Adverse effects of tempol on hidrosaline balance in rats with acute sodium overload

We studied the effects of tempol, an oxygen radical scavenger, on hydrosaline balance in rats with acute sodium overload. Male rats with free access to water were injected with isotonic (control group) or hypertonic saline solution (0.80 mol/l NaCl) either alone (Na group) or with tempol (Na-T group). Hydrosaline balance was determined during a 90 min experimental period. Protein expressions of aquaporin 1 (AQP1), aquaporin 2 (AQP2), angiotensin II (Ang II) and endothelial nitric oxide synthase (eNOS) were measured in renal tissue. Water intake, creatinine clearance, diuresis and natriuresis increased in the Na group. Under conditions of sodium overload, tempol increased plasma sodium and protein levels and increased diuresis, natriuresis and sodium excretion. Tempol also decreased water intake without affecting creatinine clearance. AQP1 and eNOS were increased and Ang II decreased in the renal cortex of the Na group, whereas AQP2 was increased in the renal medulla. Nonglycosylated AQP1 and eNOS were increased further in the renal cortex of the Na-T group, whereas AQP2 was decreased in the renal medulla and was localized mainly in the cell membrane. Moreover, p47-phox immunostaining was increased in the hypothalamus of Na group, and this increase was prevented by tempol. Our findings suggest that tempol causes hypernatremia after acute sodium overload by inhibiting the thirst mechanism and facilitating diuresis, despite increasing renal eNOS expression and natriuresis.     

Determination of the Rate of CO(2) Evolution by Green Leaves in Light

The rate of CO₂ evolution in light by green leaves was determined by 2 methods in a closed system of gas analysis and by measuring the amount of CO₂ evolved into a CO₂ free air stream in an open system. All methods gave similar results under comparable conditions.     

Effects of Temperature on Photosynthesis and CO(2) Evolution in Light and Darkness by Green Leaves

Using an open and a closed system of gas analysis, it was found that CO₂ evolution in light and in darkness from plant leaves (sunflower, soybean, watermelon, eggplant, and jackbean) have a different response to temperature. While the rate of CO₂ evolution in light increased with increasing temperature from 17 to 35° and then declined, the rate of CO₂ evolution in darkness increased continuously up to 40°. The rate of CO₂ evolution in light was affected by light intensity. At 1800 ft-c and below 35° the rate of CO₂ evolution in light was greater than in darkness, but above 35° it became lower than in darkness. The Q₁₀ for CO₂ evolution in light was consistently lower than that in darkness.     

Expression and characterization of an active and thermally more stable recombinant antifreeze polypeptide from ocean pout, Macrozoarces americanus, in Escherichia coli: improved expression by the modification of the secondary structure of the mRNA.

The cDNA clone coding for the ocean pout antifreeze polypeptide (AFP) was modified to improve translation of its mRNA in Escherichia coli. A recombinant AFP (rAFP), MetLys-AFP-Lys, was expressed successfully using the lambda PL promoter, and constituted 1-2% of total bacterial proteins. The rAFP was purified to homogeneity from the soluble fractions of bacterial extracts. Its identity was confirmed by amino acid analysis, automated Edman degradation, immuno-blot and activity measurements. Although the rAFP is indistinguishable from the authentic AFP in its secondary structure, thermal hysteretic activity and the alteration of ice crystal structure, it is, however, thermally more stable (approximately 4.5 degrees C increase in Tm) and is more effective in inhibiting ice growth along the a-axis. These investigations indicate that the extra amino acids in rAFP significantly improve the thermal stability and ice-binding activity of the polypeptide.     

Ethylene production by young Aranda orchid flowers and buds

A high rate of ethylene production was observed in buds and young flowers of Aranda orchid, which increased with bud growth, reaching a high value in half-opened flower. This was followed by a gradual decline but it increased again when the flowers showed sign of senescence. Aminooxylacetic acid (AOA) inhibited ethylene production and bud expansion of Aranda buds.     

Interchain and intrachain disulphide bonds in human platelet glycoprotein IIb. Localization of the epitopes for several monoclonal antibodies.

The single interchain disulphide bond in platelet glycoprotein IIb (GPIIb) is accessible to extracellular reductants, and selective cleavage does not liberate GPIIb alpha from platelet plasma membrane, confirming that non-covalent interactions contribute to maintaining attachment of this subunit to the membrane. Eosin-maleimide labelling of isolated GPIIb after selective cleavage of this interchain disulphide bond, followed by full reduction and alkylation, CNBr cleavage, and analysis of the cleavage products allowed us to establish that this interchain disulphide bridge is formed between GPIIb beta (GPIIb beta-subunit) Cys-9 and GPIIb alpha Cys-826, and this conclusion was confirmed by independent routes. The other two cysteines of GPIIb beta (Cys-14 and Cys-19) form the single intrachain disulphide bond in this subunit. Last, the intrachain disulphides in GPIIb alpha (GPIIb alpha-subunit) are distributed in four main peptide domains which are not disulphide-bonded among themselves. The linear epitope for monoclonal antibody M1 is localized between Pro-4 and Met-24 (or Met-31) of GPIIb beta. The linear epitope for M3 is situated between Cys-826 and the C-terminus of GPIIb alpha. The M4 epitope is also linear and localized somewhere between residues 115 and 285 of GPIIb alpha. Finally, the epitopes for M5 and M6 are somewhere between Cys-608 and Met-704, within a 35 kDa membrane-bound chymotryptic product of digestion of GPIIb in whole platelets. The N-terminal amino acid sequences determined for eight different cleavage products of GPIIb alpha and GPIIb beta agree with the corresponding amino acid sequences predicted by cDNA sequence for human-erythroleukaemic-cell GPIIb [Poncz, Eisman, Heindenreich, Silver, Vilaire, Surrey, Schwartz & Bennett (1987) J. Biol. Chem. 262, 8476-8482].     

The study of the process of fluid-phase endocytosis in cervical squamous cells using fluorescent microspheres

Physiological processes in cervical squamous epithelium have not been extensively studied. Perhaps understandably, most of the research has concentrated on the pathology of the cervix, in particular dysplasia and malignancy. Fluid-phase endocytosis is a physiological process which has been demonstrated to be important in understanding disease development at other squamous epithelial sites, e.g. oesophagus. In this study, we have demonstrated by a new methodology developed in our laboratory using fluorescent microspheres and flow cytometry that fluid-phase endocytosis occurs in cervical squamous cells. The process has been shown to be dose- and time-dependent. This novel approach provides a means to improve our understanding of the physiological functions of the cervix and may provide insight into the pathogenesis of cervical neoplastic and non-neoplastic disease.     

Sporogenesis in Eusporangiate Ferns: I. Monoplastidic Meiosis in Angiopteris (Marattiales)

Angiopteris (Marattiales) undergoes the more primitive form of monoplastidic meiosis, while other ferns have evolved the polyplastidic type typical of seed plants. In monoplastidic cell division, the single plastid divides and serves as site of the microtubule organizing center (MTOC) for spindle formation resulting in coordinated division of plastid, nucleus, and cytoplasm. In plants with polyplastidic cell division, the MTOC is diffuse and generally perinuclear. Monoplastidic cell division is seen as a plesiomorphic feature that was inherited from algal ancestors containing a single plastid and modified through evolution. Monoplastidic meiosis occurs in all groups of bryophytes (although in only a few hepatics), Isoetes, Selaginella, certain generic segregates of Lycopodium, and in members of the Marattiales. It is not known to occur in psilophytes, Equisetum, leptosporangiate ferns, or seed plants. Received 30 January 2001/ Accepted in revised form 24 April 2001