4-Deoxy-4-fluoro-D-mannose inhibits the glycosylation of the G protein of vesicular stomatitis virus

The effect of 4-deoxy-4-fluoro-D-mannose (4F-Man), a synthetic analog of D-mannose, on the synthesis of the glycoprotein (G) of vesicular stomatitis virus was examined. Nearly confluent monolayers of cultured BHK21 cells infected with vesicular stomatitis virus were incubated for 2 h with 4F-Man (0-10 mM) or for 1 h with tunicamycin (2 micrograms/ml) and then pulse-labeled with [35S]methionine or [3H]glucosamine. After a 90-min chase period, the cells were lysed and the viral proteins were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography. The 35S-labeled G protein from cells exposed to greater than or equal to 1 mM 4F-Man migrated more rapidly than G protein isolated from control cells and with the same electrophoretic mobility as the glycoprotein produced by cells treated with tunicamycin. When infected cells were labeled with [3H]glucosamine, little or no radioactivity was associated with G protein synthesized in the presence of greater than or equal to 1 mM 4F-Man. The conclusion that 4F-Man blocks the glycosylation of the G protein was supported by experiments which demonstrated that the fluorosugar inhibits the synthesis of lipid-linked oligosaccharides.     

Production of auto-anti-idiotypic antibody during the normal immune response: IX. Characteristics of the auto-anti-idiotype antibody and its production

Using hapten-reversible inhibition of plaque formation as an assay for auto-anti-idiotype antibody (anti-Id) and as a means for following idiotype (Id) expression, we have obtained evidence that following immunization with trinitrophenyl (TNP) conjugates (a) there are differences in Id expression in the anti-TNP antibody response to different TNP conjugates although there is some overlap; (b) different strains, although showing some differences in Id expression, tend to produce cross-reactive Ids, thus no obvious allotype linked inheritance of Id expression is observed in this heterogeneous immune response; (c) the auto-anti-Id produced following immunization with TNP-Brucella abortus or TNP-Ficoll tends to be of the IgG_2a and IgG_2b isotypes.     

Temporal patterns of protein phosphorylation after angiotensin II, A23187 and/or 12-O-tetradecanoylphorbol 13-acetate in adrenal glomerulosa cells.

The temporal patterns of protein phosphorylation in the adrenal glomerulosa cell were analysed by two-dimensional electrophoresis after stimulation with 10 nM-angiotensin II or various agents [10 nM-12-O-tetradecanoylphorbol 13-acetate (TPA), 50 nM-A23187, 1 microM-nitrendipine], administered singly or in combination. These patterns were compared with the temporal patterns of aldosterone secretion induced by the same agonists and antagonists. After 1 and 30 min of stimulation with angiotensin II, different patterns of protein phosphorylation were observed. A comparison of these patterns reveals that: the phosphorylation of only one protein was persistently enhanced during the continuous incubation with angiotensin II; the phosphorylation of five proteins was transiently enhanced (at 1 min but not 30 min); and the phosphorylation of three proteins did not occur at 1 min but was seen at 30 min. Addition of the phorbol ester TPA alone, which at 30 min is without effect in enhancing aldosterone production, has no effect on protein phosphorylation. The combined addition of TPA and the Ca2+ ionophore, A23187, which, like angiotensin II, evokes a sustained increase in aldosterone production, reproduced the temporal patterns of protein phosphorylation seen after angiotensin II action. Manipulations (A23187 alone, angiotensin II plus nitrendipine) which evoke only a transient rise in aldosterone production rate induce a transient rise in cellular protein phosphorylation. The 1 min patterns of phosphorylation seen after A23187 or combined angiotensin II and nitrendipine (a Ca2+ channel antagonist) are similar to those observed after 1 min of angiotensin II stimulation. These results suggest that, when angiotensin II acts, the initial cellular response is mediated by a different mechanism than that responsible for the sustained response.     

