Distributions of aspartate aminotransferase and malate dehydrogenase activities in rat retinal layers.

1985 ◽  
Vol 33 (7) ◽  
pp. 624-630 ◽  
Author(s):  
C D Ross ◽  
D A Godfrey
Keyword(s):  
Energy Metabolism ◽  
Correlation Coefficient ◽  
Malate Dehydrogenase ◽  
Aspartate Aminotransferase ◽  
Horizontal Cell ◽  
Plexiform Layer ◽  
The Other ◽  
Retinal Layers ◽  
Cell Processes ◽  
Malate Aspartate Shuttle

Aspartate aminotransferase (AAT), an enzyme interconverting glutamate and aspartate, has been suggested to be a marker for glutamatergic and/or aspartatergic neurons. However, AAT, glutamate, and aspartate are also involved in cellular metabolism, e.g., the malate-aspartate shuttle. To investigate the extent to which AAT might be involved in these several functions in retina, the distribution of AAT activity in rat retinal layers was compared to that of malate dehydrogenase (MDH), an enzyme of aerobic metabolism proposed to be physically complexed with AAT in the malate-aspartate shuttle mechanism. The distribution of AAT activity in retinal layers closely paralleled that of MDH (correlation coefficient AAT versus MDH = 0.93). AAT activity was proportionately higher than MDH in the photoreceptor inner segments, containing a high density of mitochondria, and in the outer plexiform layer (OPL), containing photoreceptor terminals and bipolar and horizontal cell processes. The amount of total AAT activity in the inner segments related to the mitochondrial isoenzyme is almost twice that in the other layers tested, including the OPL. The correlation between AAT and MDH activities is consistent with AAT involvement in retinal energy metabolism, although other functions, such as neurotransmission, are possible.

scholarly journals Distribution of activities of aspartate aminotransferase isoenzymes and malate dehydrogenase in guinea pig retinal layers.

1987 ◽  
Vol 35 (6) ◽  
pp. 669-674 ◽  
Author(s):  
C D Ross ◽  
D A Godfrey
Keyword(s):  
Guinea Pig ◽  
Malate Dehydrogenase ◽  
Aspartate Aminotransferase ◽  
Energy Production ◽  
Outer Nuclear Layer ◽  
Plexiform Layer ◽  
Inner Plexiform Layer ◽  
Retinal Layers ◽  
Metabolic Reactions ◽  
The Difference

Distributions of activity of the cytosolic (cAAT) and mitochondrial (mAAT) isoenzymes of aspartate aminotransferase and of malate dehydrogenase (MDH) were determined in guinea pig retinal layers. The distribution of total AAT activity (tAAT = cAAT + mAAT) and of mAAT activity correlated well (r = 0.88-0.91) with the distribution of MDH activity. mAAT activity was highest in the inner segments of the photoreceptors; there was a greater than twelve-fold difference between activity in that layer and in the inner retinal layers. cAAT activity was also highest in the inner segments, but the difference between the activity in the inner segments and the other layers was not nearly as great as with mAAT. cAAT activity was also relatively high in the outer nuclear layer, outer plexiform layer, and part of the inner plexiform layer. The high activity of cAAT, mAAT, and MDH in the inner segments indicates that all of these enzymes are involved in metabolic reactions related to energy production and/or to photoreceptive processes in the outer segments and, therefore, that the enzymes are probably involved in energy-related metabolism at synapses. However, other functions, including those related to neurotransmission, are not excluded.

Processing of S-cone signals in the inner plexiform layer of the mammalian retina

2013 ◽  
Vol 31 (2) ◽  
pp. 153-163 ◽  
Author(s):  
KIYOHARU J. MIYAGISHIMA ◽  
ULRIKE GRÜNERT ◽  
WEI LI
Keyword(s):  
Ganglion Cell ◽  
Short Wavelength ◽  
Plexiform Layer ◽  
The Other ◽  
Current Understanding ◽  
Inner Plexiform Layer ◽  
Color Information ◽  
Long Wavelength ◽  
Mammalian Retina ◽  
Cell Processes

AbstractColor information is encoded by two parallel pathways in the mammalian retina. One pathway compares signals from long- and middle-wavelength sensitive cones and generates red-green opponency. The other compares signals from short- and middle-/long-wavelength sensitive cones and generates blue-green (yellow) opponency. Whereas both pathways operate in trichromatic primates (including humans), the fundamental, phylogenetically ancient color mechanism shared among most mammals is blue-green opponency. In this review, we summarize the current understanding of how signals from short-wavelength sensitive cones are processed in the primate and nonprimate mammalian retina, with a focus on the inner plexiform layer where bipolar, amacrine, and ganglion cell processes interact to facilitate the generation of blue-green opponency.

