Uptake of l-Phenylalanine in Synchronous Chlorella fusca. Characterization of the Uptake System

Phenylalanine uptake in Chlorella fusca was measured, using the membrane filter technique. The cells were synchronized, and harvested at specific points of the life cycle. Experiments with autospores showed that the uptake followed saturation kinetics, with a K_m= 5 μM. V_max, was 0.1 nmol/min × 10⁷ cells. The optimum temperature for the uptake was 40°C, and the activation energy was 1700 J/mol. The uptake showed a high specificity towards l -phenylalanine; presence of the unlabelled stereoisomer did not inhibit the uptake. Uptake of l -phenylalanine was inhibited in the presence of other analogues or other amino acids, but only if they were present in concentrations considerably higher than that of L-phenylalanine. Variations in the ratio of Na4⁺ to K⁺ in the external solution during uptake experiments did not have any influence upon the uptake rate of l -phenylalanine. The cells were able to take up the amino acid against a concentration gradient. At pool maximum the ratio between internal and external amino acid concentration was 1000/1. 2,4-Dinitro-phenol inhibited the uptake completely. Exchange between internal and external l -phenylalanine could not be demonstrated. The K_m value did not change during the life cycle of the cells. The uptake rate reached a maximum at the end of the light period, and fell to a minimum just before sporulation started. It is concluded that Chlorella fusca cells have a highly specific, active uptake system for l -phenylalanine. The system is constitutive, independent on the K or Na concentration, and the mechanism of uptake does not change during the life cycle of the cells.     

Learning and perception of oddity problems by lemurs and seven species of monkey

Eight nonhuman primate species were compared in three experiments utilizing the oddity paradigm. The sample included 4 lemurs (Lemur catta), 26 Old World Monkeys (Macaca mulatta, M. nemestrina, M. speciosa, andCercopithecus nictitans) and 21 New World Monkeys (Cebus apella, Lagothrix humboldti andSaimiri sciurea). EveryS was first trained 60 days on “outside oddity” problems. Next,Ss solved “outside” oddity problems constituted from two short and two tall cylinders, and were tested for their perception of oddity withDavis andMcDonald's (1962) technique of varying the height of the centerplaced but nonreinforced stimulus. In the final experiment,Ss were given ambiguous oddity problems that could be solved either for form or color cues, andEs recorded preference. Cebus and woolly monkeys formed oddity learning sets as well as or better than any of the Macaque monkeys, but relatively poor performances were made by squirrel monkeys, spotnose monkeys, and lemurs. Woolly monkeys were outstandingly accurate in their perception of oddity based on changing stimulus height, no other species approaching them in this skill. Old World Monkeys were much more likely than New World Monkeys to use color as a cue.     

A function-associated molecule on rat natural killer cells identified by anti-idiotypic monoclonal antibodies.

Monoclonal antibodies were generated against idiotopes on an NK target antigen-specific IgM monoclonal antibody (mab). This mab (18C2) was originally produced against (NC-37) human EBV-transformed B cells. The 18C2 mab inhibits natural killer cell lysis of NC-37 and other target cells by preventing conjugate formation. Anti-18C2(id) mabs were tested for binding to effector cells and screened by ELISA, flow cytometry, and by inhibition of NK cytotoxicity. Two of the anti-18C2(id) (anti-id) mabs (12H1.C5 and 6D9.B11) were chosen for further study. The idiotypic specificity of these anti-id mabs was confirmed by testing their binding to 18C2 hybridoma cells in the presence of homologous and heterologous "cold" inhibitor mabs. Experiments were also conducted to determine the functional properties of these mabs. Anti-18C2(id) mab 12H1.C5 inhibited the cytotoxic activity of rat splenic NK (nylon wool nonadherent cells, NWNA) and rat ALAK cells. Flow cytometric (FCM) analysis of the binding of the anti-18C2(id) mabs demonstrated that mab 12H1.C5 bound 75.43% rat NWNA spleen cells, 43.74% rat ALAK cells, and 74.33% rat CRC- cells. Anti-id mab 6D9.B11 bound 45.20% NWNA cells, 70.45% rat ALAK cells, and 55.86% CRC- cells. Two-color FCM analysis demonstrated that the anti-id mabs not only bound to the same molecule on NK cells, but also these mabs bound to the same molecule as 5C6, an anti-NK cell mab. Biochemical analysis of the antigen recognized by mab 12H1.C5 was determined by Western blotting. The determinant on NWNA cells recognized by mab 12H1.C5 had an M(r) of 40 kDa and appeared to be identical to that recognized by mab 5C6. The same experiment using a transformed rat RNK-16 (CRC-) cell extract and Western blot analysis, demonstrated an M(r) of 42 and 48 kDa in the presence of mabs 5C6 and 12H1.C5. Monoclonal antibody 5C6 was previously shown to recognize a vimentin-like function-associated molecule on NK cell membranes. The anti-id mabs were also shown to have cross-reactivity with the intermediate filament vimentin as determined by Western blot analysis.     

