Factors affecting zooplankton feeding by the sea anemoneAiptasia pallida

Effects of various treatments on prey capture, prey ingestion and ingestion time of individualArtemia salina nauplii by the sea anemoneAiptasia pallida Verrill were studied in the laboratory. Exposure to crudeArtemia homogenate, 5 × 10^–4 M reduced glutathione or 5 × 10^–4 M proline significantly decreased the number ofArtemia that were captured and ingested but had no significant effect on the ingestion time of individualArtemia. Multiple captures increased the total ingestion time but decreased ingestion time per prey item. Results suggest that, under these conditions, the prey capture phase of zooplankton feeding was somewhat distinct from the ingestion phase since chemical stimuli that significantly reduced prey capture had no significant effect on ingestion time.     

Psychosomatic symptoms,stress, and modernization: A model

The quantity of research on the effects of stress on disease has increased substantially in recent years, but little effort has been devoted to examining the effects of cultural influences in the stress process. A model is proposed in this paper in which cultural context exerts a modifying influence on the relationship between sociocultural stressors and psychosomatic symptoms, specifically in the context of modernization. In change situations involving increasing modernization there is increased differentiation in systems of social stratification within a community, due to increased potential for upward social mobility. The individuals who are upwardly mobile adopt a particular style of life, involving the acquisition of western consumer goods, as symbolic of their success. Lower class individuals strive to attain this same style of life as a claim to a higher status social identity, but their lower economic condition results in stressful incongruities and higher psychosomatic symptoms. Individuals who are successful in upward mobility are confronted by a different set of stressors that are primarily intrapsychic in nature. Events and circumstances perceived as threats to their self-identity are related to more psychosomatic symptoms. Thus, the meaning of specific stressors changes depending on the sociocultural context of the individual, and this meaning serves as a bridge between environmental circumstances and physiological outcomes. This model receives substantial empirical support in two field studies. Limitations of the model and implications for future research are discussed.Research in St. Lucia was supported by the Connecticut Research Foundation and the University of Connecticut Health Center. Research in the U.S. was supported by Research Grant MH 33943 from the Center for the Study of Minority Group Mental Health, National Institute of Mental Health. Drs. Arthur Kleinman, Lee Badger, H. B. M. Murphy, James Bindon, and Laurence Watkins kindly commented on previous drafts of this paper. Dr. Michael Murphy deserves a special note of gratitude for reading several drafts of the paper and for patiently sitting through several lengthy discussions of it. I alone am responsible for the errors and shortcomings.     

The anatomy of tissue cultured red raspberry prior to and after transfer to soil

The leaf, petiole, stem and root anatomy of an aseptically cultured red raspberry clone (Rubus idaeus L.) was studied before and 5 weeks after transfer to soil under controlled environmental conditions. Tissues persistent from culture showed little or no change with time in soil; they grew minimally and slight secondary wall deposition occurred. New organs formed in successive weeks after transplantation showed a graded increase in potential size and development. Some features, such as collenchyma formation, rapidly returned to control levels; this was seen in new leaves expanding in the first week after transplantation. Other features, such as sclerenchyma formation, did not occur in leaves expanding during the first 2 weeks after transplantation, even when these were a month or more in age. Some sclerenchyma was seen in leaves expanding in the third week after transplantation, increasing in later-formed leaves. Increasing the light intensity of transplant accelerated the return to control-type organ size and appearance. During acclimatization transitional forms of leaves, petioles, stems and roots develop that ranged anatomically from culture-to control-type. This trend is analagous to the normal developmental sequence of organ formation as it affects the potential for development of successily formed organs.     

Metabolic inhibition of size-fractionated marine plankton radiolabeled with amino acids,glucose, bicarbonate,and phosphate in the light and dark

The effects of various metabolic inhibitors (dichlorophenyl dimethylurea, chloramphenicol, cycloheximide, carbonyl cyanide m-chlorophenyl hydrazone) on the accumulation of radiolabeled substrates (amino acids, glucose, bicarbonate, phosphate) by size-fractionated marine microbial plankton from the Sargasso Sea and the eastern Canadian arctic were studied in time-course fashion during experimental incubations either exposed to or shielded from ambient solar radiation. Picoplankton accounted for 65% of the organic substrates and phosphate accumulated by the assemblages. The rate of organic substrate accumulation was stimulated by solar radiation in some cases but inhibited in other cases. Presumably, stimulation and inhibition co-occur and the measured response is the net result arising from these counteracting tendencies. Approximately 40% of H¹⁴ CO₃ ^– accumulation in the Sargasso Sea was associated with the picoplankton. The insensitivity of picoplankton¹⁴C-labeling to cycloheximide suggested active prokaryotic photosynthesis rather than heterotrophic assimilation of¹⁴C-labeled algal photosynthates as the route of labeling. The usefulness of some inhibitors was restricted in this study because of inconsistent correlations between the intended primary metabolic effect and the measured ecological response within the duration of the experiment.     

Changes in density of DNA after interaction with dipicolinic acid and its possible role in spore heat resistance

We examined the effect of interacting dipicolinic acid and its calcium chelate on the wet and dry density of DNA. Complexes are produced whose densities are different from those of the individual components. Also, we observed two modes of binding, one strong the other weak, between DPA or CaDPA and DNA. The strength of the binding modes was reflected in the rate of dissolution of the complexes as monitored by changes in wet density with time and temperature. We conclude from these and other data in the literature that the interaction of dipicolinic acid with DNA not only influences the spore wet density and the ratio of core/core⁺ cortex volume, but may also influence the spore heat resistance.     

Characteristics of bacterium GB-2, a presumptiveCytophaga species with novel immunoregulatory properties

A Gram-negative, psychrophilic bacterium, designated GB-2, was isolated from fetal calf serum and analyzed for its morphological, physiological, and biochemical characteristics. Gliding motility, sensitivity to actinomycin D, the presence of the pigment flexirubin and cytochrome c, growth on a variety of carbohydrates, the production of acid fermentation products, and a 34.9 mol% guanine+cytosine (G+C) content of bacterial DNA indicate GB-2 to be a member either of the generaCytophaga orFlexibacter. Growth of GB-2 was optimized in a simple defined medium to facilitate isolation and characterization of bacterial products. Liquid growth of GB-2 resulted in the release of significant quantities of a macromolecule free of both endotoxin and protein into the growth supernatant, which activated the proliferation of murine lymphocytes. The relationship between this bacterium and its end-products to other species of theCytophaga/Flexibacter group is discussed.