scholarly journals Robust syntaxin-4 immunoreactivity in mammalian horizontal cell processes

2007 ◽  
Vol 24 (4) ◽  
pp. 489-502 ◽  
Author(s):  
ARLENE A. HIRANO ◽  
JOHANN HELMUT BRANDSTÄTTER ◽  
ALEJANDRO VILA ◽  
NICHOLAS C. BRECHA
Keyword(s):  
Horizontal Cell ◽  
Plexiform Layer ◽  
Horizontal Cells ◽  
Snare Proteins ◽  
Double Labeling ◽  
Subcellular Compartment ◽  
Feedback Communication ◽  
Syntaxin 4 ◽  
Molecular Machinery ◽  
Cell Processes

Horizontal cells mediate inhibitory feed-forward and feedback communication in the outer retina; however, mechanisms that underlie transmitter release from mammalian horizontal cells are poorly understood. Toward determining whether the molecular machinery for exocytosis is present in horizontal cells, we investigated the localization of syntaxin-4, a SNARE protein involved in targeting vesicles to the plasma membrane, in mouse, rat, and rabbit retinae using immunocytochemistry. We report robust expression of syntaxin-4 in the outer plexiform layer of all three species. Syntaxin-4 occurred in processes and tips of horizontal cells, with regularly spaced, thicker sandwich-like structures along the processes. Double labeling with syntaxin-4 and calbindin antibodies, a horizontal cell marker, demonstrated syntaxin-4 localization to horizontal cell processes; whereas, double labeling with PKC antibodies, a rod bipolar cell (RBC) marker, showed a lack of co-localization, with syntaxin-4 immunolabeling occurring just distal to RBC dendritic tips. Syntaxin-4 immunolabeling occurred within VGLUT-1-immunoreactive photoreceptor terminals and underneath synaptic ribbons, labeled by CtBP2/RIBEYE antibodies, consistent with localization in invaginating horizontal cell tips at photoreceptor triad synapses. Vertical sections of retina immunostained for syntaxin-4 and peanut agglutinin (PNA) established that the prominent patches of syntaxin-4 immunoreactivity were adjacent to the base of cone pedicles. Horizontal sections through the OPL indicate a one-to-one co-localization of syntaxin-4 densities at likely all cone pedicles, with syntaxin-4 immunoreactivity interdigitating with PNA labeling. Pre-embedding immuno-electron microscopy confirmed the subcellular localization of syntaxin-4 labeling to lateral elements at both rod and cone triad synapses. Finally, co-localization with SNAP-25, a possible binding partner of syntaxin-4, indicated co-expression of these SNARE proteins in the same subcellular compartment of the horizontal cell. Taken together, the strong expression of these two SNARE proteins in the processes and endings of horizontal cells at rod and cone terminals suggests that horizontal cell axons and dendrites are likely sites of exocytotic activity.

Retinal structure in Latimeria chalumnae

1973 ◽  
Vol 266 (881) ◽  
pp. 493-518 ◽  
Keyword(s):  
Cell Layer ◽  
Horizontal Cell ◽  
Plexiform Layer ◽  
The Other ◽  
Inner Plexiform Layer ◽  
Latimeria Chalumnae ◽  
Oil Droplet ◽  
Myelinated Fibres

The retina of Latimeria chalumnae contains four types of visual cells; most are rods, and there are three types of cones. Rod outer segments are cylindrical and appearances at their bases suggest that they may be renewed discontinuously from the inner segment. The rods have simple synaptic spherules, each bearing a single basal filament ending in a club-shaped expansion. Type 1 cones contain an oil droplet, and have a complex synaptic pedicle bearing about 12 basal filaments. Type 2 cones have no droplet, and a pedicle bearing about six basal filaments and of complexity between that of rods and type 1 cones. Type 3 cones resemble type 2, except that they have a clear vacuole, but not an oil droplet, in the inner segment. The pigment epithelium contains abundant phagosomes, but pigment granules are absent where the epithelium overlies the choroidal tapetum lucidum. Regular arrays of tubules occur in the cytoplasm, some of which appear to be formed from three interlacing hexagonal nets. Two types of bipolar cell are present. Most are displaced bipolars, with nuclei in the outer nuclear layer. The rest are large, with nuclei in the horizontal cell layer. Both types bear Landolt’s clubs, which penetrate the outer limiting membrane. Their endings contain a cilium complex, and a single large mitochondrion. Some contain 60 nm vesicles, which are also found near disrupted club endings. Two types of horizontal cell are present. A few dark-staining cells with extensive web-like processes occur next to the outer plexiform layer. The expansions of rod basal filaments make contact with these cells. More voluminous pale staining cells with long cylindrical processes occur vitread to the dark cells. Presumed amacrine cells form a layer vitread to the horizontal cells; they and the inner plexiform layer were not well fixed. Sparse ganglion cells occur at the same level as the nerve fibre bundles. Radial fibres penetrate the horizontal cell layer as compact columns. They do not contribute to the outer plexiform or horizontal cell layers, but elsewhere spread amongst the other retinal elements. Their expansions determine the inner contour of the retina. Cells, probably microglial, which contain lysosomes are scattered amongst the other elements. 143000 myelinated fibres are present in the optic nerve, which also contains non-myelinated fibres. Retinal cell counts are given.