Detection of function-associated molecules on rat NK cells and their role in target cell lysis.

Anti-effector cell mAb 5C6.10.4 (5C6) inhibits cytotoxic activity of fish nonspecific cytotoxic cells (NCC). We now show that 5C6 also inhibits mammalian NK cell activity using fresh and cultured (CRC) leukemic rat NK cells. The inhibitory activity of 5C6 was caused by blocking of conjugate formation between NK cells and YAC-1 targets. Binding studies done by flow cytometry (FCM) showed that mAb 5C6 specifically bound to 8% of unfractionated rat spleen cells. Enrichment by nylon-wool fractionation produced 27.2% specific binding, along with a 3.4-fold enrichment in cytotoxic activity. Tissue distribution studies revealed that the highest number of cells recognized by mAb 5C6 were found in NWNA spleen cells (28.7%), followed by liver (18.9%) and peripheral blood (13.9). Two-color FCM showed that although all 3.2.3 mAb-positive cells were also stained with mAb 5C6, a small percentage of 3.2.3. negative noncytotoxic NWNA spleen T cells were 5C6 positive. Redirected lysis experiments demonstrated that anti-effector mAb-producing myeloma cells could be killed by CRC and NWNA spleen cells. In addition, mAb 5C6 produced specific inhibition of redirected lysis of each myeloma target. Experiments were also conducted to determine the signaling capability of the FAM complex. Binding of the anti-FAM mAbs to NWNA rat spleen cells caused a rapid increase in cytosolic free calcium of approximately 472 nM. Western blot analysis of CRC cell lysates showed that the molecules recognized by anti-FAM mAbs have molecular weights of 38 and 42 kDa. These studies indicate that the anti-effector mAbs recognize a functionally relevant molecule on rat NK cells that is involved in the first steps of cytolysis, i.e., antigen recognition, and which also triggers the activation of signal-transducing events in these cells.     

The alpha protein ICP0 does not appear to play a major role in the regulation of herpes simplex virus gene expression during infection in tissue culture.

The herpes simplex virus type 1 (HSV-1) alpha protein ICP0 trans-activates HSV-1 early genes in transient expression assays. To investigate the function of ICP0 during HSV-1 infection, we have lowered the level of ICP0 by use of a recombinant plasmid that has been engineered to express the antisense message. Cell lines were constructed which stably carry the antisense plasmid. Total protein profiles from infected antisense cell lines showed that the level of ICP0 was reduced to less than 10% of the wild type level in two of the cell lines. However, reducing the level of ICP0 did not have a significant effect on the expression of HSV-1 early or late genes. The polypeptide patterns for the remaining infected cell polypeptides were similar in that no bands were absent although there were some quantitative differences. The level of two early proteins, glycoprotein B and glycoprotein D was reduced in one of the cell lines, however, levels were nearly equivalent to the control infection for two other cell lines tested. Virus yields were the same for the antisense cell lines and for parent cells. Decreased ICP0 levels did not lead to more restrictive phenotypes for an alpha 4 or alpha 27 mutant as protein patterns were similar for these mutants in antisense and parent cells. Therefore, while ICP0 has been demonstrated to be a strong inducer of gene expression in transient expression assays, it does not appear to have a major role as an activator during the productive infection of tissue culture cells.     

Contrasting levels of genetic differentiation among putative neutral microsatellite loci in Atlantic herring Clupea harengus populations and the implications for assessing stock structure

Porifera is a primarily marine phylum comprising more than 15,000 species. The successful and wide adaptive radiation of freshwater sponges (Haplosclerida: Spongillina) has resulted in the colonization of an extremely wide variety of habitats at all latitudes. Colonization is dated back to the Mesozoic, and the mono- or poly-phyletism of Spongillina, and the number of potential sponge invasions into freshwater is still under debate. Living freshwater sponges belong to 45 genera in six families for a total of 219 species. The highest diversity, at the scale of zoogeographic regions, is recorded from the Neotropical (65 species), Palaearctic (59 species), and Afrotropical regions (49 species). Endemic freshwater sponge species are 103 (47%) out of 219. All species belonging to the families Lubomirskiidae, Metschnikowiidae, and Malawispongiidae are endemic. Endemic species among the other families are 72% for Potamolepidae, 38% for Spongillidae, and 32% for Metaniidae. Data on some wide geographic areas are scattered and fragmentary if not almost completely lacking. Species richness is probably underestimated and doubtless destined to increase with further research. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Loss of functional Dicer in mouse radial glia cell-autonomously prolongs cortical neurogenesis

