Trophic relationships and seasonal utilization of salt-marsh creeks by zooplanktivorous fishes

Synopsis In a high salinity estuary at North Inlet, South Carolina, co-occurrence and possible competition among adults of four dominant zooplanktivorous fishes were minimized by seasonal adjustments in lateral and vertical distributions as well as in dietary preferences. In winter, Atlantic silversides, Menidia menidia, occupied the entire water column while other planktivores were rare or absent from the estuary, and they consumed large prey such as mysid shrimps and fish larvae. An immigration of bay anchovies, Anchoa mitchilli, in the spring resulted in a redistribution of species with Atlantic silversides shifting to the surface waters and bay anchovies dominating the lower half of the water column. Both fishes consumed mostly copepods in the spring, but each favored a different species. There was little similarity in the large prey items consumed by the two fishes. Striped anchovies, Anchoa hepsetus, arrived in mid-summer and were most abundant at the surface while bay anchovies continued to dominate the bottom waters. Atlantic silversides were rare in all summer collections. The diets of the two anchovies were similar, but vertical separation during the period of maximum zooplankton abundance probably minimized competition. Rough silversides, Membras martinica, which were obligate surface dwellers, shared the upper water column with striped anchovies, but the two species had very different diets during their period of co-occurrence. Although seasonal changes in fish diets reflected shifts in zooplankton composition and all fishes consumed a variety of prey types, preferences for some prey taxa and total avoidance of others were indicated. Electivity indices indicated an especially strong selection for fiddler crab megalopae by all fishes in the summer and fall. All fishes, except rough silversides, which fed almost exclusively on copepods and crab zoeae, consumed large prey items when they were available. Fine scale partitioning of the food resources was apparent in the selection of different copepod and insect species by the fishes. Spatial and temporal separation in the distribution and/or dietary preferences of the zooplanktivores fishes probably reduces the potential for resource competition. Given the high abundances and selectivity of the planktivores, significant impacts on some zooplankton populations probably result.     

Active site kinetics of horse serum cholinesterase

Horse serum Cholinesterase hydrolyzes choline and p-nitrophenol esters at different rates. Deacylation and acylation seem to be the rate-limiting step for charged and uncharged substrates respectively. Activation energy is similar for the acetic, propionic, and butyric esters of thiocholine, but it is higher for p-nitrophenylpropionate. Inhibition by the tetramethyl-ammonium ion is competitive. Tetraethyl-, tetrapropyl-, and tetrabutyl-ammonium ions are mixed-type inhibitors. The pH studies demonstrated the existence of a residue, pK = 6.33, involved in catalysis.     

Ultrastructural changes in Blastomyces dermatitidis after in vitro exposure to lidocaine

Electron microscopic examination of yeasts of Blastomyces dermatitidis, exposed in vitro to concentrations of lidocaine that occur when the drug is used for topical anesthesia, showed that lidocaine rapidly damaged intracellular structures. The extent of damage was dependent on the concentration of drug and length of exposure. The observed ultrastructural changes were very similar to those reported for other drugs that directly damage membranes. This relationship suggests that the antifungal effect of lidocaine is the result of direct membrane damage.     

Nitrogen fixation efficiency,natural15N abundance,and morphology of mesquite (Prosopis glandulosa) root nodules

Summary The relative nitrogen fixation efficiencies (RE 1-[H₂ evolved÷C₂H₂ reduced]·100) of four mesquite (Prosopis glandulosa var.torreyana) rhizobia (Strains WR 1001, WR 1002, L5, L9) and a cowpea rhizobia (Strain 176A32) on mesquite were evaluated in a glasshouse experiment. Plant yield, shoot N accumulation, and the natural¹⁵N abundance (¹⁵N) of nodule tissue were determined. Strain WR 1002 failed to nodulate mesquite and strain L5 produced ineffective nodules. Among the three effective strains (WR 1001, L9, 176A32) the cowpea strain (176A32) and strain L9 had significantly higher RE than strain WR 1001. Differences in RE, however, were not accompanied by significantly higher plant yield and shoot N accumulation. The difference in¹⁵N abundance between foliar tissue and nodules (nodules minus leaves) was 0.47 ¹⁵N for the ineffective L5 nodules, while for the effective WR 1001, L9, and 176A32 nodules, respectively, this difference was 8.35, 7.81, and 8.35 ¹⁵N. This indicates a similar relationship between N₂-fixing effectiveness and natural¹⁵N enrichment of nodules that was previously observed in soybeans (Glycine max, L. Merr.). Strains WR 1001 and L9 produced elongate, indeterminate nodules typical for mesquite. The ineffective L5 nodules had few infected cells and an abundance of cortical amyloplasts. Mesquite nodules produced by the cowpea strain were spherical and were somewhat more similar in internal morphology to determinate nodules typical of cowpea than indeterminate nodules normally associated with mesquite.     

