Working with living krill – the people and the places

The fascination of Antarctic scientists with Antarctic krill and their capabilities has a long and varied history, and prompted many scientists to maintain and manipulate krill under laboratory conditions. Starting in the Discovery era with Mackintosh at the King Edward Point labs on South Georgia, 1930, scientists have collected krill from sailing vessels, small boats, inflatable zodiacs and large ice-breaking vessels. Krill have been maintained in small and large jars, deep rectangular tanks, large round tanks and in flow-through and recycling systems. They have been maintained both on board research vessels and in laboratories, in flowing seawater systems at ambient conditions and in temperature-controlled environmental rooms. A few researchers have transported living krill back to their home laboratories, for example tropical laboratories in Japan (Murano) and Australia (Ikeda), temperate laboratories (Nicol) in Australia, a northern European laboratory in Germany (Marschall) and a sunny maritime laboratory in California (Ross and Quetin). The goals have been varied: short-term experiments to understand in situ physiological rates, long-term experiments to test the effects of manipulations or controlled changes in environmental conditions, and behavioral responses. We take you on a brief historical tour as we trace the lineage of modern day research on living Antarctic krill.     

Suppression of apoptosis induced by growth factor withdrawal by an oncogenic form of c-Cbl

The v-Cbl oncogene induces myeloid and B-cell leukemia; however, the mechanism by which transformation occurs is not understood. An oncogenic form of c-Cbl (Cbl-DeltaY371) was expressed in the interleukin-3 (IL-3)-dependent cell line 32Dcl3 to determine whether it was able to induce growth factor-independent proliferation. We were unable to isolate clones of transfected 32Dcl3 cells expressing Cbl-DeltaY371 that proliferated in the absence of IL-3. In contrast, 32Dcl3/Cbl-DeltaY371 cells did not undergo apoptosis like parental 32Dcl3 cells when cultured in the absence of IL-3. Both 32Dcl3 and 32D/CblDeltaY371 cells arrested in G(1) when cultured in the absence of IL-3. Approximately 18% of the 32Dcl3 cells cultured in the absence of IL-3 for 24 h were present in a sub-G(1) fraction, while only 4% of the 32D/Cbl-DeltaY371 and 2% of the 32D/Bcl-2 cells were found in a sub-G(1) fraction. There was no difference in the pattern of tyrosine-phosphorylated proteins observed following stimulation of either cell type with IL-3. The phosphorylation of JAK2, STAT5, and endogenous c-Cbl was identical in both cell types. No differences were detected in the activation of Akt, ERK1, or ERK2 in unstimulated or IL-3-stimulated 32D/Cbl-DeltaY371 cells compared with parental 32Dcl3 cells. Likewise, there was no difference in the pattern of phosphorylation of JAK2, STAT5, ERK1, ERK2, or Akt when 32Dcl3 and 32D/CblDY371 cells were withdrawn from medium containing IL-3. The protein levels of various Bcl-2 family members were examined in cells grown in the absence or presence of IL-3. We observed a consistent increased amount of Bcl-2 protein in five different clones of 32D/Cbl-DeltaY317 cells. These data suggest that the Cbl-DeltaY371 mutant may suppress apoptosis by a mechanism that involves the overexpression of Bcl-2. Consistent with this result, activation of caspase-3 was suppressed in 32D/Cbl-DeltaY371 cells cultured in the absence of IL-3 compared with 32Dcl3 cells cultured under the same conditions.     

Functional rice centromeres are marked by a satellite repeat and a centromere-specific retrotransposon

The centromere of eukaryotic chromosomes is essential for the faithful segregation and inheritance of genetic information. In the majority of eukaryotic species, centromeres are associated with highly repetitive DNA, and as a consequence, the boundary for a functional centromere is difficult to define. In this study, we demonstrate that the centers of rice centromeres are occupied by a 155-bp satellite repeat, CentO, and a centromere-specific retrotransposon, CRR. The CentO satellite is located within the chromosomal regions to which the spindle fibers attach. CentO is quantitatively variable among the 12 rice centromeres, ranging from 65 kb to 2 Mb, and is interrupted irregularly by CRR elements. The break points of 14 rice centromere misdivision events were mapped to the middle of the CentO arrays, suggesting that the CentO satellite is located within the functional domain of rice centromeres. Our results demonstrate that the CentO satellite may be a key DNA element for rice centromere function.     

