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At least 829 records · Page 46Linked to original sources
PubMed1999

A chemically labeled cytotoxic agent: two-photon fluorophore for optical tracking of cellular pathway in chemotherapy.

Chemotherapy is commonly used in the treatment of cancers. However, the mechanism of action of many of these agents is not well understood. We present the synthesis of a two-photon fluorophore (C625) and its biological application when chemically linked to a chemotherapeutic agent (AN-152). By using two-photon laser-scanning microscopy, the drug:fluorophore conjugate can be observed directly as it interacts with receptor-positive cell lines. The results of this project visually show the receptor-mediated entry of AN-152 into the cell cytoplasm and subsequently into the nucleus. These observations will allow for better understanding of the drug's therapeutic mechanism, which is a subject of ongoing research aimed at improving present methods for cancer therapy.

Antineoplastic Agents↗
PubMed1989

Pre-existing neuronal pathways in the developing optic lobes of Drosophila.

We have identified a set of larval neurones in the developing adult optic lobes of Drosophila by selectively labelling cells that have undergone only a few mitoses. A cluster of three cells is located in each of the optic lobes near the insertion site of the optic stalk. Their axons fasciculate with fibres of the larval optic nerve, the Bolwig's nerve, and then form part of the posterior optic tract. These cells are likely to be first order interneurones of the larval visual system. Unlike the Bolwig's nerve, they persist into the adult stage. The possibility of a pioneering function of the larval visual system during formation of the adult optic lobe neuropil is discussed.

Animals↗
PubMed1985

[Brain of the cod (Gadus morhua morhua, Linné 1758) (Pisces, Paracanthopterygii). Qualitative and quantitative analysis of major subdivisions].

The Cod, Gadus morhua, is a North Atlantic fish of the family Gadidae which occurs at depths of 80 to 600 m (usually 150 to 200 m). It often occurs in shoals and tends to be migratory. It has a typical teleost brain except for the gadid feature of long olfactory tracts. Gadid fishes have a low level of encephalization (RIDET, 1982). The index of encephalization of the Cod is near the mean for the family. This index changes with season due to the change in body weight; it is lowest during the spawning season (which takes place in spring). Five subspecies of Gadus morhua are recognized. A comparison was made of the index of encephalization of the subspecies which is restricted to the White Sea, Gadus morhua maris albi, Derjugin 1920 and Gadus m. morhua, Linné 1758. The index of the White Sea form was significantly higher, thus supporting its recognition as subspecies. A volumetric analysis was made of the subdivisions of the Cod brain. It was found to have a large cerebellum, large medulla oblongata and a tendency to macrosmy, but a small telencephalon and tectum opticum (tendency to micropty). This is what would be expected from the environment and habits of this fish.

Animals↗
PubMed1980

Aberrant retinotectal pathways induced by larval unilateral optic nerve section in Xenopus.

Following unilateral optic nerve section in Xenopus tadpoles and toadlets, the reformation of visual pathways and retinotectal projections was analyzed using [3H]proline autoradiography. Bilateral retinotectal projections were found in 61% of the animals operated on between stages 42 and 58. In these animals, the projections were established through multiple aberrant pathways which included the oculomotor nerve, the trigeminal nerve and the posterior commissure. In contrast, in animals with optic nerve section at stage 62 or after metamorphosis, the regenerated optic fibres arrived at the contralateral and ipsilateral tecta through normal visual pathways.

Animals↗
PubMed1999

Microcirculatory oxygenation and shunting in sepsis and shock.

OBJECTIVE: To review optical spectroscopic techniques for assessment of the determinants of tissue oxygenation and to evaluate the notion that the disturbances in oxygen pathways in sepsis can be accounted for by enhanced functional shunting of parts of the microcirculation. DATA RESOURCES: Experimental data from previous research and the literature were analyzed. STUDY SELECTION: The data selected pertained to a) whether cellular distress in sepsis is caused by tissue hypoxia or disturbed metabolic pathways, b) optical spectroscopic techniques used to study microcirculatory oxygenation, and c) possible mechanisms underlying shunting of the microcirculation in hypoxemia and sepsis. STUDY SYNTHESIS: Despite resuscitation of oxygen-derived variables, signs of regional tissue hypoxia persist in sepsis. The mechanisms underlying this condition are expected to be associated with oxygen pathways in the microcirculation. Optical spectroscopic techniques are providing new insights into these mechanisms. These include absorption spectroscopy for hemoglobin saturation of erythrocytes, reduced nicotinamide adenine dinucleotide fluorescence for tissue mitochondrial bioenergetics, and palladium-porphyrin phosphorescence for microvascular PO2. Reduced nicotinamide adenine dinucleotide videofluorescence studies have shown the heterogeneous nature of hypoxia. Measurement of gut microvascular PO2 in pigs has shown the development of a PO2 gap between microvascular PO2 and venous PO2 during hemorrhage and endotoxemia, with a larger gap occurring in sepsis than in hemorrhage. It is hypothesized that this difference is caused by the enhanced shunting of the microcirculation present in sepsis. CONCLUSIONS: Microcirculatory distress may form one of the earliest stages in the progress of sepsis to multiple organ failure, and shunting of the microcirculation may be an important contributing factor to this development. To evaluate the severity of microcirculatory distress and the effectiveness of resuscitation strategies, new clinical technologies aimed at the microcirculation will need to be developed. It is anticipated that optical spectroscopy will play a major role in the development of such tools.

