The wound response of the siphonous green algal genusCaulerpa III: Composition and origin of the wound plugs

Summary A complex, higly sulphated glucoxylomannogalactan has been extracted in a yield of about 1% dry weight fromC. simpliciuscula. This polysaccharide is similar in composition to sulphated polysaccharides previously isolated from otherCaulerpa species (Mackie andPercival, 1961). The most likely location of this compound in the unwounded cell is in the vacuole. This polysaccharide appears as the major component in wound plugs, forming a viscoelastic barrier between the protoplasm and the external environment. The properties of the sulphated polysaccharide were studied in an effort to understand the physiology and mechanism of wound plug formation.     

Heat-shock protein 72 cell-surface expression on human lung carcinoma cells is associated with an increased sensitivity to lysis mediated by adherent natural killer cells

 The cell-surface expression patterns of major histocompatibility complex (MHC) class I, class II and heat-shock protein 72 (HSP72) molecules were measured on human lung (LX-1) and mammary (MX-1) carcinoma cells. No major differences were found in the MHC cell-surface expression pattern of both cell lines. However, they differ significantly in their capacity to express HSP72 on their cell surface. Under physiological conditions LX-1 cells express HSP72 molecules on more than 90% of the cells, whereas MX-1 cells exhibit no significant HSP72 cell-surface expression (less than 5%). These expression patterns remained stable in all further cell passages tested. The sensitivity to lysis mediated by an interleukin-2 (IL-2)-stimulated, adherent natural killer (NK) cell population could be correlated with the amount of cell-surface-expressed HSP72 molecules. By antibody-blocking studies, using HSP72-specific monoclonal antibody (mAb), a strong inhibition of lysis was only found with LX-1 cells but not with MX-1 cells. In contrast to the cell-surface expression, the cytoplasmic amount of HSP72 in MX-1 cells was twice as high compared to LX-1 cells under physiological conditions. After nonlethal heat-shock the rate of induction and the total cytoplasmic amounts of HSP72 were comparable in both cell lines. The clonogenic cell viability of LX-1 cells after incubation at temperatures ranging from 41°C to 44°C was significantly elevated compared to that of MX-1 cells. In conclusion we state the following: (i) HSP72 cell-surface expression on human carcinoma cells is independent of the cytoplasmic amount of HSP72; (ii) the cell-surface expression of HSP72 is associated with an increased sensitivity of tumour cells to lysis mediated by an IL-2-stimulated, adherent NK cell population; (iii) thermoresistance is not related to the cytoplasmic HSP72 level but might be related to the amount of HSP72 expressed on the cell surface. Received: 20 June 1996 / Accepted: 25 September 1996     

Temperature Effect on the Photo-Accumulation and Phobic Response of Volvox aureus*

SYNOPSIS. The effect of temperature on photoaccumulation and photophobic response of Volvox aureus were studied. The algae exhibited positive photoaccumulation at room temperature and negative at low temperature. When stimulated with light of intermediate intensiy (～ 5 × 10³ lux), the phobic response of the algae consisted of a decrease in the frequency or the cessation of flagellar movement in the anterior cells. At room temperature, an increase in light intensity elicited the phobic response, whereas at low temperature a decrease in light intensity was the effective stimulus. The phobic response lasted only a few seconds. The positive and negative photoaccumulations of the algae could be explained by the brief cessation of flagellar movement in the anterior cells, elicited by an increase of stimulus light at room temperature or a decrease of stimulus at low temperature.     

Gut-associated immune effector responses in immunocompetent and immunocomprimised mice with Giardia lamblia

Abstract Significantly higher Giardia lamblia trophozoites load in the intestine of infected mice accompanied pronounced influx of suppressor/cytotoxic T cells (Lyt 2.2⁺), T cells (Thy 1.2⁺) and significant reduction in IgA-containing cells in the gut during the establishment and peak phases of infection. The induction of helper/inducer T cells (Lyt 1.1⁺) and significant enhancement of IgA-containing cells in gut resulted in the decline of the trophozoite loads. However, the prior treatment of animals with dexamethasone alone resulted in significant reduction in helper/inducer T cells (Lyt 1.1⁺) and the IgA-containing cells in the gut; the percents of suppressor/cytotoxic T cells (Lyt 2.2⁺) and IgM-containing cells remained unaltered. Although the G. lamblia infection in such animals further significantly increased the influx of suppressor/cytotoxic T cells, the late response of helper/inducer T cells and IgA-containing cells was abrogated during the decline phase of infection. The significant reduction in the trophozoite load — despite immuno-suppressive therapy — appeared to be due to unaltered IgM response in such animals which probably took over the function of IgA in defense against G. lamblia . The data of the investigation thus suggested a role of helper/inducer T cells and antibodies producing cells in gut as important effector cells resulting in the termination of primary G. lamblia infection.     

OsmiR167a‐targeted auxin response factors modulate tiller angle via fine‐tuning auxin distribution in rice

Rice tiller angle determines plant growth density and further contributes grain production. Although a few genes have been characterized to regulate tiller angle in rice, the molecular mechanism underlying the control of tiller angle via microRNA is poorly understood. Here, we report that rice tiller angle is controlled by OsmiR167a‐targeted auxin response factors OsARF12, OsARF17 and OsARF25. In the overexpression of OsMIR167a plants, the expression of OsARF12, OsARF17 and OsARF25 was severely repressed and displayed larger tiller angle as well as the osarf12/osarf17 and osarf12/ osarf25 plants. In addition, those plants showed compromised abnormal auxin distribution and less sensitive to gravity. We also demonstrate that OsARF12, OsARF17 and OsARF25 function redundantly and might be involved in HSFA2D and LAZY1‐dependent asymmetric auxin distribution pathway to control rice tiller angle. Our results reveal that OsmiR167a represses its targets, OsARF12, OsARF17 and OsARF25, to control rice tiller angle by fine‐tuning auxin asymmetric distribution in shoots.