Adhesive apparatus in certain Indian hill stream fishes

The results of a detailed study on the adhesive apparatus of Indian hill stream cyprinid and sisorid fishes are presented. The structure of the mental suctorial disc in the genus Garra is described. Histological study of the mental region of Crossocheilus and Psilorhynchus has also been made and compared with the mental disc of Garra . The muscles of the disc which control its movements in bringing a partial vacuum during adhesion have been investigated. The complexity of the geniohyoideus muscles in Garra is interesting. Variations in the degree of development and histological modifications of the mental disc are exhibited by the fishes of the genus Garra .
A thoracic adhesive apparatus in the form of longitudinal or transverse ridges and grooves is present in the sisorids, Laguvia, Glyptothorax and Pseudecheneis except Gagata . A close study has revealed that the adhesive apparatus of the catfishes works mainly on the principle of friction. The variations in shape, size and location of the adhesive apparatus in various species are correlated to their respective habitats.
Structural variation in the adhesive apparatus of Pseudecheneis is maximum in comparison to that in Laguvia and Glyptothorax . It is discovered that the modifications are associated with the presence of multi-spinous layers, formation of caps by the basal or holdfast cells and with the transformation of loose areolar tissue into thick collagenous dermis. The presence of a pad of adipose tissue in the region of the adhesive apparatus has been reported and its physiological significance as a source of stored food suggested.
The anterior part of the protractor ischii muscle is modified to control the action of the adhesive apparatus. In Pseudecheneis , besides the m. protractor ischii, the ventral part of m. mesioventral is also associated with the adhesive apparatus.     

Comparison of Direct Plating Media for the Isolation and Enumeration of Enterococci in Certain Frozen Foods

A total of 15 agar media were examined for their yield, selectivity, readability, and simplicity of preparation and use. A thallium medium of Barnes was selected as the better of the high yield-fair selectivity type of medium and an azide-citrate medium of Reinbold appeared to be the better of the low yield-high selectivity type of medium. Sodium carbonate (optimal concentration, 0.20%) was found to increase recovery substantially when added to certain media, especially in the presence of 0.05% Tween 80. When these two ingredients were incorporated into a medium modified after Slanetz and Bartley, the resultant medium was superior to other media for the isolation and enumeration of enterococci in certain frozen foods, such as peas and hamburger, by the direct plating method.     

Freezing-Out Technique Applied to the Concentration of Biologically Active Materials

When applied to a dilute solution of folic acid and glucose, a freezing-out (with agitation) technique was shown to be an effective method of achieving a 20-fold reduction in volume with a loss of 10% of the active material being concentrated. Concentration of a stimulatory factor for Lactobacillus casei produced by Candida albicans in a complex medium was limited by the total solute concentration. Salts in the medium were concentrated to levels inhibitory for L. casei. The process is not selective and all solutes are concentrated.     

Electron Microscope Study of Lens Fibers

Comparative electron microscope investigations on sections of the lens cortex of the normal, mature rat, rabbit, monkey, and the normal calf reveal similar patterns of intracellular organization. The superficial lens fiber contains a nucleus, mitochondria, endoplasmic reticulum, dense granules, Golgi complex, and a quantity of small structures of low opacity which appear as filamentous and spherical configurations. Variations in number, distribution, and spatial arrangement of cytoplasmic elements in lens fibers are described. These changes in the pattern of cytoplasmic organization are concomitant with development of fibers and their displacement towards the center of the lens. Structural details of the various zones of the lens epithelium and the lens fibers are compared.     

Studies with cyanidium caldarium,an anomalously pigmented chlorophyte

Summary Cyanidium caldarium, an alga found in acid hot springs troughout the world, has a morphology and developmental history resembling those of Chlorella, but contains C-phycocyanin and no chlorophyll other than chlorophyll a. The reasons for considering it to be a member of the Chlorophyta are reviewed. Cyanidium is also remarkable for its thermal and acid tolerance. It grows readily in the dark on sugar media. However, light is required for the formation of chlorophyll and phycocyanin except in occasional variant cells which can form limited amounts of these pigments in the dark. Light-grown Cyanidium carries out normal green plant photosynthesis but resembles the red and some of the blue-green algae in that chlorophyll-absorbed light is used with lower efficiency than that absorbed by phycocyanin.The possible significance of the unusual pigmentation of Cyanidium is discussed.Contribution no.23 from the Laboratory of Comparative Physiology and Morphology of The Kaiser Foundation.     

Automatic search for model to simulate the differentiation of T lymphocytes within the thymus

The differentiation of T Lymphocytes within the thymus is an important biological phenomenon during wich these cell acquire their functions to further control the immune system. Numerous experiments under various conditions have been devised to understand the different mechanisms involved in this complex process. Nevertheless, interpretation of these experiments lead to still contradictory debatable hypotheses. Modelisation of this process through classical simulation methods cannot be envisaged because they are not adapted to modifications of the model structure, which is the point of interest. For these reasons, we proposed a new approach of automatic search for model. The program consists of four independent connected modules : The generator produces model, based on the rationale of formal grammars. Protocol and experimental data are stored in a set of experiments. The simulator using a protocol and a model provides simulated results. Finally, the supervisor by comparing simulated results and experimental data, adapts the model parameters to increase their fit and either chooses a new experiment to explore, or modifies the model structure. Change of the model structure is performed among still unexplored models according to their promise level, which is iteratively evaluated relatively to previously explored models through a proposed model distance. The generator is written in Prolog and the other modules in C++. The architecture of the program allows us to modify or complete a module without changing anything in the other modules. As a consequence, the proposed modeling approach conceived to study T lymphocyte differentiation within the thymus remains independent of this biological phenomenon and can be applied to other biological problems.     

Phenotypic variation during micropropagation of the chimeralRhododendron ‘President Roosevelt’

The putative periclinal chimeraRhododendron xlimbatum President Roosevelt was used to study the origin of shoots in vitro. Genotypic segregation readily occurred in vitro. Numerous phenotypes were observed, although most shoots were either entirely green or maintained the original variegation pattern. Derivatives of the third apical layer were rarely involved in shoot formation. A reversed chimeral form was isolated. Adventitious shoots were usually miniaturized and rapidly proliferating, but axillary shoots had thicker stems, larger leaves and proliferated more slowly. Corolla tissue produced stunted, leafy shoots; no variegated shoots were produced from floret explants. In shoot tip cultures the addition of 40M 2iP without IBA resulted in the greatest number of shoots. Explant choice was the most critical factor for maintenance of foliar variegation.