Recent advances in identifying the functions of gangliosides

The recent development of several new approaches has proven extremely useful in identifying functions for gangliosides, the sialic-acid containing glycosphingolipids. The first is the incorporation of exogenous gangliosides into the plasma membrane of ganglioside-deficient cells. Using this approach, specific gangliosides have been identified as the receptors for certain bacterial toxins and viruses and as important factors in the organization of fibronectin into an extracellular matrix. The second approach has been a ligand blotting technique which allows detection of ganglioside-binding proteins such as toxins and antibodies. Gangliosides are separated by thin-layer chromatography and overlain with the protein of interest. Specific binding of the ligand to gangliosides can then be detected by either direct or indirect methods. The third approach is the use of the B or binding subunit of cholera toxin as a specific probe for endogenous plasma membrane ganglioside function. The ability of the B subunit to alter the growth of cells directly demonstrates a role for gangliosides as biotransducers of signals for the regulation of cell growth.     

Kawasaki disease,or mucocutaneous lymph node syndrome: report of seven cases in North America.

The clinical and laboratory findings in seven children with Kawasaki disease are reviewed. Four of the patients had the more complicated course that has characterized the cases diagnosed in North America. This suggests that the benign forms are often mistaken for other febrile illnesses. The patients were two girls and five boys ranging in age from 4 months to 7 years; six were Caucasian and one was a North American Indian. Fever, redness of the oral mucosa, an erythematous or scarlatiniform rash and cervical adenopathy were seen in all; six patients had the characteristic fingertip desquamation and nonexudative conjunctivitis. Cardiac involvement occurred in four patients, two of whom had coronary artery aneurysm or thrombosis. Arthritis or arthralgia was seen in six patients, and aseptic meningitis occurred in four. Of the three patients with jaundice two underwent laparotomy and excision of a hydropic gallbladder; one of them died from Klebsiella pneumoniae sepsis and disseminated intravascular coagulopathy.     

Subnuclear localization and antitransforming activity of N-myc:beta-galactosidase fusion proteins.

N-myc expression is under stage- and tissue-specific regulation in mammalian development, but its function is totally unknown. We sought agents to block N-myc activity in order to infer from the effect the possible function of N-myc in the apparently complex processes. As candidates for such agents, we tested fusion genes encoding N-myc:beta-galactosidase fusion proteins for their effects on the formation of transformed foci of rat embryo primary fibroblasts as the result of transfection with N-myc and activated H-ras. One of the gene constructs very efficiently antagonized N-myc activity, as assessed by its effect on focus formation, but did not appreciably affect cell viability. The product of this gene was not only targeted to the nucleus but also accumulated in subnuclear loci which may represent the sites where normal N-myc proteins reside. The occurrence of antagonistic effect at a low stoichiometric ratio suggested that the fusion protein gene competed with the N-myc gene in a fashion analogous to a dominant negative mutation.     

Isolation of Temperature-Sensitive Membrane Mutants of Escherichia coli K-12

Mutants with impaired biosynthesis of unsaturated fatty acids or altered metabolism of the phospholipids were isolated at a rather high frequency from a set of temperature-sensitive lysis mutants. It is suggested that preselection for the lysis phenotype makes it possible to isolate several kinds of mutants affected in the integrity of the cytoplasmic membrane.     

Resolution of the conformational distribution and dynamics of a flexible molecule using frequency-domain fluorometry

We report the first resolution of both the conformational distribution and end-to-end diffusion coefficient of a flexible molecule. This molecular information was recovered using only the donor intensity decay in a single solvent at a single viscosity, as observed by the technique of frequency-domain fluorometry. This technique can be extended to measurements of structural fluctuations of biological macromolecules.