.g. frequency of drop collisions and collision intensity have to be modeled. The hydrodynamic effects depend on the geometry of a specific column and on the operating conditions and have to be characterized only once for each column type. On the other hand, coalescence behavior of a specific material system has to be quantified. The influence of the material system on the coalescence is characterized by the settling experiments. Thus, this new approach allows a universal characterization of coalescence for all common extraction equipment, namely mixer-settlers as well as columns, where the system specific coalescence is characterized in a simple and fast lab-scale experiment