Influence of Lernaeocera branchialis (Crustacea: Copepoda) on growth rate of Atlantic cod, Gadus morhua

Influence of Lernaeocera branchialis, a hematophagous copepod, on the growth rate of Atlantic cod, Gadus morhua, was investigated in fish of various sizes. Initially, it appeared that growth, over a 16-mo period, was reduced when single or multiple infections were present. We then examined growth rate by comparing food consumption, weight gain, food conversion efficiency, and condition (k) factor over a 2-mo period and subsequently over a 4 wk in control and experimentally infected fish. Total body weight and length of each fish, controls and infected were determined before and after feeding known weights of food. Adults infected with young parasites consumed more food and gained more weight than controls, especially in the first month, but food conversion efficiency and k-factor were greater than those of controls after 2 mo, but food efficiency was still lower than in controls. In 2 groups of young infected fish, all values were consistently lower than those of uninfected fish of comparable size during the 2-mo period. Three additional trials on immature cod confirmed that infected fish consumed less food and exhibited less growth than infected controls. Our results suggest that only adult cod infected with immature parasites compensate for the infections by increasing food consumption, thus resulting in a transitory weight gain. Additionally, parasites that have completed their reproductive activities still produce subtle effects in the form of low food conversion efficiency in their hosts.     

Art, Science, or Politics? The Crisis in Hunter-Gatherer Studies

In the complex history of hunter-gatherer studies, several overlapping and at times antagonistic discourses can be discerned. However, one critique has emerged that would render all hunter-gatherer discourses irrelevant and do away with the concept altogether. The paper explores the poststructuralist roots of this "revisionism" and then argues why the concept of hunter-gatherer continues to be politically relevant and empirically valid. However, if they are to fulfill their promise of illuminating an increasingly fragmented and alienating modernity, hunter-gatherer studies will have to become more attuned to issues of politics, history, context, and reflexivity.     

Cloning of two adult hamster globin cDNAs (alpha and beta major).

A cDNA library was prepared from poly(A) mRNA extracted from adult anemic hamster spleen erythroid cells. cDNA clones containing inserts coding for adult alpha and beta major globin chains were isolated. Their identity was confirmed by (a) translation of hybrid selected mRNA and (b) nucleotide sequence analysis of the inserts and comparison to the adult globin cDNAs of mouse, rabbit and human. Availability of sequences for embryonic (Li et al. (1992) Biochim. Biophys. Acta 1130, 218-220) and adult globin cDNAs (this report) will aid in investigations of the molecular mechanisms involved in the globin ontogeny of hamsters.     

Nutritional regulation of late meiotic events in Saccharomyces cerevisiae through a pathway distinct from initiation.

The IME1 gene is essential for initiation of meiosis in the yeast Saccharomyces cerevisiae, although it is not required for growth. Here we report that in stationary-phase cultures containing low concentration of glucose, cells overexpressing IME1 undergo the early meiotic events, including DNA replication, commitment to recombination, and synaptonemal complex formation and dissolution. In contrast, later meiotic events, such as chromosome segregation, commitment to meiosis, and spore formation, do not occur. Thus, nutrients can repress the late stages of meiosis independently of their block of initiation. Cells arrested at this midpoint in meiosis are relatively stable and can resume meiotic differentiation if transferred to sporulation conditions. Resumption of meiosis does not require repression of IME1 expression, since IME1 RNA levels stay high after transfer of the arrested cells to sporulation medium. These results suggest that meiosis in S. cerevisiae is a paradigm of a differentiation pathway regulated by signal transduction at both early and late stages.     

C-terminal polypeptides are necessary and sufficient for in vivo targeting of transiently-expressed proteins to peroxisomes in suspension-cultured plant cells