Localization and Substrate Specificity of Glycosidases in Vacuoles of Nicotiana rustica

Vacuoles isolated from Nicotiana rustica var brasilia have been shown to contain significant levels of glycosidase activity when assayed using p-nitrophenyl-glycosides as substrates. The substrate specificity for the glycosidases in the vacuolar fraction closely paralleled that found in the protoplasts, and the leaf tissue from which the vacuoles were isolated. The substrate specificity of the vacuolar enzyme(s) was different from glycosidic activity found in the commercial digestive enzyme preparations used to isolate the protoplasts from leaf tissue. It was demonstrated that 70 to 90% of the glycosidases that were found in the protoplasts appeared to be localized within the vacuole, when the p-nitrophenyl substrates α- and β-;d-galactose, β-d-glucose, and α-d-mannose were used. Neither the vacuolar nor the protoplast enzymes were active towards the naturally occurring phenolic glycoside, rutin. α-Mannosidase appears to be a valuable marker enzyme for vacuoles isolated from mesophyll leaf cells of tobacco.     

Inflammatory cells in solid murine neoplasms. IV. Cytolytic T lymphocytes isolated from regressing or progressing Moloney sarcomas.

Highly purified suspensions of intratumoral T lymphocytes, recovered 11 and 13 days after induction of regressing or progressing Moloney sarcomas, were compared in their ability to lyse specifically the MSC cells used for tumor induction. Cytolytic activity, expressed in terms of lytic units/10(6) T cells, was similar for intratumoral T cell suspensions obtained 11 days after induction of either regressing (3.1 +/- 1.3 LU/10(6) T cells) or progressing (4.3 +/- 1.8) neoplasms. By 13 days post-induction, regressing tumors contained T lymphocytes with an increased cytolytic activity (11.1 +/- 4.5) whereas those from progressing tumors were strikingly less able to kill MSC cells (less than or equal to 0.2). This dramatic loss in cytotoxicity could not be attributed to errors associated with the enzymatic disaggregation method, inhibition by copurified endogenous tumor cells, or immunosuppression induced by viral infection. The changes in functional activity of intratumoral T lymphocytes from the two types of sarcoma appeared to be correlated with the stage of neoplasia. In this model system, cytolytic activity of T lymphocytes increased during spontaneous tumor regression whereas losses in cytotoxicity occurred coincident with the onset of inexorable progression.     

Liquid preservation of highly purified human granulocytes

Highly purified human granulocytes isolated from continuous flow centrifugation leukapheresis concentrates by counterflow centrifugation-elutriation were stored at 4 °C in concentrations of 6 × 10⁶ to 1 × 10⁷ granulocytes per milliliter for up to 14 days. The in vitro physiological function assays of phagocytosis, oxygen consumption associated with phagocytosis, bacterial growth inhibition, chemotaxis, and five enzyme analyses indicated good storage survival for up to 4 days. Stored granulocytes separated from other blood cells have greater storage stability than granulocytes stored as leukapheresis concentrates. After 14 days of storage a small percentage of granulocytes still maintained all physiological functions, with the exception of chemotaxis. Of the five enzymes assayed, only the enzyme activity of leucine aminopeptidase decreased significantly by the 14th day of storage. The storage stability of each physiological function assayed decreased as follows: bacterial growth inhibition (most stable), phagocytosis, oxygen consumption, and chemotaxis (least stable).