Relationship between plasma volume reduction and plasma electrolyte changes after prolonged bicycle exercise, passive heating and diuretic dehydration

Plasma volume was decreased by prolonged bicycle exercise, by passive heating in warm water, by sauna dehydration, and by diuretically induced dehydration in eleven well trained subjects. Blood samples from an arm vein were taken before and after this pre-treatment, as well as after a subsequent standard exercise test (SET) on a bicycle ergometer (50%, 70% and 105% of max VO2; the SET with no pre-treatment was used as a control condition. The changes in plasma concentration of Na+, K+ and Cl- were not proportional to the calculated plasma volume changes. The Na+ and Cl- concentrations always increased in the plasma, while plasma potassium concentration was increased after prolonged exercise, but decreased after the other types of dehydrations. The standard exercise test produced a pronounced fall in total calculated plasma potassium and in K+ concentration measured 3-5 min after exercise in all types of experiments. In the standard exercise test the calculated water loss from the plasma volume was relatively large. It amounted to about 2/3 of the total water loss in the standard exercise test and was independent of the pre-treatments.     

A HISTOCHEMICAL STUDY OF ABSCISSION LAYER FORMATION IN THE BEAN

In debladed bean petioles calcium and dry weight increased in the abscission zone during an induction period of 14 hr. Before the microscopic appearance of the abscission layer calcium decreased in the abscission zone and increased in the petiole. Dry matter began to decrease in both the abscission zone and the petiole 24 hr after deblading. The first visual change in the cells of the abscission zone was a swelling of the pectic materials of the cell walls. This was followed by breakdown of other cell wall components, i.e., non-cellulosic polysaccharides and cellulose. The cellulose of the cell walls adjacent and distal to the abscission layer was found to be altered; however, no lignin was present during abscission layer development. The alteration of pectic materials, coupled with breakdown of cell wall components, resulted in the collapse of cells of the abscission layer just prior to separation. Auxin delayed abscission and also delayed the initial increase in calcium, the movement of calcium from the abscission zone to the petiole, and the decrease in dry weight.     

Histochemical changes in the developing abscission layer in fruits of Prunus cerasus L.

Summary Abscission layer formation in the sour cherry (Prunus cerasus L.) during fruit maturation occurred in the transition zone between the fruit and the pedicel. The abscission layer, consisting of 5–8 rows of cells, was first identified by its low affinity for haematoxylin. The walls of cells in the abscission layer contained less total polysaccharides than adjacent cells. The pectins were degraded and the cellulose was partially broken down resulting in cell separation. The Ca level in the abscission zone decreased and Ca and Mg were lost from the walls of cells in the layer during abscission. After the abscission layer formed, cells associated with the layer had a lower capacity to bind ⁴⁵Ca than cells distal or proximal to the layer.Michigan Agricultural Experiment Station Journal Article No. 4607     

The presence of parvalbumin in a nonmuscle cell line attenuates progression through mitosis

Based on studies that have examined the effect of calcium chelators on cells, it has been proposed that this cation plays a role in regulating cell proliferation. In this study a novel approach was used to indirectly examine the role of calcium in cell cycle progression. A cDNA for the Ca2+-binding protein parvalbumin has been expressed in mouse C127 cells, using a bovine papilloma virus-based expression vector. The normal role of parvalbumin is that of a calcium buffer in vertebrate fast twitch muscle, and the C127 cells do not normally express this protein. The presence of parvalbumin had several effects on the growth of C127 cells. The most striking phenotype was an increase in cell cycle duration which analysis showed was the result of an increase the length of G1 and mitosis (predominantly at prophase). Since changes in cell cycle duration typically occur as a result of changes in G1 duration, the observed increase in the length of mitosis is most unusual. The present results indicate that the previously observed increase in the rate of cell proliferation in cells with elevated calmodulin levels is not the result of a general increase in the level of cytoplasmic calcium-binding protein, but is specific to calmodulin. In addition, the results suggest that calcium regulates progression through mitosis by both calmodulin-dependent (metaphase transition) and -independent (prophase) mechanisms.