Purification and properties of the cytosolic and mitochondrial forms of aspartate aminotransferase and malate dehydrogenase from rat heart

1987 ◽  
Vol 65 (3) ◽  
pp. 239-244 ◽  
Author(s):  
Charalampos Mavrides ◽  
Guylaine Nadeau
Keyword(s):  
Malate Dehydrogenase ◽  
Crude Extract ◽  
Aspartate Aminotransferase ◽  
Rat Heart ◽  
Pyridoxal Phosphate ◽  
Single Procedure ◽  
Purification And Properties ◽  
Michaelis Constants ◽  
Malate Aspartate Shuttle ◽  
Original Crude

The present work describes the purification from rat heart of the mitochondrial and cytosolic forms of the enzymes of the malate–aspartate shuttle, aspartate aminotransferase (EC 2.6.1.1) and malate dehydrogenase (EC 1.1.1.37), by a single procedure after the preparation of the original crude extract. In 10 purification steps, the four enzymes were obtained electrophoretically pure in yields ranging from 6 to 54% of their respective isoenzyme levels in the crude extract. Apoenzymes were formed from the aminotransferases by reacting them with cysteine sulfinate and dialyzing. Complete reconstitution was obtained after a brief incubation with pyridoxal phosphate. All four enzymes are dimers. The mitochondrial isoenzymes are of slightly lower molecular weight than their respective cytosolic forms. Michaelis constants and maximal velocities were derived by the use of primary and secondary plots. In general, the properties of the enzymes from rat heart are similar to the properties of the enzymes from other animal sources.

Synaptic organization of cone cells in the turtle retina

1971 ◽  
Vol 262 (844) ◽  
pp. 365-381 ◽  
Keyword(s):  
Horizontal Cell ◽  
Plexiform Layer ◽  
Intercellular Junctions ◽  
Bipolar Cells ◽  
Outer Plexiform Layer ◽  
Horizontal Cells ◽  
Synaptic Organization ◽  
Basal Surface ◽  
Cone Cells ◽  
Cell Processes

The intercellular junctions of cone pedicles in the turtle retina were studied electronmicroscopically in tissue prepared by conventional techniques or impregnated by the method of Golgi. Dendritic branchlets of bipolar cells make specialized contacts with the basal surface of the pedicles. Processes ending laterally to wedge-shaped projections (synaptic ridges) of the pedicles probably belong always to horizontal cells, and make proximal and distal (to the synaptic ridges) junctions with the pedicles. Processes ending opposite the apex of the synaptic ridges are engaged also in two kinds of specialized contacts, termed apical and distal junctions. Basal processes of the cone pedicles make specialized contacts with adjacent pedicles, and with unidentified processes at the outer plexiform layer; their endings abut upon horizontal cell processes lodged within the pedicles of other cone cells.

scholarly journals ACTIVITY OF MALATE-ASPARTATE SHUTTLE ENZYMES OF BULLS AND BOARS REPRODUCTIVE ORGANS AND EPIDIDIMAL SPERMATOZOA

2020 ◽  
Vol 21 (2) ◽  
pp. 86-89
Author(s):  
N. V. Kuzmina ◽  
D. D. Ostapiv ◽  
O. I. Chajkovska ◽  
R. D. Ostapiv ◽  
O. P. Panych
Keyword(s):  
Malate Dehydrogenase ◽  
Aspartate Aminotransferase ◽  
Protein Concentration ◽  
Tissue Specificity ◽  
Testicular Tissue ◽  
Reproductive Organs ◽  
The Body ◽  
White Breed ◽  
Dairy Breed ◽  
Malate Aspartate Shuttle