Changes in LPLa and reverse cholesterol transport variables during 24-h postexercise period

We investigated the time course of exercise-induced lipoprotein lipase activity (LPLa) and reverse cholesterol transport (RCT) during the 24-h postexercise period. Subjects were 10 sedentary normolipidemic males [NTG; fasting triglyceride (TG) = 89.1 +/- 8.6 mg/dl] and 6 hyperlipidemic males (HTG; fasting TG = 296.8 +/- 64.0 mg/dl). Each subject performed a control trial (no exercise) and 4 exercise trials. In the exercise trials, a subject jogged on a treadmill at 60% of his maximal O(2) consumption for 1 h. Pre- and postheparin blood samples were taken before exercise (baseline) and at 4, 8, 12, and 24 h after exercise. There was no group difference in LPLa (P > 0.05) over the time points. When the LPLa data from the two groups were combined, LPLa at 24 h after exercise was higher than baseline or at 4, 8, 12 h after exercise (P < 0.05). Plasma TG and lecithin-cholesterol acyltransferase activity (LCATa) were higher in HTG than in NTG, and the total high-density lipoprotein-cholesterol (HDL(tot)-Chol) was lower in HTG than in NTG (P < 0.05). HDL(2)-Chol, LCATa, and cholesterol ester transfer protein activity did not differ during the 24-h postexercise period (P > 0.05). These results suggest that LPLa is still increasing 24 h after an acute aerobic exercise and that the magnitude of the increase in exercise-induced LPLa in HTG was similar to that in NTG. Furthermore, in the sedentary population with or without HTG, the variables related to RCT do not change during the 24-h period after exercise.     

Rapid microtubule-dependent induction of neurite-like extensions in NIH 3T3 fibroblasts by inhibition of ROCK and Cbl

A number of key cellular functions, such as morphological differentiation and cell motility, are closely associated with changes in cytoskeletal dynamics. Many of the principal signaling components involved in actin cytoskeletal dynamics have been identified, and these have been shown to be critically involved in cell motility. In contrast, signaling to microtubules remains relatively uncharacterized, and the importance of signaling pathways in modulation of microtubule dynamics has so far not been established clearly. We report here that the Rho-effector ROCK and the multiadaptor proto-oncoprotein Cbl can profoundly affect the microtubule cytoskeleton. Simultaneous inhibition of these two signaling molecules induces a dramatic rearrangement of the microtubule cytoskeleton into microtubule bundles. The formation of these microtubule bundles, which does not involve signaling by Rac, Cdc42, Crk, phosphatidylinositol 3-kinase, and Abl, is sufficient to induce distinct neurite-like extensions in NIH 3T3 fibroblasts, even in the absence of microfilaments. This novel microtubule-dependent function that promotes neurite-like extensions is not dependent on net changes in microtubule polymerization or stabilization, but rather involves selective elongation and reorganization of microtubules into long bundles.     

Physiological role of neuropeptide Y in the regulation of the ascending phase of the peristaltic reflex

The physiological role of neuropeptide Y (NPY) and of specific NPY receptors in regulating the intestinal peristaltic reflex was examined in three-compartment flat-sheet preparations of rat colon. Graded muscle stretch or mucosal stimulation applied to the central compartment inhibited NPY release in the orad compartment where ascending contraction was measured. NPY and the Y1-receptor agonist [Leu31, Pro34]NPY inhibited, whereas the selective Y1-receptor antagonist BIBP 3226 augmented ascending contraction and substance P (SP) release in the orad compartment induced by muscle stretch or mucosal stimulation. Neither agonist nor antagonist had any effect on descending relaxation or VIP release in the caudad compartment. The Y2-receptor agonist NPY13-36 and antagonist BIIE 0246 had no effect on peptide release or mechanical response. The results indicate that suppression of a tonic inhibitory influence of NPY neurons on excitatory neurotransmitter release contributes substantially to the orad contractile phase of the peristaltic reflex. The effect of NPY on neurotransmitter release is mediated by Y1 receptors.     

De novo evolution of satellite DNA on the rye B chromosome

The most distinctive region of the rye B chromosome is a subtelomeric domain that contains an exceptional concentration of B-chromosome-specific sequences. At metaphase this domain appears to be the physical counterpart of the subtelomeric heterochromatic regions present on standard rye chromosomes, but its conformation at interphase is less condensed. In this report we show that the two sequence families that have been previously found to make up the bulk of the domain have been assembled from fragments of a variety of sequence elements, giving rise to their ostensibly foreign origin. A single mechanism, probably based on synthesis-dependent strand annealing (SDSA), is responsible for their assembly. We provide evidence for sequential evolution of one family on the B chromosome itself. The extent of these rearrangements and the complexity of the higher-order organization of the B-chromosome-specific families indicate that instability is a property of the domain itself, rather than of any single sequence. Indirect evidence suggests that particular fragments may have been selected to confer different properties on the domain and that rearrangements are frequently selected for their effect on DNA structure. The current organization appears to represent a transient stage in the evolution of a conventional heterochromatic region from complex sequences.     

Retrotransposon evolution in diverse plant genomes

Retrotransposon or retrotransposon-like sequences have been reported to be conserved components of cereal centromeres. Here we show that the published sequences are derived from a single conventional Ty3-gypsy family or a nonautonomous derivative. Both autonomous and nonautonomous elements are likely to have colonized Poaceae centromeres at the time of a common ancestor but have been maintained since by active retrotransposition. The retrotransposon family is also present at a lower copy number in the Arabidopsis genome, where it shows less pronounced localization. The history of the family in the two types of genome provides an interesting contrast between "boom and bust" and persistent evolutionary patterns.