Stability of tissue culture medium pH as a function of autoclaving,time, and cultured plant material

Autoclaving is a standard procedure for sterilizing nutrient media for plant tissue cultures. Most tissue cultures are grown at pH 5.2 to 5.8 with pH adjustments being made prior to autoclaving. This paper reports that there are significant differences between initial pH levels and pH levels following autoclaving, particularly in the pH range of 5.7 to 8.5. This effect is noted with and without agar. In addition, we report that with time the pH of the medium drifts into the acid range. When Cucumis callus was added to the medium, the pH was changed significantly within 48 hours. The amount and direction (increase or decrease of pH) was significantly correlated with the original pH. This suggests that researchers should be wary of the true pH situation in their medium. In addition, in publications authors should specify whether their medium pH value was determined before or after autoclaving.     

Ganglioside-Induced Neuritogenesis: Verification That Gangliosides Are the Active Agents, and Comparison of Molecular Species

Abstract: Gangliosides were previously reported to induce neuritogenesis in primary neuronal cultures and in some neurally derived cell lines. Because isolated gangliosides usually contain variable quantities of peptides, we investigated the possibility the neurite-stimulating activity could be caused by these contaminants. Ganglioside preparations from bovine brain and other sources were subjected to a three-step purification procedure that eliminated at least 95% of the contaminating peptides. These purfied preparations retained their capacity to induce extensive neurite growth in neuro-2A murine neuroblastoma. Proteolytic digestion and a number of additional procedures were used to reduce residual contamination further without loss of activity. Several crude ganglioside samples had negative effects on neurite development until freed of theri inhibitory factors, which were derived from the tissue and/or introduced during laboratory operations. This was particularly evident for bovine white matter gangliosides whose activity increased in proportion to peptide removal. When carefully purified, virtually all of 11 different gangliosides tested were highly active, with the possible exception of GM4, which demonstrated only moderate activity in a limited number of tests. All of the neutral glycolipids tested, as well as sulfatides and free sialic acid, were inactive.     

Dynamic membrane studies in individuals at risk for Huntington's disease

Lymphocyte plasma membrane dynamics were studied by energy-transfer polarization in twenty-three neurologically normal individuals at-risk for Huntington's disease (HD). The results were compared to 10 normal controls and 10 known HD patients. The normal and HD subjects segregated into two distinct groups. The at-risk group had findings distributed along a continuum with values similar to known HD patients or to normal controls. These findings suggest that further studies of membrane dynamics will contribute to understanding the molecular defect in HD and to the development of a potential molecular marker.     

Loss of the PGE1 requirement for MDCK cell growth associated with a defect in cyclic AMP phosphodiesterase

Prostaglandin E₁(PGE₁), one of the components in the hormone-supplemented, serum-free medium for Madin Darby Canine Kidney (MDCK) cells (Medium K-1), is required for both long-term growth and for dome formation. Variant cells have been isolated from MDCK populations, which lack the PGE₁, requirement for long-term growth in Medium K-1. These variants will be useful in identifying the molecular events initiated by PGE₁ which are necessary for the growth response to be observed. The growth and functional properties of five independently isolated PGE₁ independent clones have been examined. Normal MDCK cells grew at an equivalent rate in Medium K-1 and in serum-supplemented medium; the growth rate was lower in Medium K-1 lacking PGE₁. In contrast, PGE₁ independent clone 1 grew at an equivalent rate in Medium K-1 minus PGE₁, and in serum-supplemented medium. When PGE₁ was added to K-1 minus PGE₁, less growth of PGE₁ independent clone 1 was observed. A similar observation was made with one other PGE₁ independent clone which was studied. A hormone deletion study indicated that PGE₁ independent clone 1 still retained growth responses to the other four supplements in Medium K-1 (insulin, transferrin, T₃, and hydrocortisone). The molecular alterations associated with loss of the PGE₁ requirement for long-term growth were examined. At confluency, all of the PGE₁ independent clones studied had higher intracellular cyclic AMP levels following PGE₁ treatment, as compared with normal MDCK cells. The increased cyclic AMP levels in the variant cells could result from a number of different types of defects, including reduced cyclic adenylic acid (cyclic AMP) efflux, an increased affinity of PGE₂ for the PGE₁ receptor, or a defect in cyclic AMP metabolism. However, in all of the variant clones studied a decreased rate of cyclic AMP degradation by cyclic AMP phosphodiesterase was observed. Thus, the increased cyclic AMP levels in the PGE₁ independent variants may result from alterations which affect cyclic AMP metabolism. The effect of PGE₁ on dome formation by the variant cells was also examined. The frequency of dome formation by PGE₁ independent clone 1 was enhanced in a dosage-dependent manner, like normal MDCK cells. This observation suggests that PGE₁ affects MDCK cell growth and dome formation by different mechanisms.     

Study of Chromosomes in the Newborn after Ultrasonic Fetal Heart Monitoring in Labour

The effect of continuous-wave ultrasound on the chromosomes of newborn infants has been investigated. Twenty-four women were studied during labour. The fetal heart was monitored by a Sonicaid FM2 monitor applied to the abdomen, and continuous monitoring undertaken for intervals varying from 1 hour 5 minutes to 9 hours 25 minutes. There was no increase in the number of chromosome aberrations in cultures of blood taken from the insonated babies when compared with controls.     

Release of Envelope Glycoprotein from Rabies Virions by a Nonionic Detergent

Treatment of rabies virus with the nonionic detergent Nonidet P-40 resulted in solubilization of viral lipids and in a preferential release of the envelope glycoprotein. The other viral proteins and the viral ribonucleic acid remained associated in "core" particles sedimenting at a rate similar to that of intact virions. After fractionation of treated virus by velocity centrifugation in a sucrose density gradient, the amount of residual glycoprotein recovered in the "core" particle fraction and the extent of contamination of the glycoprotein fraction by other viral components were dependent on the ratio of detergent to viral protein used.     

CYTOKINESIS AND PLASMODESMATA IN ULOTHRIX1

Cytokinesis essentially similar to that of vascular plants occurs in Ulothrix, an unbranched filamentous green alga. Plasmodesmata, similar to those of vascular plants, but different from those of many other algae, are also present. Cell plate formation and plasmodesmata also occur in Stigeoclonium, a branched green alga.