Radial glia of the mouse cerebral cortex emerge from neuroepithelial stem cells around embryonic day 11 and produce excitatory cortical neurons until a few days before birth. The molecular mechanisms that regulate the end of cortical neurogenesis remain largely unknown. Here we investigated if the Dicer-dependent microRNA (miRNA) pathway is involved. By electroporating a cre-recombinase expression vector into the cortex of E13.5 embryos carrying a conditional allele of Dicer1, we induced mosaic recombination causing Dicer1 deletion and reporter activation in a subset of radial glia. We analysed the long-term fates of their progeny. We found that mutant radial glia produced abnormally large numbers of Cux1-positive neurons, many of which populated the superficial cortical layers. Injections of the S-phase marker bromodeoxyuridine between postnatal days 3 and 14 showed that much of this population was generated postnatally. Our findings suggest a role for Dicer-dependent processes in limiting the timespan of cortical neurogenesis.     

Hormones and acoustic communication in anuran amphibians

Circulating hormone levels can mediate changes in the quality of courtship signals by males and/or mate choice by females and may thus play an important role in the evolution of courtship signals. Costs associated with shifts in hormone levels of males, for example, could effectively stabilize directional selection by females on male signals. Alternatively, if hormone levels affect the selection of mates by females, then variation in hormone levels among females could contribute to the maintenance of variability in the quality of males' signals. Here, I review what is known regarding the effects of hormone levels on the quality of acoustic signals produced by males and on the choice of mates by females in anuran amphibians. Surprisingly, despite the long history of anuran amphibians as model organisms for studying acoustic communication and physiology, we know very little about how variation in circulating hormone levels contributes to variation in the vocal quality of males. Proposed relationships between androgen levels and vocal quality depicted in recent models, for example, are subject to the same criticisms raised for similar models proposed in relation to birds, namely that the evidence for graded effects of androgens on vocal performance is often weak or not rigorously tested and responses seen in one species are often not observed in other species. Although several studies offer intriguing support for graded effects of hormones on calling behavior, additional comparative studies will be required to understand these relationships. Recent studies indicate that hormones may also mediate changes in anuran females' choice of mates, suggesting that the hormone levels of females can influence the evolution of males' mating signals. No studies to date have concurrently addressed the potential complexity of hormone-behavior relationships from the perspective of sender as well as receiver, nor have any studies addressed the costs that are potentially associated with changes in circulating hormone levels in anurans (i.e., life-history tradeoffs associated with elevations in circulating androgens in males). The mechanisms involved in hormonally induced changes in signal production and selectivity also require further investigation. Anuran amphibians are, in many ways, conducive to investigating such questions.     

Phylogeny and taxonomy of the Prenolepis genus‐group of ants (Hymenoptera: Formicidae)

Abstract. We investigated the phylogeny and taxonomy of the Prenolepis genus‐group, a clade of ants we define within the subfamily Formicinae comprising the genera Euprenolepis, Nylanderia, gen. rev. , Paraparatrechina, gen. rev. & stat. nov. , Paratrechina, Prenolepis and Pseudolasius. We inferred a phylogeny of the Prenolepis genus‐group using DNA sequence data from five genes (CAD, EF1αF1, EF1αF2, wingless and COI) sampled from 50 taxa. Based on the results of this phylogeny the taxonomy of the Prenolepis genus‐group was re‐examined. Paratrechina (broad sense) species segregated into three distinct, robust clades. Paratrechina longicornis represents a distinct lineage, a result consistent with morphological evidence; because this is the type species for the genus, Paratrechina is redefined as a monotypic genus. Two formerly synonymized subgenera, Nylanderia and Paraparatrechina, are raised to generic status in order to provide names for the other two clades. The majority of taxa formerly placed in Paratrechina, 133 species and subspecies, are transferred to Nylanderia, and 28 species and subspecies are transferred to Paraparatrechina. In addition, two species are transferred from Pseudolasius to Paraparatrechina and one species of Pseudolasius is transferred to Nylanderia. A morphological diagnosis for the worker caste of all six genera is provided, with a discussion of the morphological characters used to define each genus. Two genera, Prenolepis and Pseudolasius, were not recovered as monophyletic by the molecular data, and the implications of this result are discussed. A worker‐based key to the genera of the Prenolepis genus‐group is provided.