Influence of intracellular and extracellular tonicities on water permeability in Characean cells

Summary The effect of the concentration of the central vacuolar sap on water permeability previously demonstrated onNitella internode (Tazawa and Kamiya 1966), has been further studied. By using a technique of vacuole perfusion the ionic concentration of the cell sap has been modified independently of its tonicity. Transcellular water permeability has been measured by means of a double-chamber osmometer.When the tonicities of artificial saps were adjusted to that of the natural cell sap, wide variations in the concentration of K⁺, Na⁺, or Ca⁺⁺ in the vacuole did not bring about any change in the magnitude of water permeability. On the other hand, water permeability was strongly influenced by varying the tonicity of the vacuolar medium by addition of mannitol. It increased when the tonicity was lowered from the normal level, while it decreased when tonicity was heightened. Water permeability was also decreased by increase in the tonicity of the external medium.Analysis of the results showed that the specific resistance to water flow across the plasmalemma and the tonoplast in series (the reciprocal of the water permeability k_p) was related to the osmotic pressures of the intracellular ( _i) and the extracellular ( ₀) medium by the empirical formula, l/k_p=0.088 + 0.015 . + 0.0074 ₀. Thus, intra- and extracellular tonicities influence the water permeability of theNitella internode independently of each other. The decrease in water permeability by increase in tonicity of the intra- or extracellular medium may be explained in terms of the effect of these tonicities on hydration of the cell membranes.The water permeability ofLamprothamnium, a brackish water Characeae was only one fourth that ofNitella, a fresh water Characeae. The lower permeability inLamprothamnium may be accounted for in terms of the high tonicities of its cell sap and external medium.     

Colony-stimulating factors and cytokine receptor network.

Cytokines play a vital role in coordinating immune and inflammatory responses. As many cytokine gene hunters have begun to focus their efforts on receptors, novel aspects of hemopoietic growth factor receptors have emerged. Two types of growth factor receptors have been classified--the cytokine receptor family and growth factor receptor family with tyrosine kinase activity. The two types of receptors may have unique roles in 'inducible' and 'constitutive' hemopoiesis which are controlled by immunological stimuli and by interaction with stromal cells, respectively.     

Glucocorticoids suppress and oestrogens enhance the lipopolysaccharide-induced increase in putrescine and N1-acetylspermidine in mouse liver

Previously we reported that administration of lipopolysaccharide (LPS) to mice increased the hepatic levels of putrescine (PUT) and N¹-acetylspermidine (N¹-acetyl-SPD). In the current study, we examined the in vivo effects of some steroid hormones on the LPS-induced increase in PUT and N¹-acetyl-SPD. Corticosterone, hydrocortisone and dexamethasone suppressed the LPS-induced increase in PUT and N¹-acetyl-SPD in mouse liver in a dose-dependent manner, dexamethasone being the most effective among them. On the other hand, oesterone and oestradiol-17β enhanced the LPS-induced increase in PUT and N¹-acetyl-SPD in a dose-dependent manner. Oestradiol-17 and 16β-ethyl-oestradiol, as an inactive oestradiol isomer and an antioestrogen, respectively, likewise enhanced the increase in PUT and N¹-acetyl-SPD concentrations induced by LPS. 16-hydroxy-oestradiol (oestriol), 16-hydroxyestrone, 2-hydroxyoestradiol, 2-hydroxyoestrone, progesterone, testosterone, diethylstilboestrol and nonsteroidal antioestrogen such as tamoxifen and nafoxidine had no effect on the increase. Oestradiol-17β enhanced and corticosterone had little on the carbon tetrachloride-induced increase in PUT and N¹-acetyl-SPD. These results suggest that glucocorticoids suppress the increase by preventing the immunological injury by Kupffer cells on hepatocytes and that the stimulatory effect of oestrogens may not be associated with their oestrogenic activities mediated by the oestrogen receptor system.     

Increase in the glucosylated form of erythrocyte Cu-Zn-superoxide dismutase in diabetes and close association of the nonenzymatic glucosylation with the enzyme activity

Human erythrocytes contain glucosylated and nonglucosylated Cu-Zn-superoxide dismutases which can be separated by boronate affinity chromatography. The percentage of the glucosylated form is significantly increased in the erythrocytes of patients with diabetes as compared to normal erythrocytes. The nonglucosylated form of Cu-Zn-superoxide dismutase, which was washed through the boronate column, was glucosylated in vitro upon exposure to radioactive or non-radioactive D-glucose. Incorporation of D-glucose into the protein was observed, and with the increase in glucosylation, the enzymatic activity decreased, indicating that the glucosylation of the enzyme led to a low active form. This is the first demonstration that superoxide dismutase is glucosylated in erythrocytes and that the glucosylation leads to the inactivation of the enzyme.     

Localization in situ of c-myc mRNA and c-myc protein in adult mouse testis

Summary It has been suggested that c-myc, one of the proto-oncogenes, plays a role in normal somatic cell proliferation and differentiation. To define whether c-myc is only expressed during somatic cell division or is also expressed during meiotic cell division, the production of c-myc mRNA and protein were investigated in the mouse testis by usingin situ hybridization with non-radioactive DNA probes and enzyme immunohistochemistry respectively. Forin situ hybridization, T-T dimerized DNA probes were used and DNAs hybridizedin situ were detected immunohistochemically using specific antibody against T-T dimer. The results indicate that c-myc mRNA and protein are expressed in a cell-cycle-dependent manner only in spermatogonia and not in spermatocytes and spermatids.