Oxytocin mediates the acquisition of filial, odor-guided huddling for maternally-associated odor in preweanling rats

The present study was designed to examine possible roles of oxytocin (OT) in the acquisition of a filial huddling preference in preweanling rats. We used a procedure in which a scented, foster mother can induce an odor-guided huddling preference in preweanling pups, following a single, 2-h-long co-habitation ( [Kojima and Alberts, 2009] and Kojima and Alberts, 2011). This single, discrete period for preference learning enables us to observe the mother–pup interactions that establish the pups' preferences and to intervene with experimental manipulations. Four, 14-day-old littermates interacted with a scented foster mother that provided maternal care during a 2-h session. Two of the pups were pretreated with an intracerebroventricular injection of OT or an oxytocin antagonist (OTA), and the others received a vehicle injection. Filial preference for a maternally-paired odor was measured in a huddling test the next day. OT is necessary for acquisition of the filial preference: The preference learning was blocked in the pups treated with OTA, but not in their vehicle-treated littermates who experienced the same mother at the same time. Injection with exogenous OT did not augment the pups' preference. Manipulating pups' central OT also altered the contact interactions of the mother and pups. When some pups received OT, mother–litter aggregations formed as frequently and with similar combinations of bodies, but contact aggregations were significantly more cohesive than when some pups in the litter received OTA. We discuss dual, behavioral and neuroendocrine roles of OT in social learning by preweanling rats.     

Conversion of mono-polar to peritrichous flagellation in Vibrio alginolyticus

Precise regulation of the number and positioning of flagella are critical in order for the mono-polar-flagellated bacterium Vibrio alginolyticus to swim efficiently. It has been shown that, in V. alginolyticus cells, the putative GTPase FlhF determines the polar location and production of flagella, while the putative ATPase FlhG interacts with FlhF, preventing it from localizing at the pole, and thus negatively regulating the flagellar number. In fact, no ΔflhF cells have flagella, while a very small fraction of ΔflhFG cells possess peritrichous flagella. In this study, the mutants that suppress inhibition of the swarming ability of ΔflhFG cells were isolated. The mutation induced an increase in the flagellar number and, furthermore, most Vibrio cells appeared to have peritrichous flagella. The sequence of the flagella related genes was successfully determined, however, the location of the suppressor mutation could not been found. When the flhF gene was introduced into the suppressor mutant, multiple polar flagella were generated in addition to peritrichous flagella. On the other hand, introduction of the flhG gene resulted in the loss of most flagella. These results suggest that the role of FlhF is bypassed through a suppressor mutation which is not related to the flagellar genes.     

Recognition of mitochondrial protein precursor lacking arginine at position -2 by mitochondrial processing peptidase: processing of bovine cytochrome P450(SCC) precursor

Mitochondrial processing peptidase (MPP) specifically cleaves off the N-terminal presequence of the mitochondrial protein precursor. Previous studies demonstrated that Arg at position -2 from the cleavage site, which is found among many precursors, plays a critical role in recognition by MPP. We analyzed the structural elements of bovine cytochrome P450 side-chain cleavage enzyme precursor [pre-P450(SCC)], which has Ala at position -2, for recognition by MPP. Replacement of Ala position -2 of pre-P450(SCC) with Arg resulted in an increase in the cleavage rate. Replacement with Gly caused a reduction in the cleavage rate and the appearance of an additional cleavage site downstream of the authentic site. A pre-P450(SCC) mutant with Met at position -2 retained cleavage efficiency equal to that of the wild type. These results indicate that -2 Ala of pre-P450(SCC) is recognized by MPP as a determinant for precise cleavage, and that the amino acid at -2 is required to have a straight methylene chain for interaction with the S(2) site. The preference for distal basic residues, a hydrophobic residue at +1, and hydroxyl residues at +2 and +3, was almost the same as those of the precursors with Arg at -2, indicating that the recognition mechanism of pre-P450(SCC) by MPP is essentially the same as that of the precursors with Arg at position -2.     

Heterogeneity in response to interleukin 2 and interleukin 2-producing ability of adult T cell leukemic cells

To examine the possibility of heterogeneous mechanisms in the proliferation of adult T cell leukemia (ATL) cells, leukemic cells from 13 patients, nine acute-type and four chronic-type ATL, were examined for the production of interleukin 2 (IL 2) with or without mitogenic stimulation and their response to recombinant IL 2 when exogeneously added. The leukemic cells were classified into four groups, as follows. Group 1 (two patients): Cells of this group produced IL 2 messenger RNA, secreted IL 2, and proliferated when cultured in mitogen-free medium. The spontaneous proliferation of the cells in mitogen-free medium was inhibited by anti-Tac/IL 2 receptor and anti-IL 2 monoclonal antibodies. Moreover, the thymidine incorporation by the cells was enhanced in response to exogeneously added recombinant IL 2 and IL 2 produced by themselves. These results indicate that the ATL cells of this group proliferate with autostimulation by IL 2. Group 2 (seven patients): Cells of this group did not secrete IL 2 when cultured in mitogen-free medium, but the cells showed response to exogeneously added recombinant IL 2 and proliferated in culture. These results indicate that the ATL cells of this group proliferate by a paracrine mechanism. Group 3 (one patient): Cells of this group secreted IL 2 in mitogen-free medium. However, the spontaneous proliferation of these cells in vitro was very low, and the response to recombinant IL 2 was also very low. Group 4 (three patients): Cells of this group did not secrete IL 2 in mitogen-free medium. Spontaneous proliferation and the response to recombinant IL 2 were also very low. The clinical feature of all patients of Groups 1 and 2 was acute-type, and that of Groups 3 and 4 was chronic-type. Thus, we conclude that heterogeneous mechanisms exist in the proliferation of leukemic cells, and that growth rate in mitogen-free medium and response to IL 2 of the cells may have a significant relationship to the clinical feature, acute- or chronic-type.