Summary The potential of tobacco BY-2 suspension-cultured cells for examining in vivo targeting and import of proteins into plant peroxisomes was shown recently in our laboratory. In the current study, the necessity and sufficiency of putative C-terminal targeting signals on cottonseed malate synthase and bacterial chloramphenicol acetyl-transferase (CAT) were examined in BY-2 cells. Cotton suspension cells also were evaluated as another in vivo peroxisome targeting system. Ultrastructural views of BY-2 cells showed that the peroxisomes were relatively small (0.1-0.3 m diameter), a characteristic of so-called unspecialized peroxisomes, Peroxisomes in cotton and tobacco cells were identified with anti-cottonseed catalase IgGs as distinct immunofluorescent particles clearly distinguishable from abundant immunofluorescent mitochondria and plastids, marked with antibodies to -ATPase and stearoyl-ACP 9 desaturase, respectively. The C-terminal ser-lys-leu (SKL) motif is a well-established peroxisome targeting signal (PTS 1) for mammals and yeasts, but not for plants. Antiserum raised against SKL peptides recognized proteins only in peroxisomes in cotton and tobacco cells. The necessity of SKL-COOH for targeting of proteins to plant peroxisomes had not been demonstrated; we showed that SKL-COOH was necessary for directing cottonseed malate synthase to BY-2 peroxisomes. KSRM-COOH, a conservative modification of SKL-COOH, was shown by others to be sufficient for redirecting CAT in stably-transformed Arabidopsis plants to the leaf peroxisomes. Here we show with the same CAT constructs (e.g., pMON316CAT-KSRM) that KSRM is sufficient for targeting transiently-expressed passenger proteins to unspecialized BY-2 peroxisomes. These results provide new direct evidence for the necessity of SKL-COOH (a type 1 PTS) and sufficiency of a conservative modification of the PTS 1 (KSRM-COOH) for in vivo, heterologous targeting of proteins to plant peroxisomes.Abbreviations CAT chloramphenicol acetyltransferase - CHO cells Chinese hamster ovary cells - DAB 3,3-diaminobenzidine - GUS -glucuronidase - ICL isocitrate lyase - KSRM lysine-serine-arginine-methionine - MS malate synthase - PBS phosphate-buffered saline - PTS peroxisome targeting signal - SKL serine-lysine-leucine - tobacco BY-2 Bright Yellow-2 Dedicated to Professor Eldon H. Newcomb in recognition of his contributions to cell biology     

Age,Experience, and the Response of Streamside Salamander Hatchlings to Chemical Cues from Predatory Sunfish

Previous work has shown that streamside salamander larvae (Ambystoma barbouri; Ambystomatidae) exhibit an adaptive ‘sink to the bottom’ response to chemical cues from predatory green sunfish (Lepomis cyanellus; Centrarchidae), that is, larvae sink to the bottom more quickly (thus minimizing exposure time to sunfish predation) when they are dropped into water with sunfish chemicals (as compared to Ashless controls). Here, we examined this anti-predator behaviour in early hatchlings and the effects of age and experience on subsequent expression of this behaviour. Hatchlings responded significantly to fish chemical cues within the first 18 h after hatching. Age did not significantly influence this response, i.e. regardless of age (1, 7, or 14 days after hatching) larvae showed a significant response during their first exposure to fish chemical cues. Experience also did not significantly influence the larval response to fish chemicals i.e., repeated exposures over 2 weeks did not significantly influence the magnitude of the response. Finally, comparisons of 3 siblingships detected significant variation among siblingships that might reflect genetic variation in this behaviour.     

A linkage map of diploid Avena based on RFLP loci and a locus conferring resistance to nine isolates of Puccinia coronata var. ‘avenae’

An F₂ oat population was produced by crossing the diploid (n=7) species Avena strigosa (CI 3815) with A. wiestii (CI 1994), resistant and susceptible, respectively, to 40 isolates of Puccinia coronata, the causal agent of crown rust. Eighty-eight F₂ individuals were used to construct an RFLP linkage map representing the A genome of cultivated hexaploid oat. Two hundred and eight RFLP loci have been placed into 10 linkage groups. This map covers 2416 cM, with an average of 12 cM between RFLP loci. Eighty-eight F₃ lines, derived from F₂ individuals used to construct the map, were screened for resistance to 9 isolates of P. coronata. One locus, Pca, was found to confer a dominant resistance phenotype to isolates 203, 258, 263, 264B, 290, 298, 325A, and 345. Pca also conferred resistance to isolate 276; however, an unlinked second gene may also be involved.Journal Paper No. 15143 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 3134 and 2447     

Inhibition of Immune Complex-Induced Inflammation by A small Molecular Weight Selectin Antagonist

The anti-inflammatory effect of a small molecular weight antagonist of P- and E-selectin-dependent cell adhesion was examined. The glycolipid sulphatide was shown to block the adherence of thrombin-activated rat platelets to HL-60 cells. This interaction is known to be dependent on P-selectin. The rat dermal reverse passive Arthus reaction was used to assess the effect of sulphatide on a neutrophil dependent inflammatory response. Sulphatide dosedependently blocked both the vascular permeability increase and cell infiltration after intraperitoneal administration. These results show that a small molecular weight compound which blocks P- and E-selectin dependent adhesion in vitro can effectively block the inflammation due to immune complex deposition. A compound with this type of profile may have therapeutic potential in the treatment of immune complex mediated diseases.