Cell Wall Composition of Neurospora crassa Under Conditions of Copper Toxicity

The mycelia of Neurospora crassa grown in the presence of high concentrations of copper were blue in color, but only on a medium containing inorganic nitrate and phosphate as the nitrogen and phosphate sources, respectively. The cell wall isolate of the blue mycelia contained large amounts (12%) of copper and higher amounts of chitosan, phosphate, and amino groups, with a 42% decrease in the chitin content. Although all the glucosamine of the cell wall of control cultures could be released within 6 h of hydrolysis with acid, that of the blue mycelium required prolonged hydrolysis for 24 h. On removal of copper, the cell wall of the blue mycelium could quantitatively bind again to copper as well as to zinc. Although zinc binding was fivefold greater, copper alone was preferentially bound from a mixture of the two metal ions. Supplementation of iron along with copper in the culture medium resulted in the disappearance of the blue color of the mycelium and restoration of normal growth and composition of the cell wall, probably by limiting the uptake of copper from the medium. The possibility of the cell wall being a specific site of lesion in copper toxicity in the mold is discussed.     

Comparison of vascular hemodynamics in experimental models of microvascular anastomoses

Blood flow was measured in the canine saphenous artery using electromagnetic flowmetry. Significant increase in blood flow was noted after occlusion of the distal femoral artery. However, after raising a saphenous island flap there was no significant change in the blood flow before and after distal femoral artery occlusion. The flap peripheral resistance and blood flow were compared after end-to-end and end-to-side anastomosis and no statistical difference was noted.     

Evidence for the presence of inhibitors of mitotic factors during G1 period in mammalian cells

Our earlier studies indicated that the mitotic factors, which induce germinal vesicle breakdown and chromosome condensation when injected into fully grown Xenopus oocytes, are preferentially associated with metaphase chromosomes and that they bind to chromatin as soon as they are synthesized during the G2 phase. In this study, we attempted to determine the fate of these factors as the cell completes mitosis and enters G1. Extracts from HeLa cells at different points during G1, S, and G2 periods were mixed with mitotic extracts in various proportions, incubated, and then injected into Xenopus oocytes to determine their maturation-promoting activity. The maturation-promoting activity of the mitotic extracts was neutralized by extracts of G1 cells during all stages of G1 but not by those of late S and G2 phase cells. Extracts of quiescent (G0) human diploid fibroblasts exhibited very little inhibitory activity. However, UV irradiation of G0 cells, which is known to cause decondensation of chromatin, significantly enhanced the inhibitory activity of extracts of these cells. These factors are termed inhibitors of mitotic factors (IMF). They seem to be activated, rather than newly synthesized, as the cell enters telophase when chromosomes begin to decondense. The IMF are nondialyzable, nonhistone proteins with a molecular weight of greater than 12,000. Since mitotic factors are known to induce chromosome condensation, it is possible that IMF, which are antagonistic to mitotic factors, may serve the reverse function of the mitotic factors, i.e., regulation of chromosome decondensation.     

Disparate functional properties of two interleukin 1-responsive Ly-1+2- T cell clones: distinction of T cell growth factor and T cell-replacing factor activities

We describe the properties of two Ly-1+2- T cell clones (Ly-1.14 and Ly-1.21), which are maintained in long-term culture in the absence of other cell types. The clones require media containing a source of interleukin 1 as well as interleukin 2. They retain physiologic responses to interleukin 1, which is required for optimal production of T cell lymphokines by these clones in response to concanavalin A (Con A). The two Ly-1+2- T cell clones differ in their production of lymphokines after stimulation by Con A. The supernatant of clone Ly-1.21 promotes the proliferation of T cells maintained in long-term culture, induces antibody synthesis in cultures of B cells and antigen, and induces the differentiation of cytolytic cells in cultures of thymocytes and antigen; these assays define the properties of T cell growth factor (TCGF), T cell-replacing factor for B cells (TRF-B), and T cell-replacing factor for cytolytic cells (TRF-C), respectively. In contrast, the supernatant of clone Ly-1.14 contains only TCGF activity and does not promote antibody synthesis by B cells or differentiation of cytolytic cells from thymocytes. The results indicates that TCGF and TRF activities reside on independent, although perhaps related, molecules.     

Chromosomal interchange inEleutherine plicata Herb

Chromosome behaviour at metaphase I and anaphase I of meiosis inEleutherine plicata Herb. (2n=14) is studied. Cells with chromosome associations comprising an association of four long chromosomes, in addition to five bivalents were observed more frequently than those with seven bivalents. it is concluded that the ring of four is due to a segmental interchange between the two long non-homologous chromosome pairs. The ring of four at anaphase I showed delayed disjunction, bridge formation and irregular separation of chromosomes in a number of cells while the behaviour of the other bivalents was normal.     

Effect of excess boron supply on germination and seedling growth of groundnut (Arachis Hypogaea Linn.)

Summary Groundnut (TMV-2) seeds treated with 25 ppm boron solution germinated more quickly than the seeds supplied with deionized water. The borontreated seedlings also elongated rapidly in the initial phase of the growth even though all their different organs contained excess boron contents (with chlorosis in the leaves) than those of the control seedlings. However, the accentuation in the growth of treated seedlings was proceeded only upto a certain period (12 days after treatment); but further stimulation in the later phase of the growth was almost inhibited with ever increasing amounts of boron in the hypocotyl, plumule and leaves (which were severely chlorotic) and even brought about a deleterious effect on the total growth at the end of 21 days when compared to the controls.     

Growth and Endogenous Gibberellin Content of Dormant Groundnut Embryonic-axes as Influenced by Leaching and GA(3)

Leacthing the excised embryonic-axes from dormant groundunt (Arachis hypogaea) seeds resulted in their growth. However, their growth was stunted compared to that of after-ripened ones. It is attributed to (1) the lower amount of gibberellin-like substances in the dry, dormant embryonic-axes than in the after-ripened ones, and (2) the inability of the former to sythesise tbe tibberetllin as indicated by the lower content compared to the after-ripened ones kept in water. Exogenousty supplied GA(3) (0.1 mg/1) increased both the endogenous gibberellin and growth of the dormant, leached embryonic-axes to the level of after-ripened ones.