The activity of malate-aspartate shuttle enzymes in the reproductive organs and epididimal sperm of bulls and boars was studied. The research was conducted on bulls of the Ukrainian black-spotted dairy breed (n = 5; aged 14 - 16 months) and boars of the Great White breed (n = 3; aged 10 - 12 months). After slaughter, the testes and testicular appendages were removed and the spermatozoa were washed with 0.9% sodium chloride solution. Testicular and epididimal tissues were homogenized and centrifuged. Aspartate aminotransferase (AST), malate dehydrogenase (MDG) and protein concentration were determined in the supernatant and epididimal sperm. The specie and tissue specificity of aspartate aminotransferase and malate dehydrogenase activity have been established. In particular, in bulls, the activity of AST in the tissues of the testis, head and body of the epididymis of bulls is almost the same (116.5 - 118.3 nmol/min×mg of protein) and on 18.5 - 19.7% (р<0,05) higher in the tail of the appendix. In this case, MDG activity in the reproductive organs shows wavy changes: in the testicular tissue is high (1.96 ± 0.15 nmol / min × mg of protein), and in the epididymis: in the head is reduced (3.5 times ; p <0,001), increased in the body (p <0,05) and decreased again in the tail. In the sperm of bulls, the activity of AST from the head of the appendix - 69.3 ± 8.06 nmol / min × mg of protein, from the body - increased (p <0.05) and again (p <0.001) decreased from the tail of the appendix. MDG activity in sperm from the head of the epididymis was 0.50 ± 0.04 nmol/min×mg of protein, lower by 38.0% (p <0.05) from the body and 50.0% (p <0.001) higher in the tail. In boars, the activity of AST in testicular tissue - 20.3 ± 5.22 nmol / min × mg of protein and higher in the appendix: 45.6% - in the head, 59.0% - in the body and 64.0 % - in the tail. Similarly, the activity of MDG in testicular tissue was 0.22 ± 0.02 nmol / min × mg of protein, increases by 40.6% in the head and remained at the same level in the body of the appendix, and in the tail tissue above 2, 5 - 2.7 times (p <0.001). In bovine germ cells, the activity of AST and MDG from the body of the appendix was, respectively, 102.3 ± 6.1 and 13.20 ± 0.15 nmol / min × mg of protein, lowered twice (p <0,001) and 10.7 % in the head and more than four times (p <0,001) and 61,2% (p <0,001) in the tail of the appendix.

Reorganization of horizontal cell processes in the developing FVB/N mouse retina

2001 ◽  
Vol 306 (2) ◽  
pp. 341-346 ◽  
Author(s):  
Sung-Jin Park ◽  
In-Beom Kim ◽  
Kyu-Ryong Choi ◽  
Jung-Il Moon ◽  
Su-Ja Oh ◽  
...  
Keyword(s):  
Horizontal Cell ◽  
Mouse Retina ◽  
Cell Processes

scholarly journals Comparison of methods for obtaining doubled haploids of carrot

2017 ◽  
Vol 86 (2) ◽  
Author(s):  
Waldemar Kiszczak ◽  
Urszula Kowalska ◽  
Agata Kapuścińska ◽  
Maria Burian ◽  
Krystyna Górecka
Keyword(s):  
Plant Regeneration ◽  
Doubled Haploid ◽  
Aspartate Aminotransferase ◽  
Doubled Haploids ◽  
The Other ◽  
Plant Production ◽  
Comparison Of Methods ◽  
Anther Cultures ◽  
Induction Stage ◽  
Main Factor

Doubled haploid lines of carrot can be obtained through androgenesis in anther cultures and in isolated microspore cultures. The two methods were compared using three carrot cultivars (‘Kazan F1’, ‘Feria F1’, and ‘Narbonne F1’) at the androgenesis induction stage, during plant regeneration from embryos, and during acclimatization of androgenetic plants as well as their characterization. It was found that cultivar was the main factor affecting the efficiency at each stage of plant production in both anther and isolated microspore cultures. The efficiency of androgenesis in anther cultures of ‘Feria F1’ was considerably higher in comparison with isolated microspore cultures, and more plants were obtained from the embryos of androgenesis-cultured plants. In ‘Kazan F1’ and ‘Narbonne F1’, more acclimatized androgenetic plants were produced from anther cultures. Ploidy assessment of acclimatized plants of ‘Narbonne F1’ showed that the majority of the plants in the population derived from anther cultures had a doubled chromosome (DH) set. On the other hand, the majority of plants obtained from isolated microspore cultures were haploids. When assessing homozygosity, it was found among plants obtained in anther cultures that the percentage of homozygotes for phosphoglucose isomerase (PGI) and aspartate aminotransferase (AAT) depended on the cultivar. In contrast, the majority of plants derived from isolated microspore cultures were homozygous regardless of cultivar.

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