Humans↗
PubMed2005

Imaging the secretory pathway: the past and future impact of live cell optical techniques.

Classically, the secretory pathway has been studied using a combination of electron microscopic, biochemical and genetic approaches. In the last 20 years with the arrival of molecular biology and epitope tagging, fluorescence microscopy has become more important than previously. Moreover, with the common availability of Green Fluorescent Protein (GFP) and confocal microscopes in the last 10 years, live cell imaging has become a major experimental approach. This review highlights the impact of the recent introduction of single-cell quantitative time-lapse imaging and photobleach techniques on the study of the secretory pathway, and the potential impact of those optical techniques which may play a significant future role in the study of the Golgi apparatus and the secretory pathway. Particular attention is paid to techniques (Fluorescence Resonance Energy Transfer, Fluorescence Correlation Spectroscopy) which can monitor protein-protein interactions in living cells.

Animals↗
PubMed1991

Gliosis during optic fiber regeneration in the goldfish: an immunohistochemical study.

Antisera directed against the 48 kDa and 50 kDa cytoskeletal antigens were used to examine changes in the astroglial fabric of the goldfish visual pathways following optic nerve crush. Several major observations are described. First, an optic nerve crush lesion in these animals appears to be devoid of glial cells for at least the first month after surgery. As a corollary, regenerating axons that grow across the lesion may do so over an aglial substrate. Once the axons cross the lesion, their growth is confined to the astroglial domains of the proximal nerve stump. In the optic nerve, gliosis comprises hypertrophy of astrocytic processes such that the open framework characterizing the normal nerve is obscured. In addition, during regeneration, optic nerve glia express large amounts of the 50 kDa cytoskeletal protein, which they ordinarily express at only minimal levels. In the optic tract, gliosis is reflected in a markedly increased expression of the 50 kDa protein as well as an apparent increase in the number and complexity of glial processes. In addition, optic tract glia begin to express the 48 kDa antigen during regeneration. This protein is ordinarily confined for the most part to the optic nerve and is not seen in the tract glia. Finally, no obvious changes were seen in the glia of the optic tectum. These results demonstrate many points of similarity between gliosis in the goldfish and in mammals. However, in some particulars the two responses differ, and it is possible that these differences are related to the differing ability of central axons to regenerate in the two groups of organisms.

Animals↗
PubMed1989

Centrifugal pathways to the retina: influence of the optic tectum.

Two types of centrifugal pathways to the retina have been found in the vertebrates, according to the location of the cell bodies and presence or absence of connections with the optic tectum. One type is represented by the isthmo-optic nucleus (ION) of birds and, therefore, termed "ION-type" retinopetal system. The other type is termed "non-ION-type" retinopetal system. The ION-type retinopetal systems have been found in the cyclostomes, teleosts, reptiles, and birds. This review describes the anatomy and physiology of the ION-type retinopetal systems, mainly of birds and teleosts. On the basis of anatomical and physiological evidence cited in this review, the ION-type retinopetal systems can be regarded as the tectofugal pathways to the retina. The function of the ION-type retinopetal systems is discussed in detail, with special emphasis on their relation to the role of the tectum in mediating visuomotor behavior.

Animals↗
PubMed1992

Distinctive pattern of organisation in the retinofugal pathway of a marsupial: II. Optic chiasm.

In the mammalian optic chiasm retinal axons from each eye divide into two populations, those that decussate and those that remain uncrossed. In eutherian (placental) mammals, the separation of these pathways is not reflected in the structure of the chiasm. The two populations from each eye are mixed through each hemichiasm, segregating only at the midline, where the uncrossed projection turns back. In this study the optic chiasm of a marsupial, the wallaby, Setonix brachyurus (quokka) has been investigated with staining and neuronal tracing techniques. The chiasm of this mammal is quite different from that of eutherian mammals. In coronal section it can be morphologically subdivided into three regions, a central body in which fasciculated groups of axons from each eye interdigitate across the midline, and two distinct lateral regions, one on each side, which contain the uncrossed retinal projections. In the rostral chiasm the lateral regions are separated from the main body of the chiasm by vertically oriented fibre-free regions. Caudally, the lateral regions increase in size and become less distinct as increasing numbers of contralaterally projecting axons that have crossed the midline project into them. However, the two populations remain predominantly segregated in this region. As the lateral regions develop, the central body of the chiasm becomes thinner and finally detaches at the midline to form the two optic tracts. The routes taken by retinal axons through the eutherian and marsupial chiasm appear to be fundamentally different. Therefore, the developmental factors that determine the laterality of retinal projections are likely to show significant differences in the two mammalian groups.

Animals↗