Bernard C. Abbott

Eye Structure and the Classification of Stomatopod Crustacea

The cornea in most stomatopods is divided into two halves by a band of specialized ommatidia, the middle band. This band is absent in the Bathysquilloidea, but present in the three other superfamilies. It is two facets wide in the Squilloidea and six facets wide in the Lysiosquilloidea and Gonodactyloidea. This differentiation must have occurred very early in the evolutionary history of the group.

Creatine and the control of energy metabolism in cardiac and skeletal muscle cells in culture

Abstract The addition of creatine to the culture media in which either cardiac or skeletal muscle cells were grown resulted in an increased concentration of intracellular phosphorylcreatine. Since the only metabolic path known for the synthesis of phosphorylcreatine is via creatine phosphokinase, it is suggested that the mitochondrial enzyme activity was stimulated by creatine, and that the ADP formed as a product of the reaction became available for the oxidative phosphorylation. The rate of synthesis of ATP must have been stimulated prior to the net increase in phosphorylcreatine. This finding provides evidence that creatine might be involved in a regulatory feedback mechanism maintaining the energy source for contraction and not serving merely as an energy store in the muscle.

STRUCTURE AND OPTICS OF OMMATIDIA FROM EYES OF STOMATOPOD CRUSTACEANS FROM DIFFERENT LUMINOUS HABITATS

Shapes and sizes of ommatidia in six genera of stomatopods from different luminous habitats are described. Cornea-cone apertures and acceptance angles have been calculated. The ommatidia belong to the apposition type with fused rhabdoms as in most Malacostraca, but the spindle-shaped cone and the transparent wedges under the cornea are acquisitions of stomatopods. The same is true for rhabdom specializations, especially the thin undulated rhabdoms in ommatidia of the six-row middle band of the Gonodactyloidea, that divides the eye in two halves. Several regions can be distinguished in stomatopod eyes by differences in shapes, sizes, and proportions of their ommatidia and by the skewing pattern along the columns of ommatidia. As more light becomes available in the habitat, apertures and acceptance angles seem to decrease mainly by increasing the lengths of the cones.

CORNEA SHAPE AND SURFACE STRUCTURE IN SOME STOMATOPOD CRUSTACEA

ABSTRACT Three types of eyes have been observed in three different lineages of the Stomatopoda. In the Gonodactyloidea and the Squilloidea, the cornea is divided into two halves by a line of specialized ommatidia, the middle band. This band is two facets wide in the squilloids, and occupies a small portion, about 4 per cent, of the surface area of the cornea. In gonodactyloids the band is six facets wide and occupies much more of the surface area of the cornea, between 15 and 38 per cent. The middle band appears to be absent in the bathysquilloids. The greater development of the middle band in the gonodactyloid lineage than in the other lineages may be related to binocular vision and the strike of the raptorial appendage, light available in the habitat, and/or the complex behavioral patterns developed by some members of this group.

Possible monocular range-finding mechanisms in stomatopods from different environmental light conditions

Abstract 1. 1. Stomatopods have double eyes. 2. 2. In the middle band dividing the two halves of the eye ommatidia are perpendicular to the cornea. 3. 3. Rows of ommatidia parallel to the middle band have divergent optical axes. 4. 4. In the columns across the middle band the optical axes of ommatidia near the middle band are convergent between the two halves of the eye. 5. 5. From the fifth to tenth ommatidium towards the sides optical axes on each side are parallel to each other and to those in the middle band. 6. 6. This results in a strong overlap of visual fields between ommatidia with parallel optical axes in each half of the eye and with the fields of the skewed ommatidia from the opposite half of the eye. 7. 7. We postulate this as the morphological basis for a range-finding and motion measuring device along the columns, repeated around the eye along the rows. 8. 8. We hypothesize that this device may measure distances by the amount and pattern of overlap of visual fields at each point in space. 9. 9. Species from bright light habitats show less skewed ommatidia and similar patterns of overlap are shifted to longer distances than in dim light species.

An Attempt to Correlate Pseudopupil Sizes in Stomatopod Crustaceans with Ambient Light Conditions and Behavior Patterns

Abstract 1. 1. The distribution of pseudopupils in the eyes of representatives of five genera of Stomatopoda has been studied. 2. 2. A triple pseudopupil is seen when the eye is viewed perpendicularly to the specialized middle band on the cornea, but a double pseudopupil appears when the direction of viewing is moved five degrees away from the vertical, as a result of the skewing of ommatidia adjacent to the middle band. 3. 3. Skewed ommatidia near the middle band constitute a monocular range-finder. 4. 4. Species with the most complex behavior patterns have the most complex skewing patterns of ommatidia.

Gibberellic Acid: A Growth Factor in the Unicellular Alga Gymnodinium breve

Gibberellic acid stimulates growth in the unicellular alga Gymnodinium breve (dinoflagellate). The maximum effect was obtained with 10-7 molar gibberellic acid, whereas concentrations greater than 5 x 10-7 mole per liter were inhibitory. The effect of the compound is observed as a marked shortening of the lag period, which is normally 6 to 8 days after innoculation.

The effect of adenosine on cardiac cells in culture

Abstract Chronotropic effect of 5 × 10−6 m to 5 × 10−5 m -adenosine on beating rat heart cells in culture was demonstrated. Concomitant with the increased rate of rhythmic contractions was a 50% increase in the intracellular ATP concentration, a net synthesis of c. 15 nmol ATP/mg protein. This net change in concentration was a result of a new high steady state of ATP synthesis and not of a transphosphorylation from phosphorylcreatine, as the latter remained at control levels. The rhythmic contractions and the increased ATP synthesis in the presence of adenosine were inhibited by oligomycin + 2-deoxyglucose and 1-fluoro-2,4-dinitrobenzene The excitability of the cardiac cell membrane correlates with a continuous synthesis of ATP.

A stereological analysis of the effect of adriamycin on the ultrastructure of rat myocardial cells in culture

Abstract Adriamycin is an effective anti-cancer agent which produces a dose-dependent, irreversible cardiomyopathy of unknown etiology in a significant number of cancer patients. The effect of adriamycin on the ultrastructure of cultured mammalian myocardial cells was examined with light and electron microscope stereological analysis. Cell surface/cell volume, nuclear volume/cellular volume, and nuclear volume/sarcoplasmic volume ratios did not change after adriamycin treatment, showing that the cell volume and sarcoplasm volume were not altered. The nuclear surface area relative to both the nuclear volume and cellular volume was greater in adriamycin-treated cells, implying increased nuclear pleomorphism. The percent of myocardial sarcoplasm occupied by the mitochondria increased very significantly subsequent to adriamycin treatment. That the mitochondria increased in size was indicated by the unchanged mitochondrial surface/cell volume ratio and the decrease in the mitochondrial surface/volume ratio. A significant decrease in glycogen content after exposure to adriamycin as revealed by electron microscope stereological analysis was also observed with the light microscope. Subsequent to adriamycin treatment a small fraction of the cells died and detached from the plate.

Cytochalasin B: Effect on mammalian cardiac muscle cells in culture

Abstract The effect of cytochalasin B on mammalian cardiac cells in culture was studied at 1 μg/ml and 5 μg/ml cytochalasin B. When cells were grown in the presence of cytochalasin B their morphology was altered and cytokinesis inhibited, but the cells continued to contract, often at an increased rate. The adhesiveness of the cells to the culture dish was increased, suggesting a membrane effect of cytochalasin B, rather than an effect on the contractile machinery.