Tritiated uridine uptake in the retinal ganglion cell layer of the cat during normal development and after visual cortex ablation

The short-term metabolic response of immature retinal ganglion cells to destruction of their target cells in the dorsal lateral geniculate nucleus (dLGN) was assessed in newborn cats. Retrograde degeneration of virtually all dLGN cells was induced by ablation of the 13 contiguous areas of visual cortex on the day of birth. The metabolic response of retinal ganglion cells to this loss of target cells in dLGN was determined by exposing the ganglion cell layer to tritiated uridine, a precursor of RNA. Control measurements were made from unoperated littermates. Following sectioning and processing of the retinae from both groups of kittens for autoradiography, silver grain densities overlying the cellular profiles in the ganglion cell layer were calculated. These calculations revealed levels of uridine incorporation at Postnatal Day 4 in both groups of kittens significantly higher than at either Postnatal Day 2 or 7, but no significant differences between the two groups on any day examined. These results show that the level of RNA synthesis in retinal ganglion cells increases temporarily during the first postnatal week and that this synthesis is unaffected by the death of target cells in the dLGN. The temporary increase may be related to the establishment of synaptic connections on retinal ganglion cells by their afferent bipolar and amacrine neurons in the inner nuclear layer.     

Electrochromic properties of nanocrystalline tungsten oxide thin films

Tungsten trioxide films formed of aggregates in the nanometric range have been deposited by thermal evaporation and condensation method. From the atomic force microscopy study, the aggregate dimensions were found to be in the range between 350 nm and 450 nm. The optical, structural and electrochromic performance of these films under lithium intercalation is studied in detail and their properties are compared to those of continuous films of tungsten trioxide. The films show a slightly elevated diffuse reflectance in the lower wavelength range and a very high transmission in the solar and visible wavelengths. Under lithium intercalation, the films exhibit a very good degree of electrochromic optical modulation in both these spectral ranges and hence, are very suitable for electrochromic device application. The high degree of change between the clear state and the colored state render such nanocrystalline films more efficient in their electrochromic performance than the conventional continuous films.     

Sperm trading by volume in a hermaphroditic flatworm with mutual penis intromission

When sperm donation is costly, insemination is reciprocal and ejaculate size is a good predictor of an individual's reproductive state, internally fertilizing hermaphrodites are expected to donate more sperm when they receive more, resulting in sperm trading by volume. We compared the amounts of sperm exchanged reciprocally between partners of the planarian flatworm Dugesia gonocephala. In the field, mating individuals had more self sperm, but were less allosperm depleted than nonmating individuals. Larger individuals also had more self sperm and transferred more sperm. Although individuals mated assortatively by size, self sperm reserves were not correlated within pairs. Nevertheless, mating partners exchanged similar amounts of sperm, even after correcting for self sperm availability. Hence, individuals give more sperm not only when they have more, but also when they receive more. This is the first indication that sperm trading by volume occurs in a simultaneous hermaphrodite with mutual penis intromission. It appears to be achieved by both partners donating sperm until the partner with the lowest self sperm reserves finishes ejaculation and completes spermatophore transfer. In response, the other partner ends sperm donation as well, and transfers its spermatophore with only a short delay. The evolution of conditional sperm exchange in this species may be explained by the fact that male mating rate is limited owing to the time needed to replenish self sperm reserves. Copyright 1998 The Association for the Study of Animal Behaviour     

Getting into the Living Memory Box: Family archives & holistic design

Digital archives of personal memories are becoming increasingly technically feasible, but there remain significant interaction design challenges. In this paper, we present a research and design study of the Living Memory Box, a device and service to assist families in preserving memories in a variety of media forms. Through a series of ethnographic interviews, design activities and focus groups, we have developed recommendations for the design and development of future personal memory systems and appliances. These improvements must be considered by future researchers in the coordination of multiple disciplines toward successful holistic systems.     

Engraftment of unrelated donor stem cells in children with familial amegakaryocytic thrombocytopenia

Congenital amegakaryocytic thrombocytopenia is an extremely rare disorder for which bone marrow transplantation offers the only possibility for cure. The pathophysiology is unclear. Two children with familial amegakaryocytic thrombocytopenia underwent unrelated donor transplantation (bone marrow in one, umbilical cord blood in the second) after a preparative regimen of cyclophosphamide and total body irradiation. Both patients failed initial engraftment, required further donor stem cell infusions and are currently well with sustained engraftment, 16 months and 7 months after transplantation, respectively. The difficulty in achieving engraftment of unrelated donor stem cells in these children suggests that in future cases additional measures to achieve engraftment may be necessary, for example, a more aggressive preparative regimen or an increased stem cell dose.     

Enrichment of presenilin 1 peptides in neuronal large dense-core and somatodendritic clathrin-coated vesicles

Presenilin 1 is an integral membrane protein specifically cleaved to yield an N-terminal and a C-terminal fragment, both membrane-associated. More than 40 presenilin 1 mutations have been linked to early-onset familial Alzheimer disease, although the mechanism by which these mutations induce the Alzheimer disease neuropathology is not clear. Presenilin 1 is expressed predominantly in neurons, suggesting that the familial Alzheimer disease mutants may compromise or change the neuronal function (s) of the wild-type protein. To elucidate the function of this protein, we studied its expression in neuronal vesicular systems using as models the chromaffin granules of the neuroendocrine chromaffin cells and the major categories of brain neuronal vesicles, including the small clear-core synaptic vesicles, the large dense-core vesicles, and the somatodendritic and nerve terminal clathrin-coated vesicles. Both the N- and C-terminal presenilin 1 proteolytic fragments were greatly enriched in chromaffin granule and neuronal large dense-core vesicle membranes, indicating that these fragments are targeted to these vesicles and may regulate the large dense-core vesicle-mediated secretion of neuropeptides and neurotransmitters at synaptic sites. The presenilin 1 fragments were also enriched in the somatodendritic clathrin-coated vesicle membranes, suggesting that they are targeted to the somatodendritic membrane, where they may regulate constitutive secretion and endocytosis. In contrast, these fragments were not enriched in the small clear-core synaptic vesicle or in the nerve terminal clathrin-coated vesicle membranes. Taken together, our data indicate that presenilin 1 proteolytic fragments are targeted to specific populations of neuronal vesicles where they may regulate vesicular function. Although full-length presenilin 1 was present in crude homogenates, it was not detected in any of the vesicles studied, indicating that, unlike the presenilin fragments, full-length protein may not have a vesicular function.